There’s no use crying over spilled milk—just turn it into ecofriendly plastic instead. That’s the advice from David Schiraldi of Case Western Reserve University, who has developed a process to make a foam-like material using casein, milk’s most abundant protein, and sodium montmorillonite, a type of clay.

The method is environmentally friendly—its only byproduct is water vapor—and relies on widely available technologies. “It’s something you could almost do in your kitchen,” Schiraldi says.

First, whiz clay and water into a slurry in a blender. In another container, combine casein and water and mix with an eggbeater. Then fold the two liquids together and pour the mix into a mold (the research group gets a kick out of using penguin-shaped ice cube trays, to demonstrate the level of detail the stuff takes on). Flash-freeze, then freeze-dry to draw off the water, and cure in a low oven.

The resulting material “looks, feels, and probably tastes like Styrofoam™,” Schiraldi says. It costs more—milk is more expensive than the petroleum from which Styrofoam is made—but switching to milk-based packaging would add only about 50 cents to the cost of a computer.

An additional advantage is that, unlike many other “green” plastics (such as corn-based polylactic acid, used for disposable drinking cups), the casein-clay foam is biodegradable. About 20 percent of the material decomposed after just 18 days in a landfill, the team reported last year in the journal Biomacromolecules. Yet at room temperature, the foam remains intact for months.

Of course, milk isn’t the answer to all plastics. But Schiraldi estimates that the spoiled or surplus milk that’s currently wasted is enough to produce tens or even hundreds of millions of pounds of the foam per year.

A startup company, Aeroclay, Inc., is working on bringing the product to market. In addition to packaging for high-end electronics, other uses might include insulation for refrigerated shipping containers and perhaps applications in the building industry. “I think that this time next year we may have some early adopters,” predicts Schiraldi. ❧

—Sarah DeWeerdt

Online Map Creation

www.aquarius.geomarde/omc/omc_intro.html

Online Map Creation (OMC) is an amazing resource for anyone needing to make a map. You can create Postscript-formatted maps of just about any locality by inputting geographical coordinates. OMC is a subset of GMT (Generic Mapping Tools) software developed by scientists at the University of Hawaii and NOAA. A variety of projections can be made. Political boundaries, rivers, bathymetry, and topography can be displayed on maps along with tectonic features such as faults and ridges. Once you enter your desired parameters, a full-color (or b/w if you want) map will be presented as a *.gif image or for download in Postscript or Adobe Illustrator format. Step-by-step instructions are provided.

Weeds Gone Wild: Alien Plant Invaders of Natural Areas

www.nps.gov/plants/alien/

Weeds Gone Wild is a project of Plant Conservation Alliance, a consortium of federal and nonfederal agencies dedicated to protecting native plants. Targeting viewers ranging from the general public to researchers, this site provides information on “the serious threat and impacts of invasive alien (exotic, nonnative) plants to the native flora, fauna, and natural ecosystems of the United States.” To that end, the site includes a compiled national list of many invasive plants (aquatics, herbs, vines, shrubs and trees); comprehensive background information on invasive species; illustrated fact sheets with plant descriptions, native range, distribution, and habitat in the U.S.; management options and suggested alternative native plants; and other information. A collection of links to experts and organizations rounds out this well-conceived site.

National Estuarine Research Reserve System (NERR)

www.ocrm.nos.noaa.gov/nerr/

NERR Centralized Data Management Office

inlet.geol.sc.edu/cdmohome.html

Established in 1972 through the Coastal Zone Management Act (CZMA), the National Estuarine Research Reserve System (NERR) is a network of protected areas representing different types of estuaries and biogeographic regions. Operated by coastal states with input from local communities and regional groups, NERR studies address coastal watershed management issues. The homepage provides an overview of the NERR System with links to specific information on (most) reserves, detailed case studies on six focal reserves, publications and research resources, educational materials, and links to related resources. For reserve data and data on water quality (and associated metadata), see the NERR Centralized Data Management homepage.

Northwoods Wildlife Habitat Database

www.ncrs.fs.fed.us/northwoods/index.html

Created through a joint effort of the USDA Forest Service’s North Central Forest Experiment Station (NCFES) and seven national forests in the Upper Great Lakes Region, Northwoods is a wildlife habitat database featuring “information about the habitat needs of 389 species of reptiles, amphibians, birds, and mammals in the Upper Great Lakes Region.” The database compiles common and scientific names, species occurrences in 20 aquatic and terrestrial habitat types, species abundances and seasonal use in seven national forests, and species conservation status. The Northwoods database is available in tab-delimited ASCII file format.

2000 IUCN Red List of Threatened Species

www.iucn.org/redlist/2000/index.html

IUCN, the World Conservation Union has spent the past four decades working to provide objective, scientifically based information on the current status of the earth’s threatened biodiversity. To that end, IUCN has just released its much-anticipated Red List of 2000, listing the more than 11,000 species of the earth’s plants and animals that face high risk of extinction in the near future. Since the IUCN’s last assessment in 1996, over 200 new animal species have become threatened, almost all as a result of human activities. The searchable IUCN Red List Web site has ten sections: Introduction, Data Organization, Red List Programme, Summary Statistics, Sources & Quality, Categories & Criteria, Habitat Types, Threat Types, Image Captions, and References. Two search options (regular and expert) enable users to search by taxonomic classification, with four additional modifiers: Red List Category, Country, Geographic Region, and/or Marine Region. Typical returns include taxonomic details (scientific classification and common name), assessment information, distribution (by country), and summary documentation (Biome). This seminal resource represents the most current and reliable information of its sort and is a “must read” for any one working on ecology or conservation.

Water Librarians’ Homepage

www.wco.com/~rteeter/waterlib.html

Robert Teeter, librarian at a California water agency, has put together this metasite containing a variety of useful links in the field of water resources along with other library-related links. Agencies, databases, publishers, organizations, libraries, mailing lists, and more are featured. Teeter has organized the links by page type and indicates which sites are newly added or personal favorites. Just a few examples of links at the Water Librarians’ Homepage include: Waterfront (an information source on water conservation initiatives taking place in Winnipeg, Canada), The American Water Resources Association, and The Environmental Professionals’ Homepage (providing links to primary sources of environmentally-related information). This is an excellent tool for academics, professionals, and librarians in the field of water resources and also environmental engineering.

General Multilingual Environmental Thesaurus (GEMET)

www.epa.gov/oiamount/termsys.htm

The GEMET Approach

(v 2.0) [.pdf]

www2.mu.niedersachsen.de/cds/webpages/6.htm

Differences in terminology and language can be major barriers to effective international collaborations — such as in the development of (often delicate) environmental protection agreements. To reduce these barriers, several European and U.S. environmental agencies have joined forces to develop a common terminology system, called GEMET. This General Multilingual Environmental Thesaurus (GEMET) is “a vocabulary of more than 6,500 controlled terms (keywords), representing broad environmentally significant concepts.” The first web site, from the U.S . Environmental Protection Agency, describes GEMET and the importance of this collaborative project. The second web site, provided by the Ministry of Environment of Lower Saxony, serves as a gateway into GEMET. Here users will find seven .pdf documents which are the various components of the thesaurus, including the impressive multilingual list of descriptors. GEMET 2.0 was edited in British and American English, with equivalents in ten European languages.

Biological Conservation Newsletter of the Smithsonian Institution

www.mnh.si.edu/botany/bcn

This newsletter contains articles on conservation research and activities of the Smithsonian Institution. Also included are current news items, information on new publications, fellowships and grants, job announcements, and meetings. The Conservation Bibliography includes over 7,000 references to literature on conservation biology. All issues from the past nine years have been archived and are available for viewing. You can subscribe to the BCN listserv, a service that will notify readers when new issues are posted. To subscribe, send an e-mail message to email hidden; JavaScript is required containing only the following in the body of the text: SUBSCRIBE BCN FIRSTNAME LASTNAME.

National Invasive Species Management Plan

www.invasivespecies.gov/council/nisc/nmp.html

In February 1999, an Executive Order by President Clinton established the National Invasive Species Council (NISC) to take a leadership role in dealing with invasive species issues. As part of that order, NISC has prepared a plan “to minimize the economic and ecological impacts and the harm to animal and human health associated with invasive species.” This document, “National Management Plan: Meeting the Invasive Species Challenge,” is posted on the NISC web page.

Erratum: We apologize for the misspelling of Scott Johnston’s name (Building a Species Recovery Program on Trust) in our first issue.

Maine’s Kennebec River was renowned for its magnificent runs of salmon, sturgeon, and other anadromous fish until their migration was blocked by the 1837 construction of Edwards Dam in Augusta. Opposed by citizens of Maine before it was even built, the privately-owned dam stood for more than 160 years despite a number of attempts to remove it. Then in the early 1980s, a handful of anglers in the Kennebec Valley chapter of Trout Unlimited had the wild — and ultimately successful — idea of convincing the Federal Energy Regulatory Commission to deny the relicensing of Edwards Dam.

October 2000 marked the first anniversary of the dam’s complete removal, and the story of how this idea became a reality shows the importance of doing everything you can think of to achieve your goal, of forming alliances with key stakeholders, and even of compromising with the opposition. The 10-plus years of intensive effort were well worth it: so far the recovery of the newly-undammed stretch of the Kennebec River has exceeded all expectations.

The Kennebec flows 230 miles from Moosehead Lake to Merrymeeting Bay, which is on the coast of Maine near Bath and is New England’s largest freshwater tidal estuary. The unique combination of these extensive fish nursery grounds with the Kennebec’s extensive spawning grounds gave the river one of the most diverse and abundant fish populations in the region. All 10 of the anadromous fish species native to Maine spawned in the Kennebec. There were so many alewives (a large herring) that they “crowded one upon another to the depth of a foot,” according to James Sullivan’s 1795 History of the District of Maine. Salmon were so plentiful that a contract between a hay farmer and his laborer stipulated that they could only be served once a day.

The Kennebec’s rich anadromous fish populations were devastated by Edwards Dam, which was originally built to power a saw mill and provide passage for barges. The site was right where the tidal influence ends, about 40 miles from the river’s mouth on the Atlantic Ocean, which meant that the dam blocked virtually all fish migration. Although the dam initially had a fish ladder, floods washed it away the very next spring. In defiance of a 1797 Commonwealth requirement that dams on the Kennebec have fish passages, the first owners of Edwards Dam refused to replace the ladder, and subsequent owners all followed suit. Even if fish had been able to pass Edwards, many would not have been able to breed because the 917-foot-wide, 25-foot-tall dam inundated the river’s most important spawning habitat, the 17-mile stretch between Augusta and the next dam in Waterville.

Edwards Dam flooded more than 1,000 acres, turning them into an aquatic wasteland. Too deep to be a river and yet too shallow to be a lake, the impounded area favored small mouth bass and other opportunistic species that aren’t picky about where they live. But most of the bottom-dwelling organisms at the base of the food chain could no longer survive.

Because more than 90 percent of New England’s anadromous fish spawning grounds are gone, fisheries biologists have repeatedly pressed for the removal of Edwards Dam. For instance, they tried to get the dam removed in 1974 when a flood washed out a 150-foot section; but their pleas went unheeded, and the dam was rebuilt the following year.

