“Birds in the United States are not only declining, but they are declining faster, especially in areas with intensive agriculture, according to new research. Overall drops in bird population, measured from 1987 to 2021, were sharpest in warm and warming areas, suggesting that climate change may play a role”
“The study, published on Thursday in the journal Science, shows only correlation with intensive agriculture and temperature, not causation. It does not factor in other circumstances that may be affecting birds along migratory routes or while they are overwintering”
“it adds to an ever more robust body of evidence that birds — one of the best measured families of animals on Earth, and a sentinel for the health of other species — are not OK”
“In 2019, Dr. Marra and a team of scientists published landmark findings that the number of birds in the United States and Canada had fallen by 2.9 billion, or 29 percent, since 1970”
“Thursday’s study relied on one of the same data sources, the North American Breeding Bird Survey, a monitoring project led in part by the United States Geological Survey”
“In 1987, the team found, each route had 2,034 birds on average. By 2017, that average had decreased by 304 birds per route, or 15 percent. The steepest losses were seen in Florida, Texas, Louisiana and Arizona. Generally, they correlated with warm places and, to a lesser degree, with places that saw rising temperatures over the past 30 years”
“The team decided to add further analysis, using statistical modeling to look for associations. Among 20 metrics, they looked at fertilizer use, pesticide use and area of cropland. “What we found is that any metric of agricultural intensity was always the best predictor of acceleration of the decline.””
““We want to be very careful here,” said Marta Jarzyna, one of the authors and a professor at Ohio State who specializes in macroecology. “It’s very difficult to really get the mechanism of change with a large-scale, continental-scale correlative study such as ours.””
“Many scientists believe that trouble in the insect world, where declines are much harder to quantify, is creating trouble for birds. Most terrestrial bird species in North America depend on insects at some point in their life cycles, often when they are young”