City forests in peril: Invasive plants are killing native trees
Restoration efforts rely heavily on volunteers
Under a damp awning of yellowing bigleaf maples, Judith Starbuck is laying waste to a patch of English ivy. A vine at a time, she rips and tugs at the menace creeping through Madrona Woods.
Starbuck and a small band of mud-stained volunteers are reclaiming these woods, saving native trees and shrubs from the stranglehold of fast-growing foreign invaders.
The sloping park, covering more than 9 acres above Lake Washington, is a valuable piece of urban forest -- a refuge where people can hike, learn a thing or two about nature and shed the stress of living in a big city.
Seattle's forests, though, are in trouble.
Thanks to decades of neglect, many of the city's parks and greenbelts are plagued by smothering ivy, Himalayan blackberry, holly, laurel, morning glory and other undesirables. Half of the acreage is seriously invaded, surveys show.
The invasion is unrelenting. Now, as many trees are dropping their leaves and taking a winter rest, the weedy vines keep growing, throttling native vegetation.
"We're losing the urban forests," said Cass Turnbull, founder of PlantAmnesty, a Seattle non-profit that works to protect trees.
In the worst cases -- such as the greenbelt running along the west side of the Duwamish River, Ravenna Park and Kinnear Park on the southwest edge of Queen Anne -- parts of the forest are completely overrun by invasive species.
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"We're going to be left with fields of dead trees covered with ivy," warned Pieter Bohen, head land manager for the Cascade Land Conservancy.
If the invasion of foreign weeds isn't stopped, his group predicts, nearly three-quarters of the forested parks will become "ecological dead zones."
Restoring the city's 2,500 acres of wooded parks to healthy conditions would cost $48 million over the next two decades, estimates from the non-profit group show. And that's only to help the park trees.
There are also 120,000 trees lining Seattle's streets, and while the city claims responsibility for up to 40,000 of them, there are only two city arborists working to keep them healthy in a hostile environment.
Private trees, in most cases, receive no protection at all. Landowners with a developed piece of property can level every tree on their lot with no permits, no restrictions. At least one neighborhood bans trees taller than rooftops, resulting in the butchering of trees through pruning, if they are planted at all. Increasingly, modest single-family homes are being razed to make way for mega-houses or apartments, squeezing out vegetation.
The problem with weeds began a century ago, when Seattle was widely clearcut.
Native deciduous trees, mostly maples and red alders, grew back. In healthy Northwest woods, conifers -- Douglas firs, Western red cedars and pines -- would have grown up under their branches to gradually replace them. But those trees didn't take hold, initially because the clearcuts left few seed sources and later because of competition with weeds.
Today, seven out of 10 mature trees in the urban forest are bigleaf maples -- and they are reaching the end of their lifespan. All over the city, experts say, the trees are dying.
Continue reading this story from the Seattle P-I:
City forests in peril: Invasive plants are killing native trees
