Dec. 2, 2020 – Successful efforts over the past 50 years to reduce ozone pollution to protect humans have had another benefit. The loss of 1.5 billion birds has likely been averted, according to a study conducted for the past 15 years by scientists from Cornell University and the University of Oregon.

The study was published on Nov. 24, 2020 in The Proceedings of the National Academy of Sciences and reported by the Cornell Lab of Ornithology.

A separate study reported last year by the Cornell Lab of Ornithology showed that North American bird populations have declined by nearly 3 billion birds since 1970.* If ozone pollution had not been reduced, it’s likely 1.5 billion more birds would have died, according to the new study.

Ozone (O3)
Ozone is a gas with three oxygen atoms (O3). Oxygen, the vital gas needed for human and animal respiration, has two oxygen atoms (O2). What a difference one oxygen atom makes!

There is a layer of ozone in the upper atmosphere that protects Earth from the Sun’s harmful ultraviolet (UV) rays. But if ozone is at ground-level, the gas is hazardous. The gas occurs in nature but is also produced by internal combustion engines and power plants. Efforts over the past 50 years have concentrated on reducing pollution from cars, trucks, and power plants.

In 1970, Congress passed the Clean Air Act (CCA) to regulate air pollutants.

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

Clean Air Act of 1970
According to the Environmental Protection Agency (EPA), Congress established the nation’s policy to regulate air pollutants in 1970 with the passage of the CCA. Major revisions to the law were made in 1977 and 1990.

The 1970 action was prompted by visible smog in cities and industrial centers. The 1977 and 1990 revisions (amendments) addressed specific concerns, including acid rain and damage to the ozone layer in Earth’s stratosphere.

The CCA requires the EPA to establish air quality standards for certain common and widespread pollutants. Quality standards exist today for six common pollutants: particulate matter (particle pollution), ozone (O3), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO) and lead (Pb).

States are required to adopt enforceable plans to achieve and maintain air quality meeting the air quality standards. State plans also must control emissions that drift across state lines and harm air quality in downwind states, according to the EPA.

Clean air saves birds
For the study on birds and air pollution, 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 counties in the United States over a span of 15 years.

Study results suggest that ozone pollution is most detrimental to the small migratory birds, such as sparrows, warblers, and finches. These small migratory birds make up 86 percent of all North American bird species that live on land.

Ozone pollution directly harms birds by damaging their respiratory system, and indirectly affects birds by harming their food sources, such as insects.
 
“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,” Amanda Rodewald, Cornell professor and study author, said in a press release. “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.”

*(Rosenberg et. al. Science, 2019).