Historic Pa. Forest Faces Invasive Insect Threat
PITTSBURGH (AP) – A historic state forest filled with towering hemlocks is facing a serious threat from invasive insects, and scientists say climate change appears to be a contributing factor.
Cook Forest State Park, a National Natural Landmark, is known for its majestic, oldgrowth trees, some of which are over 140 feet tall. They help to create a cool, shaded environment for numerous creatures, including warblers, forest salamanders and brook trout.
But this week forestry officials said that tiny hemlock woolly adelgids had been discovered in the area, about 90 miles northeast of Pittsburgh, for the first time. The insect sucks the sap out of trees, and the pest has already caused massive damage to other forests.
“This discovery is especially unsettling,” Department of Conservation and Natural Resources Secretary Richard Allan said in a statement about the infestation in Cook Forest and nearby Clear Creek State Park.
Woolly adelgids, which are native to Asia, lay their eggs on the underside of hemlock branches, and the young insects feed on the sap of the trees, causing them to lose needles and die within five to 10 years. The insects appeared in Virginia in the 1950s and in southeastern Pennsylvania in 1969.
Scott Bearer, a forest ecologist with the Nature Conservancy, said scientists had hoped that such northern Pennsylvania forests would have “a little bit more time” before the deadly pest hit.
“It’s significant being in Cook Forest. There aren’t many old growth hemlock forests out there,” Bearer said, adding that in general, winters are getting warmer, and that's allowing the hemlock adelgid to move into areas where previously they haven’t been able to survive.
The Nature Conservancy is working with both state and federal forestry officials on ways to slow the spread, but treatments that use chemicals or a type of beetle that eats adelgids are expensive and slow.
Bearer said that the even bigger problem is that when hemlocks die off, other deep forest species are impacted, too. By shading large areas from direct sunlight, the forest floor stays cooler, creating habitat for creatures such as salamanders and brook trout.
“It’s a keystone species in the ecosystem. When the eastern hemlock die off we can expect a wide range of changes,” Bearer said.
Joe Elkinton, a professor of Environmental Conservation at the University of Massachusetts, said that previous research has shown that severe cold snaps are very effective in killing substantial numbers of adelgids, which lay eggs during the winter.
Elkinton was part of a UMass team that examined how the adelgid may spread if temperatures continue to increase, as expected.
“Certainly by any reasonable climate scenario it’s going to be throughout the northeast by century’s end,” Elkinton said. He added that use of beetles to control the spread has shown promising results in some areas, such as North Carolina.
A 2009 state report found there “is little doubt that Pennsylvania’s forest ecosystems are going to be affected by climate change in the coming decades” but noted that species such as hemlocks may be replaced by more southern trees such as oak and hemlock.
Christina Novak, a spokeswoman for the Department of Conservation and Natural Resources, declined to say whether the current administration believes the spread of the adelgids is related to climate change. She said experts believe that cold winters “can help slow the spread and size of the infestation.”
In the Cook Forest region, state officials plan to use insecticides and release the predatory beetles. The Bureau of Forestry is also drafting a hemlock conservation plan for Pennsylvania. The adelgid is now is found in 56 of Pennsylvania’s 67 counties.
Local businesses that rely on outdoor tourism are worried about the new infestation, too.
“It’s definitely concerning. It’s something that we’ve been paying attention to,” said Jody Fesco, a marketing manager at Gateway Lodge in Cooksburg, which has been in business since the 1930s.
“The hemlock is really our showcase species in the forest,” Fesco said.