Then in 1986 the Maine Department of Marine Resources began developing a plan to restore anadromous fish in the Kennebec. By 1987 the owners of seven dams upriver from Edwards had agreed to install fishways for alewife, American shad, and Atlantic salmon. However, the upriver dam owners’ willingness to help had no practical effect because the Edwards was the first dam on the river and its owners refused to participate.

Used in various ways during its long history, Edwards Dam began generating electricity in 1984. While extremely profitable to the owners, who had a contract guaranteeing them several times the going rate for electricity until 1998, this use ultimately led to the dam’s downfall. Hydroelectric dams are regulated by the Federal Energy Regulatory Commission (FERC), and a 1986 amendment to the Federal Power Act required the FERC to give equal consideration to generating power and to preserving environmental quality when considering a dam’s license.

Hydrodam licenses last up to 50 years, and Edwards Dam was coming up for relicensing in 1993 — providing a window of opportunity for removing it. In hopes of convincing the FERC to deny relicensing, in 1989 the Kennebec Valley chapter of Trout Unlimited formed the Kennebec Coalition with four national conservation organizations, American Rivers, Atlantic Salmon Federation, Natural Resources Council of Maine, and Trout Unlimited. The Coalition knew their chances were slim. “Back then, no one else wanted to touch dam removal,” says American Rivers coalition member Steve Brooke.

The first step in the process of hydrodam relicensing is for the owners to file an application with the FERC two years in advance. In 1991, the owners of Edwards Dam applied to extend their contract for 50 years and to more than triple their hydropower capacity. The dam owners were also required by law to notify federal, state, and local natural resources agencies.

The second step in the process is for the FERC to evaluate the hydrodam’s impact on the environment, which involves preparing an Environmental Impact Statement and collecting comments from resource agencies. The FERC also had to consider a Kennebec River restoration plan that the State of Maine Planning Office had developed under the direction of the state legislature.

It soon became clear that the Kennebec Coalition had some powerful allies. Then Governor John McKernan of Maine, the state legislature, and the U.S. Fish and Wildlife Service all called for the dam’s removal. “From the beginning, we favored dam removal because a number of species don’t use fishways — they can work for salmon because they’re attracted to flowing water but sturgeon migrate along the bottom,” says Gordon Russell of the U.S. Fish and Wildlife Service in Old Town, Maine. Of the 10 anadromous species that historically spawned in the Kennebec River, four do not use fish passages, striped bass, rainbow smelt, and both Atlantic and shortnose sturgeon.

However, in 1996 the FERC issued a preliminary recommendation to relicense Edwards Dam with the stipulation that the owners build a fish passage specified by the U.S. Fish and Wildlife Service. Under the Federal Power Act, the Service has the authority to require fishways for dams under FERC jurisdiction.

In the meantime, the Kennebec Coalition was making an airtight case for removing Edwards Dam. “It was not a one-sided analysis,” says coalition member Margaret Bowman of American Rivers in Washington, D.C. “We carefully examined the pros and cons, documented the benefits, and addressed the negative issues to convince others that removal was the best option even in the worst-case scenario.”

The Kennebec coalition showed that removal was the best alternative on seven fronts: economic, engineering, legal, philosophical, political, scientific, and social. For instance, the fish passage specified by the U.S. Fish and Wildlife Service would have cost $9 million and would have helped restore only three of the river’s anadromous fish species, while removing the dam would have cost 40% less and would have helped restore all 10 species.

Then in 1997 the seemingly impossible happened. In its final Environmental Impact Statement, the FERC recommended removing Edwards Dam. Ruling that the economic and environmental benefits of dam removal exceeded the hydropower benefits, the FERC ordered removal at the owners’ expense.

Not surprisingly, the owners of Edwards Dam balked. They were in a no-win situation: keeping the dam would have meant paying for the fish passage as well as earning less when their lucrative utility contract expired in 1998, but giving up the dam would have meant paying for and being liable for its removal. As an added complication, the City of Augusta had been co-licensee of the dam since 1992 and was loathe to give up its share of the hydropower revenue.

To try to keep the dam owners and the City of Augusta from going to court and holding up restoration for who knows how long, the Kennebec Coalition approached the State Planning Office and asked if the State would play an active role in arriving at a settlement. The new governor, Angus King, agreed, and State Planning Office director Evan Richert and the coalition led negotiations for the State. “We needed to find a way where no one party was unduly injured,” says Richert. For its part, the State of Maine offered to take ownership of Edwards Dam, as well as both the responsibility and liability for removing it.

The next step was to build trust among the negotiating parties. “The Governor talked to the dam owners and the City to gain their confidence. He built rapport with the dam owners and even went to an Augusta City Council meeting,” says Richert.

But trust only goes so far, and in the end it all came down to money. Funding was a stumbling block until the Kennebec Coalition found a creative solution. Extending their focus beyond the 17-mile stretch impounded by Edwards Dam, the coalition cut deals with stakeholders both up and down the river.

The seven upriver dam owners and Bath Iron Works, a ship builder at the mouth of the Kennebec, agreed to pay the nearly $3 million cost of removing Edwards Dam as well as to fund a $4.85 million, 15-year program to restore anadromous fish to the river. In exchange, the upriver dam owners got to renegotiate their agreement to install fish passages. Rather than having to build them in 1998, they can now wait until the fish return. Bath Iron Works got to use its contribution to restoring the Kennebec as partial mitigation for expanding its shipyard into several acres of coastal wetland. “The Kennebec Coalition was sophisticated; they knew when to compromise. Being absolutist would have delayed restoration,” says Richert.

As co-licensee of Edwards Dam, the City of Augusta also needed something to make up for the revenue it would lose. To make Augusta happy, the State Planning Office took responsibility for the dam’s former mill site, a mildly contaminated brownfield, restored it, and then gave it to the city. The Planning Office also helped Augusta get grants to improve its riverfront. With all obstacles gone at long last, the settlement to remove Edwards Dam was signed in 1998, and the dam was removed between July and October 1999.

The newly-undammed stretch of the Kennebec River rebounded rapidly. There has been a tremendous increase in the diversity and abundance of bottom-dwelling invertebrates such as caddis, may, and stone fly larvae. The Maine Department of Environmental Protection found that diversity doubled from about 6 to 12 species per sample, and that abundance increased about 40-fold from roughly 50 to nearly 2,000 per sample.

The Department of Environmental Protection uses these bottom-dwelling invertebrates as indicators of freshwater quality and rates river water on a scale of A to C. Before Edwards Dam was removed, the Kennebec sometimes failed to meet the criteria for Class C. Now the river’s water quality has risen to a solid Class B.

Moreover, anadromous fish have begun returning to the Kennebec for the first time since the construction of Edwards Dam. While it is too soon for comprehensive data on the fishes’ recovery, what the Maine Department of Marine Resources does know is encouraging. Within three months of the dam’s removal, schools of alewives and striped bass migrated past the former dam site. Within a year, American bass, Atlantic salmon, shad, and sturgeon were also migrating up the river.

“It came as a surprise that the river rebounded so quickly and dramatically,” says Kennebec Coalition Coordinator Betsy Ham, who is the River Advocate for the Natural Resources Council of Maine. “No one was sure what would happen; there’s no precedent for a river of this size. Now we know that if left to its own devices, a river can come back to life.”

While this was hardly the first time that a dam has been removed in the U.S., the removal of Edwards Dam marked many firsts. Besides being one of the largest dams ever removed, Edwards is the first hydrodam that has been removed in the U.S. More significantly, this is the only time the FERC has ruled that the environmental costs of a hydrodam outweighed the economic benefits. “The FERC decision fell in favor of the environment for the first time,” says American Rivers coalition member Brooke.

Even more significantly, this is the first time the FERC has ordered a dam removed against the owner’s wishes. “Prior to Edwards, the FERC didn’t think it had that authority. This established that it does have the authority to remove dams,” says American Rivers’ Bowman.

And that has changed everything in the world of dams. Now, instead of being considered a wild idea, removal is a standard option when evaluating dams, says Bowman. Take the four hydrodams on the Snake River in Washington State. While the dams provide the cheapest electricity nationwide, conservation groups are calling for their removal because they also block the migration of threatened salmon. “The battle over the Snake River dams wouldn’t even be happening without the precedent of removing Edwards Dam,” says Bowman.

The implications for conservation practitioners are equally profound. “Don’t be afraid to think big,” says Bowman. “Dam removal was an unheard of concept 10 years ago. Then a group of people in Maine dared to ask the question ‘What if we removed the dam?’ Who knows what that wacky question is today?”

For more information on the removal of Edwards Dam, go to American Rivers Online, “Edwards Dam Removal, Kennebec River, Maine.”

www.americanrivers.org

At the same web site, for more information on dam removal in general, go to “Dam Removal Success Stories: Restoring Rivers through Selective Removal of Dams that Don’t Make Sense.”

About the Author
Robin Meadows is a freelance science writer specializing in conservation.

Winter 2001 (Vol. 2, No. 1)

Roads and conservation just don’t mix. Already blamed for spreading invasive species and increasing sediment in steams, roads can also block gene flow in animal populations, according to new research in the August issue of Conservation Biology.

This is the first study showing that roads can isolate populations genetically. There are lots of natural barriers to gene flow in populations, including rivers, mountains, and volcanic eruptions. Biologists have speculated that roads also block gene flow because many species avoid crossing them. To facilitate animal movement across roads, European conservationists have pushed for “green bridges,” but building them has been contentious in Germany and Switzerland.

“There is always a fight during the environmental impact assessment about including green bridges, including when a new highway is built,” says Gabriele Gerlach of the Universitat Konstanz in Konstanz, Germany, who did this study with her colleague Kerstin Musolf.

To determine whether roads actually are genetic barriers and so warrant green bridges, Gerlach and Musolf compared DNA variations in small rodents called bank voles that lived on either side of three types of roadways: a 20-foot-wide railway, a 33-foot-wide country road, and a 164-foot-wide four-lane highway. These roadways were in large forested areas of southern Germany and Switzerland and were at least 25 years old, corresponding to at least 25 generations of bank voles.

While there was no genetic difference in the voles living across the railway or the country road, the voles living on either side of the four-lane highway were so distinct genetically that the researchers concluded there was little gene flow between them.

In small populations, low gene flow can decrease genetic diversity and fertility, thus increasing extinction risk. As the density of roads increases, so does the likelihood that animals will subdivide into small, isolated populations that ultimately die out. To help keep roads from blocking animal movement, Gerlach and Musolf call for more green bridges and wildlife underpasses. To encourage animals, from hedgehogs to badgers to wild boars, to use them, green bridges should be wider than 164 feet and planted with hedges and shrubs.

For more Information
Gerlach, G. and K. Musolf. 2000. Fragmentation of landscape as a cause for genetic subdivision in bank voles. Conservation Biology14(4):1066-1073.

Gabriele Gerlach (email hidden; JavaScript is required)

Kerstin Musolf (email hidden; JavaScript is required)

Winter 2001 (Vol. 2, No. 1)

Many conservation biologists have been skeptical of population viability analysis (PVA), which wildlife managers use to predict species’ extinction risks and rank management options. But in a pair of recent papers, researchers show that while some PVA models can underestimate extinction risk, they are reasonably accurate when used correctly.

