New research suggests that modern farming practices are not just reducing bird numbers, but are actively accelerating their decline across the continent. While environmentalists have long warned of a “silent spring,” a study published in the journal Science reveals that the pace of loss has quickened significantly over the last three decades, particularly in regions dominated by intensive agriculture.
In a study conducted by Ohio State University, researchers discovered that over 120 bird species are in decline, with more than half of those disappearing at an accelerating rate across North America.
“The data we had access to were the amount of pesticides used, the amount of fertilizer used and the amount of croplands,” François Leroy, the lead author and a post-doctoral student at Ohio State University, 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.”
Since 1970, North America has lost nearly 3 billion birds. However, the new data shows that for many species, the steepest drops have occurred since 1987. Researchers identified a clear “acceleration” in these losses, citing the heavy use of pesticides, fertilizers, and the expansion of massive monoculture croplands as the primary culprits.
“Some changes in agricultural practices have led to reductions in habitat and likely food availability,” he said. “The pressure’s on farmers to get as much yield as possible 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.”
The crisis is most acute for grassland birds, such as the eastern meadowlark and the bobolink. These species have seen their populations plummet by more than 50 percent as their natural habitats are converted into industrial-scale fields of corn and soy.
“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,” Leroy said.
Scientists point to a “triple threat” within the agricultural sector. First, the widespread use of neonicotinoids and other pesticides has decimated the insect populations that birds rely on for food. Second, the removal of hedgerows and woodlots to maximize tillable acreage has stripped birds of nesting sites and migratory stopovers. Finally, the timing of mechanical harvesting often coincides with nesting seasons, leading to the accidental destruction of entire generations of fledglings.
Andrew Stillman, an applied quantitative ecologist with the Cornell Lab of Ornithology, said there is still time 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,” Stillman 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.”
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