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Filling The Canopy: Volunteers Replace Trees Killed By Invasive Species

Sarah Schneider
90.5 WESA News

In an urban forest, trees don’t just provide aesthetics, they prevent river overflow and filter pollution.

Since the early 2000’s, tens of millions of North American ash trees have been killed from a non-native insect, the emerald ash borer, that arrived via shipping pallets in Michigan. The eastern Asia beetle has killed thousands of Pennsylvania trees and nearly 50 in Pittsburgh’s Riverview Park.  

In an effort to recreate what has been lost, volunteers and the Pittsburgh Parks Conservancy worked Wednesday in the park to plant 100 trees.

It takes about four years for the beetle to kill the tree, leaving behind patches of open canopy. When this happens, invasive plants can aggressively grow because they don’t have competition from native plants.

Bryan Dolney, a field ecologist with the conservancy, said eastern United States forests that go through four seasons require a closed treetop canopy to keep out sunlight to halt growth of invasive plants. Plus, it provides other benefits.

“When we look up into the tree canopy we can see that there’s blue sky here, and the more trees we have fill in this area we can protect from storm water management, it can make the area cooler and in the winter it can protect from wind,” he said.

Once planted the trees require a lot of volunteer upkeep such as watering and cutting away non-native plants growing near them.

There are also about five times as many deer in the park as there should be, according to Erin Copeland, a senior restoration ecologist with the conservancy. She said the volunteers protect the saplings with fencing and structures made from fallen trees. Something like Lincoln Logs, she said.

Without intervention, Copeland said something would eventually grow in the openings, but it’s best to put native species back.

That’s a long process, she said.

Faster growing species could reach canopy height in 10 years, but most will take two decades.