The study showing that PVA can underestimate extinction risk was by Barry Brook, then at Macquarie University in Sydney, Australia, and his co-authors, and is in the June 2000 issue of Conservation Ecology. This is the first standardized comparison of widely used PVA packages.

The study showing that PVA predicts population declines accurately was by Brook et al. and is in the 23 March issue of Nature. This is the first comprehensive evaluation of the reliability of PVA predictions.

While previous PVA comparisons showed that the predicted extinction risk sometimes varied widely from package to package, the inputs in these comparisons were not standardized. In their Conservation Ecology paper, Brook and his colleagues used six life-history types representative of those modeled in recent PVAs and analyzed each with five widely used PVA packages (two individual-based packages, GAPPS and VORTEX, and three matrix-based packages, INMAT, RAMAS Metapop, and RAMAS Stage). Five of the life-histories were based on real populations (including a reptile, birds, and mammals) with detailed monitoring and ecological data. The sixth life-history was hypothetical and represented a bird- or mammal-like species with low growth rate and low levels of environmental variation.

Brook and co-authors found a striking discrepancy between the individual-based and the matrix-based PVA packages: the extinction risk predicted by the former was an average of 16 percent higher than that predicted by the latter. One of the biggest differences between these two types of PVA packages is that individual-based models consider the sexes separately and so account for variation in sex ratio, whereas standard matrix-based models consider the sexes together and so do not account for variation in sex ratio.

To test whether this difference explains the 16 percent discrepancy in predicted extinction risk, the researchers used RAMAS Stage, which is matrix-based but can consider the sexes separately and so account for sex ratio variation. When RAMAS Stage was set to consider the sexes together, the predicted extinction risk was 1.6 percent — similar to that of the standard matrix-based models. In contrast, when RAMAS Stage was set to consider only females, the predicted extinction risk was about 13 percent — similar to that of the individual-based models. Because the discrepancy in predicted extinction risk essentially disappeared when RAMAS Stage was set to account for sex ratio variation, the researchers concluded that the standard matrix-based packages were underestimating the true extinction risk.

“To keep matrix-based PVA packages from underestimating the extinction risk, managers using matrix-based PVA packages should consider only the sex that is limiting for breeding,” say Brook and his co-authors. While this generally means considering only females, there are two exceptions. First, only males should be considered for those rare species in which males are the limiting sex, such as the emu Dromaius novaehollandiae, where the male incubates eggs from many females and rears the chicks himself. Second, both sexes should be considered for monogamous species because in this case either can be limiting.

As long as the PVA packages tested were used appropriately, the researchers found that they predicted very similar extinction risks, suggesting that all five are valid for comparing management options.

Brook et al. support this conclusion in their Nature paper. They tested accuracy of the same five PVA packages with existing data from long-term studies of 21 wildlife populations ranging from 11 to 57 years. They used the first half of the data from each population to set the model parameters and the second half to test the accuracy of the model predictions. The results showed that the population declines predicted by the PVA packages closely matched the declines that had actually occurred.

“PVA predictions are surprisingly accurate, given adequate data,” says Brook. “Our research validates PVA as a useful tool for managing threatened populations.”

Brook is now at Northern Territory University in Darwin, Australia; his co-authors on the Conservation Ecology paper are Mark A. Burgman of the University of Melbourne, Victoria, Australia, and Richard Frankham of Macquarie University in Sydney, Australia.

Brook’s co-authors on the Nature paper are Julian O’Grady, Andrew P. Chapman, and Richard Frankham of Macquarie University in Sydney, Australia; Mark A. Burgman of the University of Melbourne, Victoria, Australia; and H. Resit Akcakaya of Applied Biomathematics in Setauket, New York.

Further Information:
Brook, B.W., M.A. Burgman, and R. Frankham. 2000. Difference and congruencies between PVA packages: the importance of sex ratio for predictions of extinction risk. Conservation Ecology 4(1):6.http://www.consecol.org/vol4/iss1/art6

Brook, B.W., et al. 2000. Predictive accuracy of population viability analysis in conservation biology. Nature 404:385-387.

Barry W. Broo (email hidden; JavaScript is required)

Which invasive species cause the most serious ecological threats? And, which are most amenable to management? With more than 100 alien plants on many wildland sites and the daunting prospect of long-term expensive management strategies, these are not academic questions. Many managers may be inclined to just throw up their hands and give up.

The alien plant ranking system (APRS) is an automated web-based resource that can help managers work through tough decisions about prioritizing the management of alien plants. APRS helps identify those species that have the most serious impact—those on site of limited distribution or off site with a high potential to invade, as well as those that appear innocuous (usually the majority). APRS also helps managers assess the feasibility of controlling the most threatening species.

The system guides managers through 25 questions in three sections relating to individual species: (1) current level of impact, (2) potential of a species to become a problem, and (3) feasibility of control. The sections include questions about the distribution and abundance of species, the number of seeds they produce, and their dispersal capabilities. There are also questions about whether a species is known to seriously impact other sites. When all the alien species known to occur on or adjacent to a site have been scored, the system ranks them according to current impact, potential impact, and feasibility of control.

Using the System

Step 1. List known and potential alien plants in the area. Good places to start include species lists and research reports, site-specific herbarium specimens, and a preliminary site survey. To determine which species are alien, each plant on the list should be checked against floras of the area.

Step 2. Survey the site. This more thorough site survey can be either a systematic walk through or a quantitative spatially-based sampling scheme such as a GIS-based survey. Though more expensive, GIS-based surveys show distribution and abundance information that can be correlated with disturbances, roads, and vegetation type, for example. GIS sampling schemes also can serve as the basis of invasive species monitoring programs.

Step 3. Search the literature. Managers will need to do a comprehensive literature search to answer the questions on the ecology, biology, and control methods for each alien species found. This is the most time-consuming step in the process. To help, the U.S. National Park Service has begun to front-end load data on alien species and prepare fact sheets for species already determined to be invasive.

Step 4. Fill out the data sheets. The system now has enough information to create graphs showing species scores and management status (Figure 1).

Step 5. Interpret the results. The final and most important step is to incorporate the outputs (listed below) in designing alien plant management strategies and action plans.

Considerations and Limitations

Although the APRS was initially designed to help make management decisions on individual sites, it has since been adapted for the State of Minnesotañand could be further adapted for use on a regional or even national scale. However, managers should bear in mind that results are good only for a limited space and time. Data should not be extrapolated from one site to another, nor should data be considered to reflect current conditions for a period of more than five years.

Another limitation of APRS is that many users have had difficulty responding with confidence to all questions. For some species, for example, seed longevity in the soil is not known; whether a species can be successfully controlled, what the side effects of control may be, or what the cost will be in time and dollars are other examples. Other users have had difficulty dealing with scale and heterogeneity issues. Alien species may be prominent in one location or community within a site and scattered or absent in others. Yet APRS asks for just one response. Lessons from use of the APRS in the Channel Islands National Park provide a good example of how to deal with this particular problem. As the distribution and abundance of alien species varied highly between islands, managers decided to rank species by island rather than for the entire park.

As is the case with most tools, the quality of the product is dependent on the skill of the user. The person who actually applies the system should have skills in plant ecology and be knowledgeable of the area. While the system helps the manager decide which species need what management efforts, it does not tell the manager what that management effort should be.

Most site managers are looking for a decision tool that is quick and cheap to apply and will provide all the answers. Unfortunately, APRS is neither. While more efficient survey methods and species fact sheets are being developed, managers still need to conduct thorough site surveys and often intensive literature searches. However, the outputs of the APRS do help managers design and build an invasive plant management plan. Furthermore, the system is purposely designed to allow flexibility in applying the information to a specific site with its own unique ecological and political setting.

For more Information:

Ron Hiebert

Colorado Plateau Ecosystem Studies Unit,

Northern Arizona University, P.O. Box 5765

Flagstaff, AZ 86011-5765

email hidden; JavaScript is required

APRS is based on the system presented by R. Hiebert and J. Stubbendieck in the Handbook for Ranking Exotic Plants for Management and Control. Automation and revision of the system was a team effort involving Diane Larson and Jim Bennett of the USGS Biological Resources Division; Karl Beres from Ripon College; Diane Beres, David Lime, Anthony Starfield, and Jerrilyn Thompson from the Univeristy of Minnesota; and Ron Hiebert of the National Park Service.

Visit the APRS Web Site:
www.npwrc.usgs.gov/resource/2000/aprs/APRS.HTM

Many of us do best in familiar environments, and the same is true of plants used for restoring ecosystems, according to new research in the August issue of Conservation Biology. This is the first study showing the importance of both genetic and environmental similarity when transplanting wild plants.

While many restoration projects use native plants, they fail to account for genetic and environmental differences between the transplants and local populations. “Mis-matching source populations may lower the success of restoration,” says Arlee Montalvo of the University of California at Riverside, who did this work with her colleague Norman Ellstrand.

Montalvo and Ellstrand tested the importance of the source of plants used for restoration with deerweed, a yellow-flowered member of the pea family that grows in southern California’s coastal sage scrub. They chose deerweed because, although it varies geographically (one variety grows primarily along the coast, and the other grows inland), the two varieties have been used indiscriminately for restoration projects.

The researchers collected deerweed seed from 12 areas with different climates and soils and then transplanted seedlings from each of the 12 sources into two experimental gardens within native coastal sage scrub, one coastal and the other inland (with hotter summers, cooler winters, and less rain). They measured the distance between transplant sources and experimental gardens in three ways: geographically, genetically, and environmentally. They measured the success of transplanted seedlings by factors including survival, size, and flower production.

The results showed that whereas geographic distance had little effect on transplant success, transplants did better in the experimental garden that was genetically and environmentally closer to the area they originally came from. Specifically, in the coastal garden, transplants did better when they were genetically similar to the local deerweed. In the inland garden, transplants did better when they were both genetically and environmentally similar to the local deerweed.

This study shows that the common practice of restoring ecosystems with plants from similar communities does not go far enough. To increase the success of restoration projects, Montalvo and Ellstrand recommend choosing transplant sources that are also ecologically similar.

Further Information:
Montalvo, A.M., and N.C. Ellstrand. 2000. Transplantation of the subshrub Lotus scoparius: testing the home-site advantage hypothesis. Conservation Biology 14(4):1034-1045.

Arlee Montalvo (909-787-5405) email hidden; JavaScript is required

Norman Ellstrand (909-787-4194)   email hidden; JavaScript is required

Not far from the U.S./Mexico border, Mark Larkin grows a dozen vegetable crops as well as fruits and pasture grasses. One season he noticed that honeybees were nearly absent from his fields and orchards along the Rio Santa Cruz floodplain. Larkin is what you might call a stripped-down farmer—a short crew cut, sleeveless T-shirt, a doorless pickup, minimal chemical use, a small tractor or an occasional draft horse—but no farmer wants his land stripped of its pollinators.

