Friday, October 19, 2007

Donora Ravine Restoration

Map of Donora Ravine

Donora Ravine is a small place as ravines go. But for some local residents it is now a big issue. Late last year the city began a restoration project of the degraded site. The controversy began when the city cut down all the Norway Maples (Acer platanoides) surrounding the ravine. While this is an important first step in the restoration process, cutting down mature trees is a touchy subject for city residents, especially if they don't realize the impact this species has on the natural environment.

Norway Maples are an introduced species that are commonly planted as a street tree. They grow fast, produce a dense canopy of shade and can tolerate a variety of urban conditions, ie. salt tolerance, drought resistance, and soil compaction. They also produce large volumes of seeds that readily sprout everywhere including our ravine parks. Left unattended they can out-compete the slower growing Sugar Maple (Acer saccharum).

While the result may be a little unsightly in the short term, in about 10-15 years the woodland will re-establish, this time with native species. Friends of the Don East have been busy this year planting native trees and shrubs. Already there are signs of abundant understory growth. The stumps of the maples were left in place because these will provide valuable habitat for tree dwelling animals including Raccoons and Wood Ducks (Aix sponsa). Woodpeckers also feed here on insects living beneath the bark.

In order to educate the public, the city erected an interpretive sign that describes the restoration project and its importance to the natural environment. It will be interesting to watch this site mature over the next couple of years.

View of ravine taken December 2006. Viewpoint is arrow #1

Donora Ravine, 10 months later. Viewpoint is arrow #2

Father and daughter read intrepretive sign beside ravine

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