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The Clean Air Act has saved as many as 1.5 billion birds

Researchers at Cornell University are describing how a federal program designed to reduce ozone pollution has saved the lives of millions of birds over the last four decades. According to the study, air quality improvements associated with the Clean Air Act have saved up to 1.5 billion birds, which is the equivalent of nearly 20 percent of all the birds present in the United States today. 

“Our research shows that the benefits of environmental regulation have likely been underestimated,” said study lead author Professor Ivan Rudik. “Reducing pollution has positive impacts in unexpected places and provides an additional policy lever for conservation efforts.”

While ozone in the upper atmosphere protects the Earth from harmful ultraviolet radiation, ground-level ozone is the primary pollutant in smog and can be very hazardous to human health. When it comes to birds, ozone pollution causes direct harm to their respiratory system, and causes indirect harm by damaging their food sources.

To investigate how lower levels of pollution may have influenced bird abundance, the researchers used computer models that combined bird observations from the Cornell Lab of Ornithology’s eBird program with ground-level pollution data. The team tracked monthly changes in bird abundance, air quality, and regulation status for more than 3,000 counties in the United States over a span of 15 years. 

The results of the analysis suggest that ozone pollution is most detrimental to small migratory birds like sparrows, warblers, and finches, which make up 86 percent of all North American landbird species. 

“Not only can ozone cause direct physical damage to birds, but it also can compromise plant health and reduce numbers of the insects that birds consume,” explained study co-author Professor Amanda Rodewald. “Not surprisingly, birds that cannot access high-quality habitat or food resources are less likely to survive or reproduce successfully. The good news here is that environmental policies intended to protect human health return important benefits for birds too.”

In a separate Cornell study conducted last year, researchers found that North American bird populations have declined by nearly three billion individuals since 1970. The new study reveals that without the ozone-reduction efforts of the Clean Air Act, approximately 1.5 billion birds may have been lost.

“This is the first large-scale evidence that ozone is associated with declines in bird abundance in the United States and that regulations intended to save human lives also bring significant conservation benefits to birds,” said study co-author Catherine Kling. “This work contributes to our ever increasing understanding of the connectedness of environmental health and human health.”

The research is published in the journal Proceedings of the National Academy of Sciences.

By Chrissy Sexton, Staff Writer

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