Help Save Regional Forests

Hamilton Viewpoint: Duwamish Head Greenbelt, Seattle

The neglect of invasive plants is locking us in to future consequences that will affect timber, fisheries, agriculture, and recreational industries. Specifically, the spread of English ivy and holly will soon be unstoppable in regional forests. This ecological time bomb – horrific for its own sake – is clearly a financial time bomb for our state and economy.

It took 100 years for ivy to cover 50 percent of Seattle’s urban forests. English holly and laurel far outnumber native tree sprouts, and holly is doubling every six years, having “the potential to become a dominant species in both number of individuals and area covered within a few decades… and transform the region’s native forests on a large scale.” (Dr. David Stokes, UW Bothell).

It’s not a sensational forest fire or clearcut demanding media attention, but the neglect of invasives is far more threatening than any midnight chainsaw. If we want to maintain wildlife habitat, timber industries, recreational opportunities, slope stability, property values, and the natural sponge that filters our pollution, then all property owners and public land managers must do their part to control invasive seed sources. 

Losing diverse habitat is a serious health concern. Ivy infestations plus a food source (blackberry, unpicked fruit, bird feeders) are prime rat habitat (food and shelter). Lack of high biological diversity is hypothesized to have an increased risk of human and wildlife diseases (http://www.fao.org/docrep/009/a0789e/a0789e03.htm). A more recent study shows that plant diversity helps protect against asthma, while alien invasive plants increase asthma rates (https://phys.org/news/2018-06-added-benefit-biodiversity.html).

Even native birds spread ivy and invasive "seed rain."

What can you do?  Don’t let landscapers infect your woods with yard waste.  Don’t cut trees (unless hazardous) or take out stumps. Safely remove invasive plants from your property at the rate native roots are establishing so removal doesn’t affect the stability of a slope. Call a certified geotechnical engineer for landslide concerns (www.seattlegeotech.org/firms.html). Consider “vegetative management” (slowly replacing invasives with native plants) as a proactive approach to stabilizing forested slopes. Washington State Dept. of Ecology offers information (http://www.ecy.wa.gov/programs/sea/pubs/93-31/chap1.html) on stabilizing steep slopes and Puget Sound bluffs. King County Noxious Weed (http://www.kingcounty.gov/environment/animalsAndPlants/noxious-weeds.aspx) and Washington Native Plant Society (http://www.wnps.org/) have good invasive and native species information. 

Northern Flicker spreads beneficial seed rain from native Tall Oregon Grape (Mahonia aquifolium)