News of declining birds and bees does not make many farmers happy, let alone one who grows a diversity of crops that benefit from—and in some cases require—cross-pollination for abundant harvests. Parasitic mites unknown to North America’s beekeepers prior to 1985 had rapidly spread across the country, devastating hive after hive of both managed and feral honeybees (1). In fact, Mark and his neighbors began to witness a paucity of wild and managed honeybees in their fields about five years ago. At the same time, biologists documented that such declines were not restricted to mite-infested bees, but that they also affected other pollinators formerly found in abundance in the binational corridor of the Rio Santa Cruz and in other riparian habitats spanning the U.S./Mexico border. Since 1995, U.S. and Mexican farms and ranches have suffered what the USDA has called the worst “pollination crisis” in American history (2). In 1998, the Society for Conservation Biology approved its first commissioned paper, which addressed the potential causes and consequences of pollinator declines on biodiversity and food yields, finding evidence that such declines were caused by inappropriate pesticide use, genetically-engineered crops, habitat conversion, and fragmentation (1).

Most farmers like Mark recognized that pollination is one of nature’s services essential to forage and crop production. Yet, few were in such a unique position to verify what relatively inexpensive land use changes could do to restore and enhance pollinator diversity and abundance. Mark had already been collaborating with ecologists to determine the effects of treated sewage effluent and rest-rotation grazing on riparian restoration, and he allowed us to initiate pollinator population monitoring just as the managed bee colonies on the farm were removed, and the last feral colony went into demise. Within three years, Mark knew that he never had to rent managed colonies of honeybees again to guarantee sufficient fruit yields; between his riparian restoration efforts, his maintenance of hedgerows and woodlots, and his minimal use of toxins in integrated pest management, native pollinators were provided with enough nectar and nesting habitat to ensure that his fruits and vegetables—as well as many wild plants—had adequate pollination services provided to them. At the same time, Larkin could rightfully claim that his farm was part of a restored migratory corridor that benefited many forms of wildlife, not just pollinators.

Such success stories on private lands often get overlooked, especially in contrast to more glamorous conservation efforts that focus on establishing new protected areas. Yet, as important as reserves are, without good stewardship of the private lands that lie between them, they are inadequate. Private lands (including many farms) provide the “stepping stones” or stopovers for the 300-some migratory species that move between the reserves of tropical Mexico and those of the temperate and boreal U.S. In addition, pollinator habitat restoration can result in direct benefits to farmers over and above the presence of “watchable wildlife.” If we are to promote participation of Mexican and U.S. farmers in protecting and restoring wildlife corridors, the economic benefits of pollinating services provided by these corridors are not a mute point. Here is a land management action that can bridge rather than divide the conservation sector and food production sector of our societies.

The Ecological Roles of Pollinator Corridors

Conservation corridors typically conjure up images of continuous linear habitats or greenways that provide for the movements of large predators and other wide-ranging species. In contrast, migratory corridors for winged pollinators might be more aptly described as a mosaic of stepping stones within a larger matrix, with each stone a stopover that migrants use for “refueling” while in transit along 2000-6000 km flyways. The “glue” providing the connectivity in this mosaic is the shared presence of certain flowering plant genera and the mobile pollinators that visit them.

For example, lesser long-nosed bats (Leptonycteris curasoae) use dense stands of columnar cacti, agaves, and morning glory trees near cave roosts as stepping-stones on their northward flight from Jalisco to southern Arizona. Many of these nectar-producing plants visited by long-nosed bats are patchily distributed succulents that favor hot, rocky hillsides and cliffs. The frequency of these patches maybe just as naturally limiting to nectarivorous bats as the availability of roosts in caves and rock shelters. If this hypothesis is true, it suggests that migratory pollinators such as long-nosed bats moved considerable distances to find one stepping-stone after another, even before the intervening matrix was degraded.

Donna Howell, a bat ecologist, may have been the first to explicitly suggest that at each stepping stone along a migration route, “It is not uncommon to find several bat-pollinated species in association [with one another at the same site] exhibiting similar phenologies.” From winter through late spring, these clusters of bat-pollinated plants bloom sequentially from south to north, creating the effect of a blooming wave cresting northward (3). Near simultaneous blooming of several nocturnally flowering species at the same site has the effect of presenting a concentrated energy source to nectar-feeding migrants, which keeps them at a particular stopover roost until the nectar resources there begin to decline. Then the pollinator population is “forced” northward to seek the next emerging bloom in the northward-reaching wave.

A nectar trail is the entire circulation pattern that pollinators follow as they migrate from one sequentially blooming plant population to the next (3). The loosely co-evolved relationships between migratory pollinators and plant populations contributing to the blooming wave may be thought of as sequential mutualisms. Should one or more of the plant mutualists be eliminated from the sequence by habitat destruction, bad weather, competition, pests, or diseases, pollinator nutrition and movements may be disrupted to the extent that they cannot visit other mutualists.

A sequential mutualism implies that an animal may be linked in space and time with several flowering plant populations, and in the case of lesser long-nosed bats, may move pollen and seeds between them. Obviously, because the plants are sessile but the pollinators are not, nectarivorous bats, hummingbirds, doves, butterflies, and moths serve as mobile links among plant populations in different landscapes, facilitating pollen and gene flow over considerable distances. Similarly, lesser long-nosed bats and white-winged doves (Zenaida asiatica) also facilitate seed dispersal and spatial mixing of genotypes from geographically isolated populations, thereby serving as mobile links between cactus populations during two different phases in the plants’ life cycle.

While migratory pollinators ensure landscape-level linkages among many different plant populations, many non-migratory pollinators visit these same flowers and secondarily benefit from genetic mixing stimulated by the migrants. Should the landscapes that are linked by pollinators fall within officially designated wildlife reserves or protected areas, these migrants may be among the few mobile links that visit most or all units in a regional reserve network.

Vulnerability of Pollinator Corridors

In arid and dry subtropical landscapes, farmlands found between protected areas can serve either as oasis-like stopovers for these migrants (4) or as barren, chemical-ridden sites that further stress pollinators during the most energy-intensive phase of their annual cycle (4, 5). Over the last half century, millions of hectares of desert and thornscrub vegetation in western Mexico and the Southwest U.S. have been converted to chemically intensive agriculture or to pastures of exotic grasses, creating 100-200 km stretches of flyways devoid of suitable forage and roost sites for nectarivores. We are only beginning to fathom the long-term effects on migratory bats, doves, hummingbirds, and butterflies of having fewer nectar plants for forage and fewer safe roost sites available as stopovers.

More than 70 percent of all birds, bats, and butterflies that migrate between the U.S. and Mexico travel routes bounded by the Continental Divide in the Sierra Madre Occidental and Rockies to the east and by the Colorado River/Sea of Cortes to the west (6). Despite earlier concerns that these migrants were being threatened by deforestation in the tropical and temperate forests (7), more thorough analyses suggest that both vertebrate and invertebrate migrants may undergo severe stress while in transit across arid areas of low productivity and high climatic variability (8, 5).

Consider, for example, the western populations of the rufous hummingbird (Selasphorus rufus), which move through coastal Sonora, Arizona, and Southern California. These tiny birds have been found in transit at such low body weights that they cannot continue their migration (8). Their weights were marginal for a number of reasons: loss of nectar resources due to competition from invasive plants, global warming and drought, and roosting/foraging habitat loss.

Other migratory pollinators showing local or regional declines include the Sonoran Desert populations of white-wing doves, coastal populations of lesser long-nosed bats, and those monarch butterflies (Danaus plexippus) that migrate to Michoacan, Mexico, from west of the Rio Grande watershed (2, 5).

Whether generated by climatic variability, herbicides, pesticides, or land conversion, en route stresses on migratory pollinators can have devastating effects. Pollinators require a tight synchrony between their migration and the peak nectar availability of flowering plants along their “nectar corridor” (3).

Restoring Ecological Connectivity
The best way to ensure adequate connectivity in regional reserve networks is to better manage intervening private lands in a manner consistent with the needs of migratory wildlife. Yet, in their current state, many private lands are the weak links in the migratory chain. Restoring the ecological connectivity of these lands will require stronger stewardship collaborations among public agencies, private land owners, and rural ejido collectives.

Dr. Exequiel Ezcurra (formerly the lead scientist for Mexico’s Instituto Nacional de Ecologia) echoed this point in a keynote address remembered for its political wisdom as well as its excellent science. In May 1998, at the international conference on the Conservation of Migratory Pollinators and Their Corridors held at the Arizona-Sonora Desert Museum, he pointed to the increasing political difficulties of establishing additional large protected areas in Mexico and the U.S. He predicted that few new reserves are likely to be established in northwest Mexico. As such, restoring ecological connectivity through private lands between federally protected areas will be critical to binational regional conservation efforts.

One success story of public-private collaboration is the remarkable recovery of riparian corridors using treated sewage effluent along binational riverbeds in the Arizona-Sonora borderlands. Because of its southeast-northwest alignment contiguous to north- south running rivers in Sonora, the Rio Santa Cruz is part of a 400km corridor of intermittent streams and associated riparian vegetation stretching across some of the driest portions of arid North America. This corridor has unprecedented importance to binational wildlife movements, given that only 10 percent of the historic riparian vegetation remains along the rivers and streams of southern Arizona (6).

In 1980, the Nogales International Waste Treatment Plant began to augment historically diminishing instream flow with treated effluent. The plant now provides continuous flow and replenishment of the shallow aquifer below the flood plain for 40 km north of Nogales, Sonora. By 1992, along a stretch of floodplain that had formerly lost most of its gallery forests, newly established stands of cottonwoods, willows, and mesquites covered more than 45 percent of the Upper Rio Santa Cruz flood plain (6). Additional restoration efforts using treated sewage effluent along the Rio Santa Cruz are currently being implemented by Pima County as part of its Sonoran Desert Protection Plan. This is an ambitious multi-species Habitat Conservation Plan, which has strict guidelines for targeting and managing these waters to regenerate floodplain habitats for several species of conservation concern, including migratory pollinators.

Mark Larkin began his restoration efforts where the Nogales Treatment Plant left off. He seasonally reduced or increased grazing in different patches to create healthy stands capable of long-term growth on the available water budget of treated effluent. With his consent, we began attempts at active restoration of pollinator habitat in 1997. These efforts included wildflower plantings, artificial nest placements, and other pollinator population enhancement techniques described in detail elsewhere (2, 6).

In addition to twenty-five species of migratory pollinators benefiting from these passive and active restoration efforts, we have documented some 322 species of invertebrate pollinators now in residence on Tubac Farms. There were potential seasonal increases in other species as well. Within the last decade, ornithologists have recorded nearly two hundred birds in the watershed’s headwaters. While it was not possible to assess population changes for so many species, certain neotropical migrants show clear signs of recovery.

Within the Upper Rio Santa Cruz corridor, we can now point to the success of a decade of efforts on Tubac Farms. This private land experiment demonstrates the utility of promoting pollinators’ “nectar trails” as a means to maintain healthy corridors across private lands between protected areas. These efforts not only benefit the pollinators themselves but also provide habitat for numerous other species, including habitat-modifying keystone plants and animals, frugivores, and perhaps even carnivores. The ecological restoration and subsequent management shifts at Tubac Farms convince us of the value of collaborating with a range of private land owners to enhance the ecological functionality of an entire corridor.

