If you stand very quietly in the Harvard Forest, you’ll hear a soft whispering sound. It’s not the wind, it’s the sound of falling hemlock needles. An invasive insect called the hemlock woolly adelgid is threatening to overtake hemlock trees across the East Coast, and the protected forest in Petersham, is no exception.
“It’s like the hemlocks are being clear-cut by these little bugs,” said Crystal Schaaf, professor of remote sensing in UMass Boston’s School for the Environment. The invasive insects feed on the twigs from the hemlock branches, causing the needles to fall off. “You’re standing in this grove of really big trees, and a rain of needles is coming down on your head.”
Schaaf has received a Charles Bullard Fellowship in Forest Research from Harvard University. She will spend her fellowship year working in the Harvard Forest to find new ways to track the hemlock woolly adelgid, assess its impacts, and hopefully contribute to efforts to slow its proliferation.
The fellowship was established in 1962, and attracts scholars from the sciences and humanities, as well as professionals in the public and private sectors. The fellows’ research contributes to a greater understanding of forest ecology and policy.
Schaaf is a noted expert on remote sensing. She uses both terrestrial and satellite imaging technology to map forest canopy structure around the world, and works with NASA on several satellite science teams. Schaaf will work with David Orwig and other Harvard Forest researchers to apply these techniques in Petersham. If Schaaf and Orwig can better monitor the invasive species, they may be able to find some stands of trees that are more resistant to infestation.
“We don’t have terribly good ways to monitor the spread of these insects, because it tends to first affect the lower branches,” said Schaaf. “The tops are still staying green. If you fly aircraft overhead, you don’t necessarily see the extent of the damage until the trees are nearly dead. People on the ground have to monitor the spread by flipping over the branches one at a time and looking for the characteristic white woolly egg sacs.”
The consequences of losing the hemlock, a foundation species in New England forests, would be devastating to the environment. Hemlocks grow near streams and rivers, and their year-round shade keeps water from evaporating in summer, and keeps snow from melting too quickly in spring. The warmer winters associated with climate change are causing the adelgid to spread northward and hastening the destruction of these important trees.