Which shall live and which shall die? Conservation triage for birds

There’s a struggle at the core of wildlife conservation between our desire to help and our ability to help. It’s a mismatch between the seemingly unending flow of species from existence to extinction and the limited resources at our disposal for use in stopping that flow.

On the one hand, we could try to spread our resources across the board as evenly as possible and risk helping nobody. Everybody would agree that is not an optimal outcome. On the other hand, we could try to determine which species are most important to be saved, for whatever reasons, and preferentially allocate our time, effort, and money towards work with those species.

This isn’t a new idea. Battlefield medics have struggled with the tradeoff between maximal success and limited resources for quite some time, which is what led to the establishment of a triage system. Some folks are deemed untreatable, and are simply made comfortable while they creep towards death, while the doctors’ efforts are focused on those with the greatest chances for successful recovery.

As science writer Michelle Nijhuis wrote in Slate last year, wildlife conservation requires a triage system as well:

Environmentalists have long been wary of any sort of triage approach to species conservation, and understandably so. Explicit triage is, in a way, an admission of failure, an acknowledgement that we’ve fallen short of the Endangered Species Act’s goal of protecting all species without prejudice. And any such acknowledgement could well be exploited by traditional foes of conservation.

But some environmentalists now say the status quo is an even riskier path. “The way we’re doing it right now in the United States is the worst of all possible choices,” says Tim Male, a vice president at Defenders of Wildlife. “It essentially reflects completely ad hoc prioritization.” Politically controversial species attract more funding, as do those with symbolic value (think bald eagles) or furry, expressive faces (think lemurs and baby seals). “We live in a world of unconscious triage,” says Male.

New research in Current Biology tries to help move the conservation from implicit, unconscious triage to a more explicit mechanism, at least for the world’s 9,993 recognized bird species.

Some methods for targeting conservation efforts have focused on species that are particularly aesthetic or functional, or ones with the greatest chances of success, or the largest ranges. The researchers, led by Yale University biologist Walter Jetz, chose to focus on what they call “evolutionary distinctness” or ED. It’s a way to assess how evolutionarily unique a species is by comparing its genome with the genomes of its closest relatives. Those who are least related – or most different from – their closest phylogenetic relatives would be more evolutionarily distinct.

This may be a useful metric by which to mark birds for conservation efforts, because there is incredible diversity in ED: on average, bird species have 6 million years of ED, meaning that their evolutionary lineage has been unique to their species for that long, but the minimum is just 800 thousand years and the maximum is more than 70 million years. For comparison, our lineage diverged from chimpanzees 6 million years ago, and our species, Homo sapiens, first emerged some 200 thousand years ago.

In general, high-ED species diverged from their ancestors longer ago than low-ED species; that makes sense, since more time would have passed. The genomes of high-ED species have simply had more time to become more different.

The researchers discovered that the top ten percent of birds with high ED clustered in a few isolated geographic areas. What is interesting, however, is that areas of the world known for their high biodiversity do not necessarily contain more top ten percent ED species. That means that the world’s rarest birds are not necessarily receiving protection from efforts to preserve the world’s biodiversity hotspots.

Countries who are particularly well positioned to preserve the birds with the highest ED include Australia, Indonesia, Brazil, Peru, Madagascar, Argentina, and New Zealand. “These countries carry a special responsibility for conservation global avian evolutionary information,” Jetz writes.

bird uniqueness

Areas of the planet with the greatest proportion of high-ED birds indicated in red. Left, non-passerines; right, passerines.

How can the measurement of ED be used strategically for conservation efforts? Jetz and his colleagues do it by combining ED with the geographic range for that species. That’s because high-ED birds, which are genetically unique, are not necessarily geographically restricted. Those species that are geographically restricted naturally face greater risk from habitat destruction and segmentation, and climate change. To calculate “evolutionary distinctness rarity,” or EDR, the researchers divided a species’ ED by its geographic range. That results in a value expressed as “evolutionary distinctness per square kilometer.”

The species with the highest EDR is the Christmas Island frigatebird. Its has 22 million years of unique avian evolutionary history, but all that genomic information is restricted to a geographic range measuring 110 square kilometers.

On the other hand, species with larger ranges but higher EDs will also wind up scoring high in EDR, like the giant ibis and noisy scrubbird. By combining ED with geographic range, the conservationists can account for both variables in a sophisticated, empirically driven way.

Combining the data generated from this study with the IUCN Red List, the world’s rarest, most evolutionary unusual, most at-risk birds are: giant ibis, New Caledonian owlet-nightjar, California condor, kakapo, Bengal florican, forest owlet, Philippine eagle, Christmas Island frigatebird, Sumatran ground cuckoo, and the kagu.

Arne O. Mooers, a Simon Fraser University biologist who oversaw the study, said in a statement, “[We] found that if we prioritize threatened birds by their distinctness, we actually preserve very close to the maximum possible amount of evolution…This means our method can identify those species we cannot afford to lose and it can be used to preserve the information content represented by all species into the future. Both are major goals for conservation biology.” – Jason G. Goldman | 18 April 2014

Data: Download the Excel file to see the raw data by species here.

Source (open access): Jetz W., Thomas G.H., Joy J.B., Redding D.W., Hartmann K. & Mooers A.O. (2014). Global Distribution and Conservation of Evolutionary Distinctness in Birds., Current biology : CB, PMID:

Header image: Christmas Island Frigatebird, the world’s weirdest, rarest bird, via Shah Jahan/Wikimedia Commons. Additional images via Jetz et al./Current Biology.