Conclusion

In addition to documenting their ecological role in linking landscapes, plants, and animal populations, our emphasis on pollinators as a means to define corridors has had several practical political advantages in promoting land stewardship. Efforts to define, promote, and restore corridors to ensure pollination services, for example, will likely meet with far more acceptance among farmers and ranchers than advocating for corridors to increase the movements of carnivores. Moreover, government initiatives such as the USDA’s Wildlife Habitat Incentives Program (WHIP) and the Sustainable Agriculture Research and Education (SARE) Program can subsidize pollinator habitat restoration as a means to benefit both crop yield stability and wildlife in general. Rather than emphasizing carnivores in the already contentious debates among farmers, ranchers, biologists, and conservation activists, we might do well to find common ground in our shared interest in maintaining pollinator services and then evaluate the extent to which this strategy indirectly provides more corridor habitat for carnivores.

Even if stepping-stone corridors suited to migratory pollinators do not function for all carnivores, it is hard to imagine how existing data on carnivore movements will be sufficient—in and of themselves—to empirically confirm where natural corridors still function and where they need to be restored. In contrast, there are thousands of migratory bird, bat, and butterfly observations and flowering plant records available to empirically define nectar trails. DNA and isotope tracking techniques can determine empirically which faunal samples taken at different stopovers are from the same breeding populations. Observations made by volunteer naturalists (compiled on the Arizona-Sonora Desert Museum web site: www.desertmuseum.org) may help locate other corridor segments that are in need of protection and/or restoration. Tracking the precise binational movements of carnivores—and establishing where corridors function for them—will take much longer. Nevertheless, the Migratory Pollinators Project, the Wildlands Project, the Sky Island Alliance, and Northern Arizona University are now beginning to compare the efficacy of using carnivores versus pollinators in the design of corridors to capture maximum levels of biodiversity possible in the U.S./Mexico borderlands.

Gary Paul Nabhan is Director of the Center for Sustainable Environments at Northern Arizona University.

Literature Cited

1. Nabhan G.P. et al. 1998. The potential consequences of pollinator declines on the conservation of biodiversity and stability of food crop yields. Conservation Biology 12(1):8-17.

2. Buchmann, S. and G.P. Nabhan. 1997. The Forgotten Pollinators. Island Press, Washington D.C.

3. Fleming, T.W. 2000. Pollination of columnar cacti in the Sonoran Desert. American Scientist 88(5):432-439.

4. Lavee, D. and U. N. Safriel. 1989. The dilemma of cross-desert migrants: stopover or skip a small oasis? Journal of Arid Environments 17:69-81

5. Pyle, R.M. 1998. Chasing the Monarchs. Houghton-Mifflin, New York.

6. Nabhan, G. P. and J. Donovan. 2000. Nectar trails for pollinators: Designing corridors for conservation. Arizona-Sonora Desert Museum Technical Monograph 4, Tucson Arizona.

7. Terborgh, J.W. 1989. Where Have All The Songbirds Gone? Princeton University Press, Oxford.

8. Calder, W.A.1997. Hummingbirds in Rocky Mountain meadows. In K. Able, ed. A Gathering of Angels: The Ecology and Conservation of Migratory Birds. Cornell University Press, Ithaca. p. 149-168.

Acknowledgments

We thank the many researchers who contributed to the Migratory Pollinators Project and its precursor, the Forgotten Pollinators Campaign, especially staff at the Arizona-Sonora Desert Museum, the Programa para la Conservacion de los Murciélagos Migratorios founded by UNAM and Bat Conservation International, and the University of Arizona. We particularly thank the following team members for sharing their data: Jim Donovan, Stephen Buchmann, Ty Fitzmorris, Karen Krebbs, Pete Siminski, Steve Hopp, Ginny Dalton, Keith Labnow, and Laurian Escalanti. Mark Larkin hosted us at Tubac Farms, and Steve Walker facilitated collaboration in the region. Christine DeCarlo assisted with manuscript preparation. Support was provided by the Turner Foundation, the Wallace Global Fund, the Turner Endangered Species Fund, the Wallace Research Foundation, the C.S. Fund, the W. Alton Jones Foundation, the Roy Chapman Andrews Fund, and Border 21.

Suggested Readings

Buchmann, S. and G.P. Nabhan. 1997. The Forgotten Pollinators. Island Press, Washington D.C.

Soulé, M.E. & J. Terborgh (eds.). 1999. Continental Conservation: Scientific Foundations of Regional Reserve Networks. Island Press, Washington D.C.

Winter 2001 (Vol. 2, No. 1)

People love living on lakes, but they may be damaging the ecosystems they treasure. Compared to lakes with no residential development, lakes with many houses along the shoreline have bluegill sunfish that grow more slowly and are smaller for their age, according to new research presented in the May/June issue of Ecosystems.

This work is the first study of how lakeshore development affects the growth rates of fish in those lakes and was done by Daniel Schindler of the University of Washington in Seattle and co-authors. To determine if lakeshore development affects the growth of fish, Schindler and his colleagues surveyed bluegills (Lepomis macrochirus, a fish common throughout the contiguous U.S.) in 14 lakes in northern Wisconsin and the Upper Peninsula of Michigan. Three of the lakes had no development, seven had low-density residential development, and four had high-density residential development (nearly all of the shoreline was developed).

Residential development in watersheds can increase the nutrient levels in lakes and can decrease the number of dead trees in nearshore waters. Dead trees are critical fish habitat, providing foraging grounds and refuge from predators. The researchers had noted that people remove trees from lakes, presumably to improve both the view of and access to the lake.

Schindler and his colleagues found that as lakeshore residential development increased, bluegill growth rates decreased. The average annual bluegill growth rate in heavily developed lakes was only about 40% of that in undeveloped lakes. The researchers also found that as residential development increased, bluegill populations had increased numbers of older fish, suggesting that the adverse effects of lakeshore development might be greater for young fish than for adults.

These findings suggest that extensive lakeshore development can reduce a lake’s capacity to maintain fish populations. Schindler and his colleagues urge lake and land managers to develop proactive plans that protect a lake’s nearshore and riparian habitats. Schindler’s co-authors are Sean Geib of the University of Wisconsin in Madison and Monica Williams of the University of Maryland-Eastern Shore in Princess Anne.

Further Information:
Schindler, D.E., S.I. Geib, and M.R. Williams. 2000. Patterns of fish growth along a residential development gradient in north temperate lakes. Ecosystems 3:229-237.

Daniel E. Schindler

Dept. of Zoology, University of Washington, Box 351800
Seattle, WA 98195-1800 USA email hidden; JavaScript is required

Winter 2001 (Vol. 2, No. 1)

Prevention is a concept that does not come naturally to most Americans. We are a culture that places full faith in our ability to emerge victorious from battle no matter what the odds, and the American approach to danger and uncertainty has always been to go in guns blazing and sort things out after the smoke clears. It should therefore come as no surprise that one or another government agency or conservation organization is always declaring a “war on weeds.” Though few would say it in so many words, Americans think prevention is for wimps.

But the war on invasive species is a war that can only get worse. International commerce and travel are growing exponentially, and trade is destroying natural barriers between ecosystems just as fast as it removes barriers to the movement of goods. In a world whose motto has become “No limits,” the cost of this loss of ecological isolation is growing daily. The time has come to admit that there are some battles that are better prevented than fought. With a little luck, we might learn some ecological humility before the casualties become too great.

Preventing Accidental Introductions
Preventing accidental introduction of pests is something everyone can agree on in theory. There is a general social consensus that certain kinds organisms — mostly plant and animal pathogens, insect pests, and obvious weeds — are not welcome. Where disagreement begins is on how high to raise the bar. How much benefit is society willing to forgo, and how much regulation will people put up with in order to avoid accidental pest introductions? Thoughtful evaluation of these choices demands a clear understanding of what constitutes high- and low-risk activities, a realistic assessment of the power of inspection systems to erect protective barriers, and a creative approach to developing proactive programs to identify and reduce risk.

High- and Low-Risk Importation Patterns

The level of risk imposed by a given type of importation depends more than anything on the ecological relationship between the source and destination of the product being moved. Importation of untreated larch logs from Siberia to western North America, for example, would be inherently risky in that ecological similarities between the two regions make it highly likely that pests that arrive on imported logs would thrive at the expense of native tree species. In contrast, mahogany logs imported to New York would pose little threat to the local forest ecosystem, even if they occasionally brought their bark beetles or borers with them. These species would have no local hosts and would be unable to survive.

However, the relative degree of risk of a given pattern of importation depends not only on the nature of such relationships, but also on the volume and character of the cargo itself. Overall, importation patterns that pose a high risk of pest introduction involve commodities that are moved between regions with similar climates and plants, commodities that are moved in large quantities on a regular basis, and commodities that readily conceal pests. Conversely, the risk of accidental pest introduction is relatively lower for commodities that are imported from regions with less rigorous climates, commodities that are moved to areas where similar plants are not present to serve as hosts, and commodities that are moved in small quantities. Any estimate of the degree of risk of a given action is based on an educated but ultimately subjective assessment of the net effects of all the above factors.

Government efforts to reduce risks often entail placing conditions on importation that regulate how and where different kinds of imported goods from different points of origin must be handled. Importations that pose a high risk of accidental introduction are generally regulated more heavily than those that are considered to pose a low risk, but even with importation patterns that are essentially guaranteed to carry pests, regulation is much more commonly used than outright prohibition. For instance, one common stipulation of an importation permit is that a given item may be imported to certain parts of the country but not to others. But relying on such limited permission is a poor strategy for controlling the risk of invasion, for national borders are the only practical line of defense. Ultimately, the only reasonable way to handle high-risk importations is to prohibit them entirely.

Inspections as a Tool for Detecting Invaders

To slow the rate of uninvited nonnative species introductions, most countries inspect incoming materials in an effort to detect stowaway organisms. This usually consists of asking travelers if they are carrying such high-risk items as fruit, seeds, or live plants, items that generally are either potential pests themselves or potential hosts of insects or pathogens. Inspectors are also responsible for reviewing the documentation and checking the contents of commercial shipments of goods, be they tankers full of wood chips or planeloads of roses.

Given the large and increasing volume of food, ornamental plants, wooden packing materials, and nursery stock shipped internationally each year, inspectors typically are limited to spot checks of a few shipments. Inspections are therefore filters — not barriers — and they often miss nonnative invaders at either of two levels. First, the fact that only a tiny fraction of shipments are actually inspected provides ample opportunity for organisms to be missed by simple non-inspection. Although inspectors focus their efforts on high-risk shipments (making actual inspection efficiency somewhat higher), much is missed. Second, even for shipments actually checked by an inspector, some kinds of organisms can easily be overlooked, especially if they are hidden — wood-boring insects in packing material, for example — or invisible, such as pathogens that have not yet caused visible symptoms. The chestnut blight, for example, entered the country on apparently healthy Asian chestnut (Castanea mollissima) seedlings. Even if these trees had been inspected, detection would have been impossible without the help of skilled plant pathologists and without enough time to take and culture samples before shipments were released. Similarly, the Asian longhorned beetles (Anoplophora glabi-pennis) that are now killing maples in the New York and Chicago regions invaded as beetle larvae inside wooden crates used to ship manufactured goods from China. Such internal or microscopic organisms are extremely difficult to spot, even with concerted effort.

