Birds and clean air

Black-capped chickadee in Olean.

While the federal Clean Air Act was enacted to protect humans from air pollution, it also has saved birds.

The cleaner air resulting from the pollution regulations has saved 1.5 billion birds, nearly 20% of all birdlife in the U.S. today, according to researchers at Cornell University and the University of Oregon.

“Our research shows that the benefits of environmental regulation have likely been underestimated,” said Ivan Rudik, a lead author and Ruth and William Morgan Assistant Professor at Cornell’s Dyson School of Applied Economics and Management.

“Reducing pollution has positive impacts in unexpected places and provides an additional policy lever for conservation efforts.”

To investigate the relationship between bird abundance and air pollution, the researchers used models that combined bird observations from the Cornell Lab of Ornithology’s eBird program with ground-level pollution data and existing regulations.

They tracked monthly changes in bird abundance, air quality and regulation status for 3,214 U.S. counties over a span of 15 years.

They focused on the NOx (nitrogen oxide) Budget Trading Program, which was implemented by the U.S. Environmental Protection Agency to protect human health by limiting summertime emissions of ozone precursors from large industrial sources.

Ozone is a gas that occurs in nature and is produced by human activities, including power plants and cars. A layer of ozone in the upper atmosphere protects the Earth from the harmful ultraviolet rays of the sun. But ground-level ozone is hazardous and is the main pollutant in smog.

The researchers found that ozone pollution is most detrimental to the small migratory birds, such as sparrows, warblers and finches, that make up 86% of all North American land-based 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 author Amanda Rodewald, Garvin Professor at the Cornell Department of Natural Resources and the Environment and director of the Center for Avian Population Studies at the Cornell Lab of Ornithology.

“Not surprisingly, birds that cannot access high-quality habitat or food resources are less likely to survive or reproduce successfully.”

She noted, “The good news here is that environmental policies intended to protect human health return important benefits for birds too.”

A separate Cornell Lab of Ornithology study last year showed that North American bird populations have declined by nearly 3 billion birds since 1970.

The new study shows that without the regulations and ozone-reduction efforts of the Clean Air Act, the loss of birdlife may have been 1.5 billion birds more.

“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 Catherine Kling, Tisch University Professor at the Cornell Dyson School of Applied Economics and Management and faculty director at Cornell’s Atkinson Center for Sustainability.

“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 Catherine Kling, Tisch University Professor at the Cornell Dyson School of Applied Economics and Management and faculty director at Cornell’s Atkinson Center for Sustainability.

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