A rainbow greets geese on the Pacific Flyway in the Sacramento Valley
Every year, millions of waterbirds migrating from Alaska to Patagonia take a break from that epic journey to rest, eat and breed in a stretch of wetlands spanning six Western states called the Great Basin.
A warming climate has made that migration more challenging by altering how mountain snowmelt flows into the network of lakes and rivers stretching from the Sierra Nevada to the Rockies, according to a new study based on 25 years of climate, weather and avian population data.
Researchers found that “climate warming has significantly reduced the amount and shifted seasonality of water flowing into wetlands” throughout the region, altering habitat for migratory birds, according to the study in Scientific Reports.
It suggests the trend will continue with warming weather causing snow to melt earlier and shifting peak flows. That could benefit some birds, but threaten others.
“We looked at birds that breed in the Great Basin. If they don’t find water at their breeding sites, specifically fresh water, they won’t be able to survive. It’s a serious situation,” Susan Haig, the report’s lead author and a professor at Oregon State University, said in a news release.
The Great Basin stretches across Nevada, Utah, Wyoming, Idaho, Oregon and California, and is frequented by all manner of waterbirds, including geese, herons, ducks and cranes.
More than 2 million waterbirds pass through southern Oregon and northeastern California along the Pacific Flyway, stopping at the San Luis National Wildlife Refuge Complex in the San Joaquin Valley, the Sacramento National Wildlife Refuge Complex, Mono Lake and the Salton Sea, the study says.
Some birds, like the black-necked stilt and the sandhill crane, which breed early in the season, have thrived in the warming climate, said Mohammad Safeeq, a hydrologist with the Sierra Nevada Research Institute and an adjunct professor at UC Merced.
But others suffer. That includes the killdeer, the Wilson’s snipe, the black tern, and the western and Clark’s grebe.
“We have looked at 14 species and among eight open-water and shoreline foraging species that have undergone significant population declines, five were negatively associated with temperature increases,” Safeeq said in an email interview.
The report also found that drier summers lead to saltier wetlands, and that’s a major problem for birds that are unaccustomed to a saline environment.
Meanwhile, shore bird populations have dropped 70 percent since 1973 ,according to prior research cited in the report. Those birds often breed in Great Basin waterways, such as Mono Lake in eastern California.
Safeeq said it’s unclear how long or whether certain avian species will disappear from the Great Basin.
“It’s hard to put a timeline. Nature can surprise you,” he said.
He said bird populations probably will continue to decline unless government agencies create a regional approach to preserving their habitat.
The researcher said efforts by The Nature Conservancy and the Natural Resources Conservation Service to create “popup wetlands” — when farmland is flooded to create temporary wetlands — is an example of what can be done at the local scale, he said it’s “not enough to combat the habitat loss as shown in the paper.”
“We need to change the pace and scale of habitat restoration along the (North American) Pacific Flyway and work towards a long-term strategy that is focused on multiple benefits,” Safeeq said.