Pollution Ecology
Old studies offer new insights into pollution’s effects on ecosystems
Fewer. Smaller. And things could get worse in a warmer climate. Those are just a few of the conclusions reached by a massive new study that tries to tease out the fundamental effects that industrial air pollution has on organisms and ecosystems – and some recommendations for better focusing future research.
For decades, ecologists have debated whether they could make general, universal predictions about how pollutants affect ecosystems. Nearly 25 years ago, for example, pioneering ecologist Eugene Odum predicted that pollution would typically make ecosystems less diverse by killing off sensitive species, and hit predatory species hardest.
To see if they could confirm some of those predictions of “pollution ecology,” more than a decade ago two researchers — Mikhail V. Kozlov and Elena L. Zvereva of the University of Turku in Finland – began the time-consuming task of assembling a massive database of studies. Some were 50 years old, and all offered data on how pollution from a particular source – such as a cement or steel mill – affected a particular species or ecological community. Over the years, they’ve mined their data trove to explore how air pollution affected the diversity, abundance, and performance of soil microfungi, bryophytes (land plants without circulatory systems) vascular plants and terrestrial arthropods, such as insects, spiders and centipedes. Although some general patterns emerged from these studies, it wasn’t clear if they could be broadly applied.
To find out, Kozlova and Zvereva decided to go all in: They combined their studies into a single mass of data, and then used powerful statistical tools to conduct a “meta-anlaysis” that compared how everything from individual organisms to entire communities responded to an array of pollutants in very different climates. In all, they used data from about 500 studies published between 1953 and 2009. They included data collected near 206 point polluters in 36 countries, including aluminum smelters, cement plants, steel mills and chemical facilities. Most were in Russia (61), Poland (23), Canada (17) and the United States (17 ). In general, the studies examined how pollution affected organisms at different levels in the food web, including producers, consumers and decomposers. The authors also examined how a wide range of factors – such as soil pH, air temperatures, and pollution concentrations and duration – altered impacts.
Their results, set out in the journal Environmental Pollution, are both highly nuanced and painfully clear. Although different groups of organisms reacted differently to specific kinds of pollution, “the overall effects… on individual performance, abundance and diversity were negative,” the authors report. They confirmed Odum’s prediction that pollution decreases species diversity, for instance, and a related prediction that surviving organisms tend to have smaller body sizes. They also saw clear evidence that surviving organisms become “pollution tolerant” over time, suggesting that “evolutionary adaptation to the impact of pollution is a general phenomenon.” Other past predictions, however, weren’t borne out: They found that pollution didn’t necessarily hit predatory species hardest, for instance.
The statistical tour-de-force also revealed a complex but troubling link between pollution and climate. Warmer temperatures appeared to enhance the effects of pollution on producers and decomposers, for instance, but reduced the impact on primary and secondary consumers. And the authors warn that complex interactions between global warming, pollution, plants and pests could produce some “ecological surprises” – such as greater damage from pests that respond differently to pollution than their target plants.
Finally, the authors say the study highlights some weaknesses in current studies focused on pollution ecology. One problem, they note, is that journals often don’t require researchers to include data that could be useful for similar large-scale analyses. And they say some classic approaches, such comparing the growth of a single plant species in polluted and unpolluted areas “can be seen as a poor use of research money,” and should be re-tooled to take a broader view of whole communities and ecosystems. – David Malakoff | November 17, 2010
Source: Kozlov, M., & Zvereva, E. (2010). A second life for old data: Global patterns in pollution ecology revealed from published observational studies. Environmental Pollution DOI: 10.1016/j.envpol.2010.10.028
Image © Srećko Petrović | Dreamstime.com
