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By Robert Lalasz
Air pollutants such as mercury, ozone and acid rain are harming every ecosystem type in the eastern United States, according to a groundbreaking new report co-authored by The Nature Conservancy and the Cary Institute of Ecosystem Studies.
But what is to be done? Is the Western United States still safe? And is air pollution combining with other stressors such as climate change to bring nature to a tipping point?
For answers, nature.org talked with two co-authors of the report — the Cary Institute's Gary Lovett and the Conservancy's Tim Tear.
Nature.org: What was the study's most significant finding?
Lovett & Tear: That air pollution is stressing all of our major ecosystem types. It's compromising each one in different ways — but air pollution is ultimately harming the biological diversity these ecosystem types support and the services they provide to society. And those impacts are profound and disturbing.
Nature.org: Has air pollution been hitting nature harder recently, or are we just seeing the cumulative effects of 100 years of degradation? Or both?
Lovett & Tear: In the Northeast, overall air pollution has actually been getting better since the passage of the 1990 Clean Air Act. But because of the legacy of air pollution impacts over the past century, it is difficult to assess if any of the 1990 regulations go far enough to result in ecosystem recovery.
We need two things to improve our current situation. First, we need air pollution regulations based on the needs of these ecosystems, in addition to the standards set for human health. Second, we need a more comprehensive and integrated monitoring system to help us better understand the responses of these ecosystems to air pollution.
Nature.org: How far behind are we in establishing a comprehensive monitoring system for air pollution deposition? What's needed?
Lovett & Tear: There's already been a lot of good work that we can and must build on.
As the report points out, there are already six networks in place measuring different aspects of atmospheric deposition and water quality. These networks must be maintained — and that's no small issue, as their funding is constantly at risk.
But there are serious gaps in what we monitor — for instance, our forest monitoring is sparse, and we don’t monitor soil or most kinds of non-game wildlife. The current monitoring efforts are fragmented and underfunded.
We need a more integrated and comprehensive monitoring network (a) to evaluate and refine critical loads for sulfur, nitrogen and mercury, and (b) to evaluate the ecological responses to this new regulation over time.
Nature.org: So these air pollutants are damaging nature. Does that damage impact humans, too?
Lovett & Tear: Another great question. The national air quality standards address the direct health impacts of air pollution on people — mostly, the medical problems caused by breathing the polluted air.
But humans are also affected by the degradation of the ecosystems and the services they provide. For example, air pollution has made our streams and rivers less healthy, which has resulted in significant impacts to our inland fisheries.
Mercury is so high in most of these states that there are restrictions on the number of freshwater fish you can catch and eat. In the Adirondacks — a place that is particularly sensitive to air pollution impacts — acidification has resulted in the loss of many fish species from our lakes, and many lakes are now actually fishless.
In addition, acidification and ground-level ozone affect our forests. They do not grow as fast, and are more susceptible to disease and insect attacks — which reduces timber production.
Similarly, nitrogen deposited high up in the mountains or far away in the headwaters of small streams ultimately ends up in our estuaries, where algal blooms and eutrophication reduce the productivity of our coastal fisheries.
And finally, ground-level ozone is altering one of the most fundamental ecological processes — photosynthesis — that has contributed to additional stresses on our forests, has reduced agricultural production, and recently was associated with the decline of honey bees and pollination.
Nature.org: How might these stressors be combining with stressors such as climate change? Are we close to a disastrous tipping point for some ecosystems?
Lovett & Tear: We know very little about how these multiple stressors actually interact. Climate change, land-use change, non-native species invasions — all are large stressors that make it difficult to predict how ecosystems will actually respond.
Yet as we state in the report, this lack of knowledge should not be an excuse for inaction. Lowering atmospheric deposition will reduce the likelihood of damage to natural ecosystems — no matter what other stressors are present.
Nature.org: You've said that, just because the report is about the eastern United States, the rest of the country isn't safe. What impacts from air pollution are other parts of the country seeing?
Lovett & Tear: This problem is not at all restricted to the Northeast or Mid-Atlantic States.
In the United States, critical loads for nitrogen are being used in Rocky Mountain National Park, where negative impacts to aquatic resources have been documented. Mercury has also been found to reduce the reproductive success of the clapper rail in California, the great egret in Florida and the snowy egret in Nevada. Ground-level ozone has damaged pine forests in California.
Air pollution is extensive in its impacts — it's spread throughout the developed world and is increasing in the developing world. For example, the first effects of acid rain were noticed in Europe a century and a half ago, and air pollution is mentioned as consistently as a problem in China for the upcoming Olympics.
The eastern United States just has a wealth of information that makes it possible to do a more comprehensive study that helps us paint — for the first time — a more accurate picture of the overall impacts that air pollution is having on our planet.
Robert Lalasz is senior editorial manager for nature.org
Nature picture credits (top to bottom, left to right): Photo © Eric Middelkoop/BigStockPhoto (smokestack); Jerry and Marcy Monkman (salamander)
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