Inspection is effective only if the nature and volume of the cargo that inspectors are charged to examine are constrained by sensible policies regarding what can and cannot be brought into the country. Relying on inspection as a primary barrier instead of a final check is akin to trying to filter a river of muddy water with a handkerchief. It will fail.

Active Prevention of Species Movement

For species known to be dangerous or pathways very likely to promote movement of unwanted species, governments can create proactive programs to reduce the rate of introduction. Some states have their own proactive efforts against particularly threatening species. For example, Hawai ‘i has mobilized a major effort to prevent invasion of the brown tree snake (Boiga irregularis), an Asian predator that would drive many of its remaining native bird species to extinction. Hawaii’s approach has two major components: snake-proofing the airports on Guam and inspecting cargo from Guam as it arrives in Hawai’i. The fewer snakes there are at airports and in warehouses on Guam, the less likely it is that they will stow away in crates or other goods leaving Guam. And in Hawai ‘i, a combination of fences, snake-detecting dog teams, and protocols for responding to snake sightings provide a means of detecting snakes should they arrive on airplanes from Guam. In the longer run, though, the overall density of snakes on Guam must be reduced — by introduction of pathogens or other means — so that Guam’s threat as a source of infestation to the rest of the northern Pacific islands is permanently lowered. Anything else is simply a holding action.

Another form of active prevention has been applied to the movement of aquatic species in the ballast water of cargo ships. The bilges of large ocean vessels are floating aquaria, picking up a variety of species (mostly plankton and other invertebrates) in the coastal waters of one continent and then discharging them in another when ballast water is pumped out at the port of destination. This route of entry became a concern in North America in the early 1990s following the discovery that zebra mussels (Dreissena polymorpha) had been accidentally introduced into the Great Lakes via ballast water. The high cost of the zebra mussel invasion in North America prompted the passage of a law requiring ships to exchange ballast water in the high seas or treat ballast water with chemicals. These and other regulations, while not yet robust, have the potential to change what was a high-risk pattern of international trade into a relatively low-risk one.

Invited Species That Become Invasive
Though the techniques for prevention differ, the same fundamental logic that applies to reducing the likelihood of accidental introductions also applies to minimizing the risk of unintended impacts of deliberately imported species. Keeping out accidental stowaways focuses on the composition and size of the regulatory wall erected; evaluating species for deliberate importation concerns when it is acceptable to open the gates. Unfortunately, the same kind of misunderstanding of the nature of biological risk that allows for one accidental introduction after another also prevents the creation of a comprehensive system of evaluation for proposed introductions. Until there is a fundamental shift in public understanding of risk that allows for a much more vigorous and proactive approach to both wall-building and gatekeeping, prevention efforts will only delay invasions, not prevent them.

There are two approaches commonly in use for the evaluation of proposed introductions. “Dirtylists” identify species that are known or presumed to be harmful and prohibit their importation and release. This approach to prevention is grounded in the assumption that species proposed for importation are innocent until proven guilty and is the principal approach used in the United States. “Cleanlists” consist of species for which the preponderance of evidence indicates relatively low risk of invasiveness or harm and allows for their importation without review. Australia and New Zealand have pioneered this approach to prevention. The track record of this second approach is too short to draw conclusions yet about its practical effectiveness. However, there is great promise in the fact that cleanlists substitute a presumption of guilt for the presumption of innocence that underlies the dirtylist approach.

Dirtylists and Their Shortcomings

Whether a dirtylist is at all useful depends largely on the length of the list and the thoroughness of the efforts to determine if it is reasonably complete. At its simplest, a dirtylist is merely a roster of a country’s past mistakes — that is, of introductions already made and therefore largely irrelevant to prevention. If species are prohibited only after they have invaded and caused damage, the only benefit of compiling such lists is the chance they offer to slow the spread of new invaders to as-yet-uninvaded areas within the same country.

A more useful approach would be one in which the listing agency actively seeks information about species in advance of importation requests for the purpose of better recognizing species that should be dirtylisted, perhaps because they are pests elsewhere or have features — such as tolerance of a wide range of habitat conditions—that suggest they might readily become pests. Australia is presently trying proactive review of South African plants to dirtylist species likely to be invasive in Australia before they are requested for import.

In a regulatory climate dominated by economics, though, any particular strongly proactive dirtylisting attempts are likely to run into political difficulties. Importers whose income would be affected if the range of importable species were reduced are likely to object vigorously to any such attempt to dirtylist anything but obviously damaging species. They are likely to argue, often persuasively, that they are suffering undue economic harm and that there is no clear proof that any particular suspicious species is risky enough to merit exclusion. Within a standard framework of risk analysis, the importers’ arguments are sound because the risk that any particular species will actually become invasive is quite small. Unless there is nearly incontrovertible evidence of likely damage, few risky species will be dirtylisted based on this approach to risk evaluation.

Herein lies the fundamental limitation of dirtylists. Excluded species are the special category, not the default classification. This means that people have a right to bring in any new species they want, unless its importation has been proven so obviously detrimental that it warrants prohibition. The presumption of innocence and the focus on individual rights rather than collective risk define the dirtylist approach and place such large constraints on its use as to render it of limited value. It is the direct equivalent of how pesticides were regulated before passage in 1947 of the original pesticide control act (FIFRA), which shifted the burden of proof from government to industry. Before 1947, government health officials had to prove on a case-by-case basis that a particular pesticide residue was dangerous. After the passage of FIFRA, pesticide companies wishing to market a pesticide had to prove the product was safe. Though the system certainly has its defects, its orientation at least allows for the possibility of improvement.

Cleanlists: A Proactive Approach

If one takes the view that people do not have any intrinsic right to import nonnative species, then the burden should be on importers to show that the species to be brought in will not cause harm. Since the ability to identify invasive species in advance is limited and the consequences of being wrong are great, such a conservative approach — one that makes prohibition the default and permission the exception — is the only sensible strategy. This shifting of the burden of proof is the key to effective prevention.

Such a presumption of possible harm is the principle underlying the cleanlist approach. All nonnative species are assumed to be potentially damaging, and only those that appear unlikely to become invasive are allowed to be imported. But even use of cleanlists may present difficulties. For small groups of relatively well known species like birds, mammals, and other vertebrates, cleanlisting is probably technically feasible. For large groups like insects and plants, it is not. There are so many species in each of these groups (many of them unknown) that to even make a list of all species — let alone gauge the potential invasiveness of each — simply is not possible.

However, the power of the cleanlist approach is not so much in the lists of permitted species that are generated as in the fact that anything not yet reviewed is presumed to be unsafe. The practical consequence of this approach would be to eliminate frivolous species importations, for only those with real social, economic, or ecological benefit would be worth the time and expense required to demonstrate noninvasiveness. Introductions would still happen, but only after careful consideration.

Current U.S. Policy Regarding Nonnative Species
The inability of the U.S. government to formulate a coherent national policy on the importation of nonnative species (accidental or deliberate) derives largely from the fact that people have very different feelings about different kinds of organisms. As a consequence, the process of evaluation for each kind of species begins with a different set of assumptions about the relative threat a given class of organisms presents. These assumptions have their origins more in cultural history than in ecological science, but their influence over policy is profound. The United States’ agricultural roots condition people to see most plants (especially beautiful or edible ones) as beneficial and most insects that eat plants as suspicious at best. It also predisposes us to look favorably upon most mammals, birds, and fish, especially game species. Most everything else simply fails to register. But invasive species come in many varieties, and effective prevention demands a levelheaded and ecologically based approach to evaluating the potential benefit and harm of each proposed introduction.

For the most part, nonnative plants are assumed to be innocent and beneficial — and therefore noninvasive. Importation is forbidden only for a tiny handful of plants (under 200 species, most of which are crop weeds or parasitic plants). While invasiveness in natural areas has long been poorly reflected in the species chosen for dirtylisting, the recent inclusion of several invaders of natural areas (such as the shrub Mimosa pigra, the Australian paperbark tree Melaleuca quinquenervia, and the invasive marine seaweed (Caulerpa taxifolia) suggests the beginning of an expansion — albeit a slow and tentative one — of the scope of prohibitions.

Importation of any herbivorous insect or plant pathogen is forbidden unless specifically authorized; any species that attacks plants is viewed as a potential threat to agriculture. (This policy applies to both accidentally introduced plant pests and those proposed for introduction as biological control agents.) Plant importation is recognized as the major route of such invasions, and as a consequence, laws were passed early in the twentieth century that require inspection and quarantine of imported plants. It is important to note, however, that inspections are only for insects and diseases; in general, the plants themselves are not an object of scrutiny.

The blanket prohibition on introduction of plant feeders is not without holes. For example, butterfly houses routinely import herbivorous insects, often with little or no review. The fact that butterfly importations are generally permitted highlights the non-ecological foundation of importation policies; for species that do not “look” threatening are more likely to be let in regardless of their actual impacts. Whether butterfly houses will be a source of species invasions is not yet certain, as importation of butterflies for such purposes is a relatively new phenomenon. The likelihood is that in the long term, they will.

Importation of non-herbivorous insect species for use as pets, biological control agents, or other commercial purposes is generally viewed favorably by the federal government. Biological control agents for insect pests were for many years viewed as inherently safe, wholly beneficial, and contributing to increased public safety by reducing the use of pesticides on crops. In more recent years, several cases of negative impacts of biological control agents on nontarget species have been identified, and both the scientific community and the public at large have begun to evaluate biocontrol introductions more carefully. Other avenues of introduction of non-native insects are still subject to little or no scrutiny. For example, imported species of cockroaches and spiders are now commonly available in pet shops. Given that most such species do not eat live plants, most are not regulated by federal plant protection acts. Some states (such as Florida) have recently passed legislation banning their sale, but the ease with which such species can be shipped across state lines significantly limits the effectiveness of regulation at anything but the federal level.

Importation of “wildlife” (roughly, terrestrial vertebrates) poses two problems, only one of which is covered by current laws in the United States. First, nonnative wildlife can vector diseases that might affect native wildlife, a threat addressed in comprehensive quarantine laws. However, current laws do not address the threat of invasion of natural areas by imported wildlife species themselves. Importers must show only that the imported species is not a disease vector and that it is not a rare or threatened species in its area of origin. (Some states do prohibit such introductions on grounds of invasion potential, but again, state laws are of limited effectiveness.) Wild elephants roaming the west Texas plains seems far-fetched, but wild emus in Georgia appear to be a reality following the collapse of the emu-rearing craze. Whether they will prove damaging is not yet known, but the fact is that their release has introduced a major new animal to the ecosystem.

A series of disasters in the nation’s waters have heightened governmental awareness of the impacts of introduced species on aquatic environments and resources. In particular, the economic impacts of zebra mussels run into the billions of dollars, and zebra mussels threaten dozens of species of native mussels with extinction. Other aquatic species threaten to degrade (or have already degraded) the productivity of shell and fin fisheries in Chesapeake Bay. These and other problems spurred the passage of a federal law requiring ships entering the Great Lakes to treat their ballast water chemically or exchange ballast water on the high seas, as stated earlier. The next logical step is to extend this requirement to all U.S. ports and eventually to all shipping by means of an international treaty.

