Billions of birds have vanished from North American skies over the past five decades, a new study has found — and scientists say it is a sign of a major ecological crisis.
The bird population in the United States and Canada has plummeted by nearly 3 billion birds, or 29 percent, since 1970, according to a sweeping study published Thursday in the journal “Science.”
The researchers say the drop points to a “widespread ecological crisis” likely fueled by several factors — including the destruction of bird habitats and the widespread use of pesticides — that are made worse by climate change.
“We expected to see continuing declines of threatened species,” Ken Rosenberg, a senior scientist at the Cornell Lab of Ornithology and American Bird Conservancy, said in a statement. “But for the first time, the results also showed pervasive losses among common birds across all habitats, including backyard birds.”
Some 90 percent of the 2.9 billion birds lost belong to just a dozen families including sparrows, finches, swallows and warblers, the study found. Those common species play key roles in North American ecosystems by dispersing seeds and keeping pests under control, scientists say.
The bird researchers analyzed how populations changed for 529 avian species in the U.S. and Canada over about five decades using bird-monitoring data and a network of 143 radar stations.
The findings are similar to drops in bird populations elsewhere in the world, researchers say.
But some waterfowl and raptors, such as the bald eagle, have recovered over the last half-century thanks to legislation and conservation investments, the study found.
The study underscores the need for public policy and societal changes aimed at reversing the recent population declines, the scientists say.
“What our birds need now is a historic, hemispheric effort that unites people and organizations with one common goal: bringing our birds back,” Adam Smith, a co-author of the study from Environment and Climate Change Canada, said in a statement.
The findings come amid growing concerns about humans killing off the world’s wildlife. More than 1 million plant and animal species across the globe are at risk of going extinct, according to a United Nations report released in May.