New research suggests that old-growth forests with large trees and a wide range of species and tree sizes could be helpful in helping some bird species deal with the continued negative effects of climate change.
In a study published Friday in the journal Diversity and Distributions, researchers from the College of Forestry at Oregon State University studied a total of 13 bird species with extensive records in the U.S. Geological Survey’s annual Breeding Bird Survey. Out of those birds, there were only two species – the Wilson’s warbler and hermit warbler – that were affected adversely by global warming over the past three decades. But the study suggested that both species’ population figures were stable or increasing in regions that are rich in old-growth forest.
According to a press release published in EurekAlert, the researchers studied a number of factors in order to conclude that high concentrations of old-growth forest can potentially help some threatened bird species. These included bird population figures, forest structure, and climate in specific parts of northwestern North America. The team, which was led by OSU College of Forestry professor Matthew Betts, also used satellite imagery to estimate how much old-growth forest was found within about 450 yards of the different bird survey routes.
As there haven’t been too many management recommendations from previous studies on biodiversity and climate, Betts said in a statement that his study underscores the importance of old-growth forest conservation.
“Managers hoping to combat the effects of climate change on species’ populations may now have an additional tool – maintaining and restoring old-growth forest.”
The Audubon.org fact sheet for the Wilson’s warbler suggests that their numbers are “probably stable,” and that the creatures are “probably not threatened” by deforestation. The birds spend winter in Mexico and spend the late spring and early summer breeding along the West Coast, and also in various parts across northern North America, including Alaska, New England, and the Canadian Maritimes. Currently, this species’ population is declining by about two percent per year in the Pacific Northwest.
Likewise, the hermit warbler also winters in Mexico, but unlike the Wilson’s warbler, its breeding grounds are exclusively found in the West Coast. This species’ population is also stable, but the researchers noted that its numbers have been on the decline in parts of North America where old-growth forest is less common.
Although the new study suggests that old-growth forests alleviate the effects of global warming on birds, more research is still needed to find out the features in these forests that drive the newly-discovered phenomenon. Betts’ team has a few theories at the moment, including the possibility that large trees serve as “heat sinks” that keep temperatures reasonable during unusually warm stretches. They also speculated that multiple canopy layers in old-growth forests could also be instrumental in moderating the effects of climate change.