Other aspects of the aquatic species threat, however, remain unaddressed. Fish reared commercially (for food or for sale to hobbyists) may themselves become unwanted invaders of native habitats. The blue tilapia (Oreochromis aureues), for example, has invaded the habitat of threatened native fish in parts of the western United States. However, because fish farming is an agricultural enterprise, fish species under cultivation are considered a valuable resource, and the threats they pose to native ecosystems are largely ignored.

Developing Better Policies for Prevention
The development of a better system of prevention is not just a technical matter of framing more comprehensive legislation. The effectiveness of even the most comprehensive set of new laws will be constrained by the degree to which they deal with two key issues: free trade and accountability. Integrating protection measures into trade policy and creating a funding mechanism for mitigation of damage serve as a platform on which sound prevention measures can be developed.

The Dilemma of Free Trade

Laws prohibiting the entry of a given type of product on grounds of prevention of invasions have at times been attacked as protectionist measures in disguise. Under current world treaties on trade, such practices are subject to challenge by the country whose products are excluded. For example, when the United States prohibited the use of packing crates made of untreated wood for shipping of commercial goods from China to America in 1998, the Chinese government objected on the grounds that such measures constituted an unfair barrier to trade. Though China eventually dropped its objections once it became clear that untreated wood crates had been the source of the Asian longhorned beetle invasion, this kind of conflict will only become more common under the strongly pro-trade regulatory regime that now dominates at the international level.

Efforts to limit trade to prevent pest invasion and protect local biodiversity will increasingly have to be defended in World Trade Organization dispute panels against opposing interests whose economic concerns would be hurt by such restrictions. How will the still-uncertain ecological and economic costs of potential invasions be judged against the easily quantifiable economic costs if permission to import a specific good is denied? What is missing is a broad body of knowledge of the social and economic consequences of nonnative species invasions. Since loss of the amenities that natural systems provide is often incremental, few people realize just how enormous a weight pests already present impose on economic use and enjoyment of the natural world. A recent study by David Pimentel of Cornell University attempted to quantify the negative economic impacts of invaders and estimated that invasive nonnative species currently cause about $137 billion in damage annually in the United States alone. Many more studies of this kind are needed because, until prevention speaks the language of economics and well as ecology, it will consistently take a back seat to free trade.

A System of Accountability

When invasions happen — and they will continue to occur even under a well-designed prevention program — who should pay to mitigate their effects, whose economic impacts alone can run into millions or even billions of dollars? Under current law, it would be difficult if not impossible to assess blame and impose damages. Unfortunately, society operates on the assumption that unless specific violations of importation regulations occur, invasions are no one’s fault. Even if it was willful negligence that led to the introduction of a new pest, the offending party is not responsible for anything more than the fines associated with such violations. A shipping company could be fined for failing to flush bilges before entering coastal waters, but it could not be held responsible for the costs imposed on society by any new invaders that it happens to carry in its ballast water.

In any case, it is often impossible to link most invasions to the persons or corporations responsible. One alternative would be to take a cue from the insurance industry and levy a fee on international shipments in proportion to their potential to cause biotic invasions. All groups benefiting from trade in nonnative species (or types of cargo that can carry them) would be required to pay into a mitigation fund based on the volume and nature of the cargo they carry. Money raised would then be held in reserve to allow rapid funding of efforts to eradicate new invaders or develop biological control programs for pests if they are only detected after eradication is no longer possible. Such a system would require that businesses and individuals trading in risky organisms take collective responsibility for resolving the problems that arise from their activities. Such a pooled system would sidestep the obvious defense made by such groups that only a small percentage of nonnative species become damaging and would instead recognize the even more compelling truth that these few species, while not numerous, affect large areas and impose huge economic and ecological costs.

Placing “Filters” Between Ecosystems and Trade

Even though outright prohibition of all vectors of species movement is not feasible, a few well-chosen measures would serve to reduce the number of new introductions per year. Proposed changes in federal laws or regulations regarding prevention of introductions might logically be organized around a series of “filters” designed to protect native ecosystems from damaging invasion. Since the legal context of species importations and trade regulation in general is constantly changing, the following points — or filters — provide a brief indication of possible new legislation and regulations needed without proposing specific, detailed pieces of legislation.

1. Encourage the preferential use of local native species from local seed sources. An executive order requiring that all federal agencies use only native species for landscaping, revegetation, and other activities, unless there is a compelling reason to use a nonnative species; and requiring the same of all state and local units of government and private organizations that receive federal funds.

2. Encourage the preferential use of nonnative species that, based on experience, appear to be highly unlikely to become invasive. A law prohibiting the deliberate introduction of any new nonnative species without review, and either providing federal funding for evaluation of requests to import species or mandating payments by importers (or both).

3. Develop robust inspection services to detect and exclude unwanted stowaway organisms. Revised regulations giving postal and customs inspectors the authority and the funding to inspect both domestic and international mail and cargo suspected of carrying prohibited species; new laws that impose substantial penalties for the interstate or international shipment of prohibited species without permission.

4. Identify high-risk species and/or vectors of introduction. Increased funding for APHIS, the federal agency charged with these matters; new legislation giving APHIS an express mandate to prohibit permanently and totally the importation of any species whose life history suggests the potential for invasiveness, and to control high-risk pathways of introduction.

5. Create a remediation fund that would be available for rapid response to new invasions. A law imposing a fee on all economic activities that serve as vectors of species introduction; new regulations and interagency agreements that create a system of detection and response to new invasions using funding generated by the new fee.

The Federal Executive Order on Invasive Species
The process of developing a series of protective filters between invasive species and native ecosystems has already begun. On February 3, 1999, President Clinton took a significant step toward creating a comprehensive nonnative species policy with Executive Order 13112. This order is binding on all federal agencies and requires them to:

1. Identify any actions they may be taking that promote harmful nonnative species invasions.

2. Prevent the introduction of harmful invasive species.

3. Monitor harmful invasive species (in their lands or areas of responsibility) and take rapid, appropriate action to reduce spread of such species.

4. Restore native species and habitats affected by invasive species.

5. Conduct research on invasive species and develop new technologies for their suppression.

6. Promote public education on the impacts of invasive species.

More broadly, the executive order requires creation of an Invasive Species Council to serve as an advisory committee at the highest levels of the federal government. The job of the council (now underway) is to oversee the implementation and coordination of the executive order within and among the relevant federal agencies. The council encourages planning at multiple levels of government, provides guidance to agencies on how to prevent or control damage from invasive species, facilitates the development of an information network among federal agencies for monitoring and documentation, establishes a coordinated set of databases on nonnative species, and prepares a National Invasive Species Management Plan (see www.invasivespecies.gov for more information). An important feature of this plan will be to review existing and prospective approaches and legal authorities for preventing the introduction and spread of invasive species — that is, to determine if new laws or regulations are needed and, if so, in which areas.

The Council and Plan offer an unprecedented opportunity to create a coordinated and comprehensive system for preventing and managing nonnative species problems. If the federal agencies responsible for working with the Council and implementing the Plan follow through on the intent of the executive order, the United States may be able to slow the rate of new introductions significantly. This may be the best chance we will ever have to institute effective policies of prevention while there are still invasions to prevent.

Suggested Reading

Quammen, D. 1996. The Song of the Dodo. Scribner, New York.

Bright, C. and L. Starke. 1998. Life Out of Bounds: Bioinvasion in a Borderless World. W.W. Norton and Company, New York.

Harmful non-indigenous species in the United States. 1993. Office of Technology Assessment, U.S. Government Printing Office, Washington, D.C.

Williamson, M. 1996. Biological Invasions. Chapman and Hall, London.

Web Sites:
National Invasive Species Council

www.invasivespecies.gov

Official site of the interagency effort to implement the Executive Order. A draft management plan is available for download.

Invaders Database System

invader.dbs.umt.edu

A compendium of publications, invasion histories, and pest descriptions. Also offers an alert service and a database searchable by region and topic. Focuses largely on plants.

American Lands Alliance’s Invasive Species Page

www.americanlands.org/forestweb/invasive.htm

Information on current national invasive species policy issues.

Alien Plant Working Group of the Plant Conservation Alliance

www.nps.gov/plants/alien/

Nationwide lists of invaders, factsheets, and links to other sites.

Animal and Plant Health Inspection Service

www.aphis.usda.gov

Information on all major regulatory issues. Special reports on “hot topics.”

About the Author:

Jason Van Driesche is a graduate student in the Institute for Environmental Studies and the Department of Urban and Regional Planning at the University of Wisconsin-Madison.

Roy Van Driesche teaches and researches biological control at the University of Massachusetts-Amherst, and is co-author of the textbook Biological Control (Chapman and Hall, 1996). He is Jason’s father.

This article was excerpted from the recent book, Nature Out of Place: Biological Invasions in the Global Age by Jason Van Driesche and Roy Van Driesche (Island Press, Fall 2000).

Thanks to conservation efforts, U.S. deer densities are the highest they have been in 100 years. But the downside is that too many deer may be bad for forest birds, according to new research in the August issue of Conservation Biology. This is the first study showing that deer can drive at-risk bird species out of forests. The link is that deer determine which types of plants grow in the understory, which in turn determine the types of birds that live there.

“Large hooved mammals are landscape engineers, and deer are the dominant herbivores in the eastern United States,” say William McShea and John Rappole of the Smithsonian Institution’s Conservation and Research Center in Front Royal, Virginia, who collaborated on this study.

In 1991, McShea and Rappole fenced white-tailed deer out of eight 10-acre plots in protected forests in both the Conservation and Research Center and Shenandoah National Park. They assessed the abundance and types of understory vegetation in the plots in 1994 and 1997 and estimated the abundance and types of breeding birds in the plots by mist-netting yearly from 1990 through 1998.

The results showed that excluding deer shifted the understory vegetation from grasses to forbs (non-grass herbaceous plants) to Rubus species (the blackberry family) to woody shrubs. While bird diversity was constant through these shifts, the relative abundance of the 25 species that commonly nested in these forests varied considerably: 10 species increased and four declined.

Those that declined were resident birds (such as the tufted titmouse, blue jay, and northern cardinal) that are stable or increasing in the U.S. Those that increased were migratory species (such as the hooded warbler and ovenbird) that are more at risk according to factors that include range-wide abundance and population trends.

While it is clear that managing deer can benefit at-risk bird species in eastern forests, McShea and Rappole recommend basing management on the density of understory vegetation rather than on the density of the deer themselves. This is because deer at a given density can result in different vegetation densities, depending on such factors as soil wetness and richness. Specifically, the researchers suggest monitoring orchids and lilies, which are common throughout the eastern U.S. and sensitive to changes in deer densities.

Further Information:

McShea, W.J. and J.H. Rappole. 2000. Managing the abundance and diversity of breeding bird populations through manipulation of deer populations. Conservation Biology 14(4):1161-1170.

