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.