Saving Seattle's Native Urban Forests

When people think of Seattle and the Pacific Northwest in general, images of dense forest with towering trees come to mind. But, like many other areas, the natural parklands in the city are under serious threat from invasive species. A century ago, when Seattle was a young growing city, much of the area was clearcut for development. Few of the grand conifers that populate the forests of the Northwest remained to produce new offspring. The area was largely repopulated with deciduous trees like maple and red alder. Strong competition from invasive species kept the conifers from regenerating. Now many of the bigleaf maples, the most common tree in Seattle's urban forest, are nearing the end of their lifespan and an invasion of aggressive weeds is taking their place.

People have generally had the idea that wild areas, including urban forests, take care of themselves and need little management. Weeds gradually crept in and began to push native species aside. Invasive species are survivors. Some smother and crowd out other species, some alter the soil chemistry to their own advantage, and some can spread vigorously by vegetative means or are prolific producers and distributors of their seeds. The Seattle Post Intelligencer reports, "Now, there's enough ivy on public land here to cover more than 630 football fields — and enough blackberries to top more than 900, research shows."

Clearing away invaders like ivy or Japanese knotweed is a daunting task. Seattle, like most areas has limited funds to care for its urban forest and parkland. Although new trees are planted, without sufficient resources to care for them many will not survive. Volunteers have stepped in to help, but it would take an army to clear away the vast amount of weeds that have taken hold.

Many of the most vexing invasive weeds are introduced ornamentals that have escaped from people's gardens. Gardeners can help limit the spread of invasive plants by removing them from their properties and not choosing them for their gardens. Several invasive species are still available at nurseries or may be spread by unknowing gardeners. Take time to learn about the common invasive species plaguing your area.

Links:

• Urban Forests Under Siege a special report from the Seattle Post Intelligencer with articles on the spread of invasives, the impact of urban growth and the biodiversity of Seattle's urban forest - including links and resources of interest


• Volunteers spend a soggy, muddy holiday helping a park an article on the experience of volunteers clearing invasives from a Seattle park from the Seattle PI


• Simple solutions for invasive plants from the Seattle PI

Links to groups fighting invasive plants and a few invasive plant list. Search the internet for groups and list in your area.

• Washington Invasive Species Coalition (Washington state, USA)


• WSNWCB Weed List (Washington state, USA)


• Invasive Plant Alert (Government site of British Columbia, Canada)


• Ivy Busters (a local Vancouver BC organization)


• Invasive Plants of Natural Habitats in Canada a publication from Environment Canada


• Canadian Botanical Conservation Network (Canada)


• Global Invasive Species Database from The World Conservation Union (IUCN) Invasive Species Specialist Group (ISSG) - (international)


• Alien Plant Invaders of Natural Areas (United States)


• Noxious Weed Program alerts and fact sheets from the United States Department of Agriculture

Posted by Eric La Fountaine at 1:21 PM on February 10, 2006

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