William McShea (540-635-6563) email hidden; JavaScript is required

John Rappole (540-635-6537) email hidden; JavaScript is required

Something was rotten in the state of amphibia. Chatting casually in the hallways at the first World Conference of Herpetology in 1989, scientists shared story after story of mysterious declines and disappearances among various species of frogs.

Once, for example, a certain ridge in the Monteverde Cloud Forest of Costa Rica became a riot of psychedelic, flame-orange color for 5 to 10 days each year as the golden toad (Bufo periglenes) congregated to mate. But scientists at the conference said that in 1988, only 10 golden toads were seen, and just a single male showed up in 1989. Other attendees said they had witnessed similarly rapid and dramatic declines among frogs in the rain forests of eastern Australia and the highlands of eastern Brazil.

And this was no common tragedy. Amphibians weren’t just disappearing from places where their habitat was being destroyed or where they were exposed to pollution. They were also vanishing from forest reserves and other pristine habitats far from human disturbance.

No one at the conference presented scientific evidence that amphibians were on the decline, but the sheer number of anecdotes shared in the hallways was worrisome. Could it be true that amphibian species were winking out, one by one, from every corner of the globe? If so, why? Was it something we humans were doing—something less obvious than, say, clearing forests but just as deadly?

Ten years later, we are well on our way to answering some of these questions. The reality of amphibian declines is well accepted in the scientific community and widely reported in the press. Moreover, scientists are making strides in identifying some causes of the declines, most notably with the identification of a new species of fungus that appears to be killing frogs from Australia to Arizona.

A major player in research on disappearing amphibians over the past decade has been the Declining Amphibian Populations Task Force (DAPTF), a volunteer network of more than 3,000 scientists in over 90 countries that operates under the umbrella of the Species Survival Commission (SSC) of the IUCN/World Conservation Union. DAPTF has gathered and disseminated information, sponsored symposia and conferences, and funded research on declining amphibian populations.

In the final analysis, however, DAPTF’s biggest contribution may not be to establish the reality or even the cause of amphibian disappearances but to show that you don’t need a deep purse or a complicated, bureaucratic organization to tackle big scientific problems.

DAPTF was formed in late 1990, after a workshop on declining amphibians sponsored by the U.S. National Research Council was held in Irvine, California. (The workshop, in turn, was a response to concern raised at the World Conference of Herpetology.) There, more than 40 herpetologists from all over the world presented hard data demonstrating the recent declines of many amphibian species.

They also found, however, that information was missing from whole regions of the world—Africa for example—so it was difficult to demonstrate that the declines were a global problem. Moreover, since amphibian populations tend to fluctuate from year to year and because long-term data were scarce, scientists couldn’t be sure whether the declines were part of a normal pattern or real cause for concern.

What the herpetology world needed was a coordinated, global effort to address these issues—to gather background data on amphibians worldwide, to determine which species were declining, and to investigate possible causes.

“I conceived the idea of DAPTF at the Irvine conference,” says David Wake of the University of California at Berkeley, who was one of the conference organizers. “I talked to various people and simply assembled an international group of people who might be interested.” The problem of amphibian declines first came to light in an informal way, and DAPTF developed in a similar fashion, driven by the passion of scientists and the networks between them.

“I was an experienced administrator and simply put together DAPTF in as simple a way as possible,” says Wake. In general, the organization seems to be structured and run according to this straightforward, common-sense approach.

George Rabb, Chair of the SSC, suggested the relationship with SSC. “The situation was beyond the scope of professional disciplinary organizations. . .and had major conservation implications,” he explains. In addition, “two other SSC Specialist Groups with herpetological subjects (on marine turtles and on crocodilians) were making great impacts in conservation,” and the amphibian task force could benefit from their model.

DAPTF headquarters was first established at the Center for Analysis of Environmental Change at Oregon State University in Corvallis and later transferred to The Open University in Milton Keynes, United Kingdom. Forming alliances with established institutions not only decreases the resources required to run DAPTF but also gives the group a broader reach. The SSC, for example, has access to more than 7,000 scientists in 179 countries.

Like the hero of the classic hard-boiled detective story, who typically keeps a spare office with a desk, a chair, and a bare light bulb, DAPTF has adopted a low-overhead strategy to tackle the scientific mystery of amphibian declines. “We have always been exceedingly simple and ‘lean,’ with minimal staff,” says Wake. “We have gone a long way on volunteers and now have been successful in obtaining funding from diverse organizations, none of it ‘big’ funding.”

The real work of DAPTF is done by individual herpetologists organized into Working Groups, which are based either on geography (e.g., Central United States, South Asia) or around specific scientific issues (e.g., determining whether global climate change is involved in amphibian declines). “Our network of Working Groups appears to be unique in that there is no counterpart for any other taxon,” says Tim Halliday, International Director of DAPTF. Each Working Group obtains its own funding and determines its own structure and leadership.

Unlike the hard-boiled detective, who of course is famous for working alone, DAPTF can function only if its members are tightly connected and well informed about each other’s activities and results. This coordinating role is the main purpose of DAPTF headquarters, which consists of an International Director and International Coordinator. An International Board of Directors, currently with 10 members representing six countries, sets research priorities and determines fundraising strategies.

“The trouble with science is that it’s a very slow process,” says Halliday. “In my view the main purpose of DAPTF is to make science work a little faster.” DAPTF headquarters does this in two ways: by encouraging communication and by promoting research on amphibian declines.

To encourage communication among its members, DAPTF publishes a newsletter, Froglog, six times a year. Froglog began as an informal compendium of reports on declining amphibians even before DAPTF was organized. According to Wake, another herpetologist had come up with the name Froglog a couple of years earlier. “I liked the name and used it myself to assemble information—mostly anecdotes—from people around the world and kept it on my office computer.”

Today, the scope of Froglog, which is published both electronically and in hard copy, is somewhat broader. Recent issues have included articles on the status of amphibians in Vietnam, Cuba, Bangladesh, Sri Lanka, New Zealand, Panama, and other countries; a description of an Ecuadorean program to address the issue of declining amphibians; reports on collaborative programs in amphibian conservation, one involving scientists in the United States, Canada, and Mexico, the other in Belize, Guatemala, and Mexico; discussions of the global threats to amphibians including nitrates, ozone depletion, and disease; requests for information, research proposals, and donations; and announcements of upcoming conferences.

Production of the newsletter is the job of Halliday and International Coordinator John Wilkinson, both based at The Open University. The process is typically informal. Many scientists simply send in articles unsolicited; the editors weed out the ones containing results they think should be published in a peer-reviewed format. In addition, says Halliday, “I solicit quite a lot of articles, typically when I hear and talk to people at meetings.” He considers the newsletter, widely praised in the herpetological community, one of the Task Force’s main successes.

Another way of promoting communication is by bringing people together face to face. DAPTF has organized a symposium at every World Conference of Herpetology (except the first). The Task Force also recently helped organize a series of workshops in Mexico, Panama, and Ecuador that involved 88 people from 13 countries all together. “Probably we make the biggest difference in the developing world,” says Halliday, where scientists have access to fewer resources and less institutional support.

To promote research on amphibian declines, DAPTF gives Seed Grants, onetime awards of $500 to $2,000 on topics identified by the Board of Directors, such as the effects of global climate change and UV-B radiation on amphibians.

“Our Seed Grant program has been a huge success,” says Halliday. So far, 44 grants totaling $92,000 have been given to researchers all over the world. “On average, each grant awarded has yielded one or two publications in recognized journals, and on average, the grant holder has turned each $1 given by DAPTF into $20 from other sources.”

The Seed Grant that Halliday calls “probably the biggest individual success” of the program helped Southern Illinois University researcher Karen Lips study frogs in Panama’s Reserva Forestal Fortuna. In 1996-97, Lips found several streams with no frogs at all and others that had lost half their frog species since she’d surveyed the area a few years before. She also found a number of dead and dying frogs, a rare sight because such frogs tend to be snapped up quickly by predators and scavengers. The dying frogs trembled or convulsed, and many of the dead frogs seemed “frozen” in their nightly calling positions, as if they had died very quickly. All of this suggested that a great many frogs at Fortuna were dying rapidly; this, in turn, was evidence of a disease epidemic.

Similar evidence was being uncovered on the east coast of Australia, where 14 species of frogs had declined sharply or had become extinct since the 1970s. The declines had happened very rapidly over the course of just a few years for each species. Moreover, scientists had traced the geographic spread of the die-offs from population to population, a directional pattern typical of an epidemic.

Later in 1997, DAPTF helped organize a workshop at the University of Illinois, where researchers established that both the Australian and the Panamanian frogs had been killed by disease—a fungus later dubbed Batrachochytrium dendrobatidis. Related species of fungi, known collectively as chytrids, are important pathogens of algae, insects, and other groups but had never before been known to infect vertebrates. B. dendrobatidis apparently feeds off the keratin of amphibians’ skin.

The fungus was soon confirmed as the cause of more than a dozen frog die-offs in eastern Australia and 10 in Panama. It has also been implicated in recent frog population declines in southwest Australia, Costa Rica, Spain, Africa, and Arizona, and California. Scientists have even found evidence, from preserved specimens, that it may have been involved in die-offs in the U.S. and Australia during the 1970s and 1980s (some of the very die-offs that first raised the alarm about declining amphibians). Many herpetologists now believe that the chytrid is the major factor behind amphibian declines in Australia and the Americas.

No one thinks the fungus explains all amphibian declines. And most herpetologists agree that local habitat destruction is the biggest threat facing amphibians today. Still, the news was exciting because this was the first time scientists had found evidence of a causal factor that could explain amphibian declines as a global phenomenon.

Halliday is reluctant to suggest DAPTF deserves credit for this success. “I have no doubt that if DAPTF did not exist, much of the research into declining amphibian populations of recent years would have been done anyway,” he says. “DAPTF does provide an international focus for all this research, but the value of that is hard to assess.” All along, DAPTF has been more interested in encouraging and guiding research than in controlling or dictating it, and that makes the group’s impact and success difficult to evaluate.

DAPTF’s non-traditional structure and approach has raised other challenges. “In the rather odd context of scientific evaluation that currently exists in the U.S. and the U.K., running something like DAPTF is not regarded as ‘real research’,” says Halliday. Those who coordinate the network may face pressure because they “cannot enrich the research reputations of our institutions by publishing in the high impact journals or by pulling in big grants from the usual sources.”

Nevertheless, DAPTF is forging ahead with an approach that challenges traditional academic boundaries and assumptions. A new initiative, headed by ecologist Jim Collins of Arizona State University, involves 24 scientists from diverse fields who will explore the role of host-pathogen relationships in amphibian declines. DAPTF helped secure funding from the U.S. National Science Foundation for the program. It is hoped that this interdisciplinary approach will answer some of the remaining questions about the chytrid fungus and help scientists understand why the disease has emerged so suddenly and so virulently in widely scattered locations. It may even help scientists and managers take a long-hoped-for next step: figuring out how to stop or prevent amphibians from disappearing.

Sarah DeWeerdt is a freelance writer in Seattle, Washington.

For more information:

DAPTF web site www.open.ac.uk/daptf/

Amphibia Web elib.cs.berkeley.edu/aw

Amphibian Diseases www.jcu.edu.au/school/phtm/PHTM/frogs/ampdis.htm