WASHINGTON— A new study finds that billions fewer birds are flying through North America compared to a decade ago and populations are shrinking faster than ever, primarily because of high-intensity agriculture and warming temperatures.

The findings come as a congressional panel meets today to consider weakening a key bird-protection law.

The peer-reviewed study, published in Science, noted that previous studies have shown that North America’s birds are disappearing at shocking rates. But the new research found that hotspots of accelerating declines are associated with regions with intensive agricultural practices (high cropland area, high fertilizer use or high pesticide use) and warming temperatures.

“This heartbreaking study shows that almost every group of birds is doing poorly because of reckless agricultural practices and human-caused climate change,” said Tara Zuardo, a senior campaigner at the Center for Biological Diversity. “Extinction starts with declines like these, and birds are often the indicators that our environment is too toxic to support other life. These findings are a powerful rebuke to Republicans on Capitol Hill who’re trying to gut the Migratory Bird Treaty Act.”

Today a Republican-led House committee is holding a hearing as part of a plan to undermine the Migratory Bird Treaty Act. The hearing will address the future of the Act and the protection of migratory birds from harm and death, in part due to large-scale industrial activity.

The Trump administration claims that the Act only covers intentional killing of migratory birds. But in 2020 a federal court disagreed, noting that the Act makes it unlawful to kill birds “by any means whatever or in any manner.”

North America’s bird populations have plunged by almost 3 billion birds over the past five decades, according a landmark study — a loss of nearly one in four birds since 1970.