Old growth forests offer refuge

Old forests that contain large trees and a diversity of tree sizes and species may offer refuge to some types of birds facing threats in a warming climate, scientists have found.

In a paper published in December 2017 in Diversity and Distributions, a professional journal, researchers in the College of Forestry at Oregon State University reported that the more sensitive a bird species is to rising temperatures during the breeding season, the more likely it is to be affected by being near old-growth forest.

Researchers studied 13 bird species that have been tracked annually in the U.S. Geological Survey’s annual Breeding Bird Survey, one of the most comprehensive efforts of its kind in North America. Only two — the Wilson’s warbler and hermit warbler — showed negative effects from rising temperatures over the past 30 years, but actual counts of both species show that their populations are stable or increasing in areas that contain high proportions of old-growth forest.

A team led by Matthew Betts, professor in the College of Forestry, reached their conclusions by analyzing data for bird populations, forest structure and climate across northwestern North America. The researchers used satellite imagery to determine the amount of old-growth forest within about 450 yards of each 25-mile-long bird survey route.  Read the full press release.