An under-examined biodiversity crisis has been creeping across North America for decades, according to new research: the mass loss of birds.
Since 1970, the US and Canada have experienced a loss of nearly 3 billion birds across both native and introduced species, the study found. This amounts to a nearly 30 percent reduction in bird abundance in 50 years, the study says, indicating that lasting damage to the integrity of these ecosystems may happen if we don’t start taking action to prevent it.
In the paper, published on Thursday in the journal Science, researchers from a number of academic and non-profit institutions in North America wrote that this decline can be attributed to the compounding effects of human-caused obstacles, such as habitat loss, pesticide use, and climate change. Notably, 90 percent of the total losses were experienced by widespread songbirds such as sparrows, warblers, blackbirds, and finches.
"The key is that breeding birds are being lost—along with their future offspring,” Ken Rosenberg, the study's lead author and a senior scientist at the Cornell Lab of Ornithology and American Bird Conservancy, said in an email. “In a normal, stable situation, there would be an upsurge in bird populations in late summer after all the baby birds are hatched. A certain percentage will not make it to adulthood but others will, while some adult birds will also die. It ends up evening out and the population remains stable. But more breeding birds are being lost, so it’s not a stable situation and it results in a net loss of birds overall."
It's a stark reminder that even common species can hurtle towards extinction, such as the passenger pigeon in the past, the study notes. According to Michael Parr, study coauthor and president of American Bird Conservancy it's hard to know where the tipping point is for irreversible losses. Of the nearly 30 percent total loss of birds, roughly 25 percent were native species.
“People talk about tipping points,” Parr said. “It would be hard to know if we’d reached an ecological tipping point … but with 25 percent loss of [native species of] birds, it tells me that we are approaching that kind of a situation in some ecosystems.”
The researchers used a combination of population trajectories and population surveys spanning 50 years, as well as observations from a network of 143 weather radars from between 2007 and 2017. Though grassland and forest birds alike experienced a loss in total population across the board, wetland birds were a notable outlier. These birds actually experienced a modest rise in population during the studied timeframe, something the authors attribute to the positive effects of wetland conservation efforts.
The authors also stress that these losses will not just impact the ecosystems of these birds, but also the natural relationships that humans benefit from, including seed distribution, pollination and pest control.
“When there's a loss of abundance, the ecosystem loses enormous services and functions that were once served by the birds that were there,” coauthor Peter Marra, director of the Georgetown Environment Initiative at Georgetown University, said in an email. “[W]e also lose our natural history heritage. A heritage we have an ethical and moral responsibility to protect. I liken it to if we were to lose paintings by Picasso, Monet, Rembrandt or a Homer…. Except these birds have been thousands of years in the making.”
While these findings may look stark, Parr emphasized that these early results should be a call to action, not a reason for fear or inaction.
“This is where it brings the biodiversity crisis back to America’s backyard,” Parr told Motherboard. “So often it’s just pandas, orangutans, [or] elephants that seem like a long way away. [But] this is in our backyard, it’s affecting all of us.”
As for how to take action, Parr, Marra, and Rosenberg recommended action on both political and individual levels.
"[There] needs to be international cooperation that makes preserving nature a priority," Rosenberg said. "Birds don’t recognize political boundaries—migrating birds especially cross many countries and to protect them for their entire life cycle we need to address problems on breeding grounds, migratory routes, and wintering grounds as well as the crucial stopover habitats they use along the way."
To save the birds, they said, we need policies that advocate for the protection of public lands, fewer pesticides, and to support non-profit conservation organizations.