Subscribe to the new Harvest newsletter, for our latest reporting on agriculture and the environment, behind-the-scenes exclusives, and more.
A new study finds bird populations are declining at a faster pace in areas with a lot of agriculture, especially in the Midwest.
The loss of bird populations has been documented since the 1970s. A landmark study from the Cornell Lab of Ornithology published in 2019 found the North American bird population is down by 2.9 billion breeding adults across geographical regions since then.
The recent study at Ohio State University found that across North America, more than 120 bird species are experiencing decline, and of those, more than half are experiencing accelerated decline.
Researchers focused on geographic areas where they saw faster declines in bird populations, including in the Midwest, California and Mid-Atlantic states. They then focused on potential causes and found a strong link between accelerated bird decline and areas with a lot of agriculture.
“The data we had access to were the amount of pesticides used, the amount of fertilizer used and the amount of croplands,” said François Leroy, the lead author and a post-doctoral student at Ohio State University.
Prior studies have found habitat loss, declines in insect populations and the climate crisis to be key contributors to bird decline. The new research found that agricultural practices are speeding up the already occurring decline, Leroy said.
“You could have a decline and just the decline per se was related to the temperature, where the acceleration of the decline was related to agricultural practices,” he said.
The study was published in Science in February.
Mike Ward is a professor studying bird behavior and ecology at the University of Illinois Urbana-Champaign and read the study. He said these findings – although new – were not surprising.
“Some changes in agricultural practices have led to reductions in habitat and likely food availability,” he said.
Increased fertilizer use and a lack of native plants around fields may be behind the faster decline of bird populations, he said.
“The pressure’s on farmers to get as much yield as possible,” he said, “and that easily results in getting rid of hedgerows, getting rid of other pieces of habitats and then using various chemicals or fertilizers and such to try to maximize yields.”
Creating more land that’s habitable for birds would help populations, Ward said. He points to a program from the U.S. Department of Agriculture that pays farmers to convert highly erodible and environmentally sensitive acreage to vegetative cover.
Bird decline has grave consequences for broader environmental health. Birds regulate insect populations, spread plant seeds and are an important element on the food chain that other animals rely on.
Ward said he knows farmers are concerned about the environment, including bird loss.
“They really want to do things, and then we’ve got to think strategically about these small things they can do,” he said.
Andrew Stillman, an applied quantitative ecologist with the Cornell Lab of Ornithology, said the study’s findings are very important. Now, more research needs to be done to find solutions, he said.
“It’s time to understand the mechanisms behind these changes using more localized studies that go above and beyond the correlations shown in this study to show which aspects of agricultural intensity are impacting birds the most and what can we do about it,” he said.
Stillman thinks it is still possible to stop the decline before irreparable damage is done.
“I also think that there’s good news here, because we’ve seen that it’s possible to reverse those declines," he said. "Think about birds like bald eagles or peregrine falcons or even some waterfowl species. There are a lot of success stories that we’ve seen over the last 50 years, and that tells us that recovery of bird populations is possible.”
But if nothing is done, bird populations will continue to decline at increasingly faster rates, Levoy said.
“If we continue to use intensive agriculture, this acceleration should continue,” he said.
He hopes the study will start conversations, especially in the agricultural community.
“The most important [thing] here is to start a dialogue with the farmers, because we need to keep in mind that farmers are the real field experts,” Levoy said. “They are the ones who are walking everyday in the fields. I think they’d have a lot to say about what we’ve observed in the data.”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
