The Clean Air Act saved 1.5 billion birds

US environmental regulations to protect humans from dirty air also save birds. This completes a new continent-wide study published today in The Proceedings of the National Academy of Sciences. The study’s authors found that improved air quality as part of a federal program to reduce ozone pollution may have prevented the loss of 1.5 billion birds over the past 40 years. That’s nearly 20 percent of the bird world in the United States today. The study was conducted by scientists from Cornell University and the University of Oregon.

“Our research shows that the benefits of environmental regulation have likely been underestimated,” says Ivan Rudik, lead author and assistant professor to Ruth and William Morgan at the Dyson School of Applied Economics and Management at Cornell. “Reducing pollution has positive effects in unexpected places and provides additional policy leverage for environmental efforts.”

Ozone is a gas that occurs naturally and is also generated by human activities, including power plants and cars. It can be good or bad. An ozone layer in the upper atmosphere protects the earth from the sun’s harmful ultraviolet rays. However, ground-level ozone is dangerous and the main pollutant in smog.

American Robin, copyright Glyn Sellors, from the Surfbirds Galleries

To examine the relationship between bird abundance and air pollution, the researchers used models that combined bird watching from the Cornell Lab of Ornithology’s eBird program with pollution data from the ground and existing regulations. They tracked monthly changes in bird life, air quality, and regulatory status for 3,214 US states over a period of 15 years. The team focused on the budget NOx (nitrogen oxides) trading program implemented by the U.S. Environmental Protection Agency to protect human health by limiting summer emissions of ozone precursors from large industrial sources.

Study results suggest that ozone pollution is most harmful to the small migratory birds (such as sparrows, warblers, and finches), which make up 86 percent of all North American land bird species. Ozone pollution directly harms birds by damaging their respiratory tract and indirectly affects birds by damaging their food sources.

“Not only can ozone directly damage birds physically, it can also affect plant health and reduce the number of insects that birds consume,” explains study author Amanda Rodewald, Garvin Professor in the Cornell Department of Natural Resources and the Environment and director of the center for Bird population studies at the Cornell Lab of Ornithology. “Not surprisingly, birds that do not have access to quality habitat or food are less likely to survive or reproduce successfully. The good news here is that environmental measures to protect human health have important benefits for birds too. “

Last year, a separate study by the Cornell Lab of Ornithology showed that North American bird populations have declined by nearly 3 billion birds since 1970 (Rosenberg et al. Science, 2019). This new study shows that without the regulations and ozone reduction efforts of the Clean Air Act, the loss of bird life could have been 1.5 billion more birds.

“This is the first large-scale evidence that ozone is linked to a decline in bird populations in the United States and that life-saving regulations also bring significant conservation benefits to birds,” said Catherine Kling, professor at Tisch University at Cornell Dyson School of Applied Economics and Management and Faculty Director at Cornell’s Atkinson Center for Sustainability. “This work contributes to our ever better understanding of the interconnectedness of environmental health and human health.”

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