Two-thirds of all North American birds could face extinction because of climate change if greenhouse gas emissions aren’t curbed, the National Audubon Society said in a sweeping report released Thursday.
And that’s likely to include birds in your own backyard.
For example, the ruffed grouse has been the Pennsylvania state bird since 1931 but faces a moderate threat of being forced out of almost two-thirds of the state’s forests because of climate change, the report states.
In fact, 41 to 80 species are listed as “climate vulnerable” in Pennsylvania, depending on whether temperatures rise 1.5 degrees Celsius (2.7 Fahrenheit) or 3 degrees C (5.4 F) by the end of this century, given the amount of greenhouse gases from fossil fuels that continue to be pumped into the atmosphere, the report states.
Those at greatest risk in the commonwealth include the brown thrasher, cerulean warbler, Eastern whip-poor-will, and field sparrow.
Birds in New Jersey and Delaware face similar impact.
“We are already seeing impact on birds from climate change,” said Brooke Bateman, senior climate scientist for the National Audubon Society.
Bateman noted that “birds are important indicator species, because if an ecosystem is broken for birds, it is or soon will be for people, too.” Bateman and David Yarnold, the society’s president, released the report.
“Survival by Degrees: 389 Bird Species on the Brink” found that two-thirds of North America’s birds are threatened with extinction because of climate change but that keeping global temperature rise to 1.5 C could reduce the projected loss dramatically. That’s the temperature rise targeted by the Intergovernmental Panel on Climate Change to reduce the risk of global change.
Achieving that goal would require significant effort, researchers wrote: “Science tells us that in order to limit warming to a rise of 1.5C (2.7 F), we must reduce greenhouse gas emissions 45% below 2010 levels by 2030 and reach net-zero carbon emissions by 2050.”
Audubon scientists looked at 604 North American species of birds using 140 million records and factored in climate and habitat conditions. The report states that climate change is occurring 20 times faster today than it has during any other period over the last two million years.
And birds, the report said, are an ideal indicator of the impact of climate change. Certain birds feed on certain insects, so fewer of those birds could mean a rise in insect-borne diseases, such as West Nile virus. Birds also play critical roles in pollination, forest generation, and seed dispersal, the report notes.
Compared with habitat loss and changes in land use, the authors concluded climate change will have the biggest impact on birds. Extreme spring heat and heavy rainfall, among other climate-related events, are a major contributor to why birds move around.
Birds in the Northeast stand to be affected especially. Pennsylvania is projected to see average temperatures during the warmest months increase by 6 degrees C (11 F) by the end of the century. And average annual precipitation is expected to increase 2.9 inches.
“Either way, a lot of birds would end up not being able to occupy Pennsylvania because the climate would become different from what they need to exist,” said Keith Russell, program manager of urban conservation for Audubon Pennsylvania. “They’ll have to find areas north of the state, like New York and Vermont.”
Russell, who works out of Philadelphia, said local bird counts already are showing change.
“We’re already seeing changes in the distributions of the birds in the Southeastern Pennsylvania area,” Russell said. “It’s similar in the forests of New Jersey and Delaware.”
For example, the annual Philadelphia Mid-Winter Bird Census has found certain birds becoming less common in the city. The rough-legged hawk, American tree sparrow, and evening grosbeak are all harder to find.
As birds lose their traditional habitats and move on or disappear, others are moving in, Russell said.
For example, the black vulture moved up from the South and began colonizing in Pennsylvania in the 1990s. It is now common in the state, he said.
Russell said duck migration patterns are changing, particularly those that dive in deep water for food. The water is not freezing as early as it has in past decades, so the ducks can stick around longer. Species that once migrated south in October are staying until December.
In New Jersey, 58 out of 167 species are vulnerable because of the way summers are changing, the Audubon Society found. Sea-level rise is also a factor.
Species facing the biggest threat in the Garden State include the song sparrow, cackling goose, American black duck, Eastern whip-poor-will, and brown thrasher.
The National Audubon Society report comes on the heels of other recent unfavorable reports on bird populations.
Officials at the New Jersey Conservation Foundation pointed to a study last month in the journal Science that found the bird population in North America has shrunk by nearly three billion in the last 50 years, meaning there are 25% fewer birds alive today in the United States and Canada than there were in 1970.
“I see lots of backyard birds like cardinals and robins, but I have to search harder to find birds that thrive in more natural habitats,” says Emile DeVito, staff biologist at the New Jersey Conservation Foundation. “The birds are all still out there, but not in the numbers I remember in the 1970s, when trees were dripping with birds.”
In Delaware, 36 out of 136 species are vulnerable to climate change under a 3 degree C rise. If temperatures rise by 1.5 degrees C, that number is reduced to 17 species as vulnerable.
Species most threatened by climate change and sea-level rise in the First State include the Virginia rail, house wren, scarlet tanager, and great crested flycatcher.