Help Save Regional Forests

Hamilton Viewpoint, Seattle - a view of invasives

Invasive seed sources on private land continually reinfest restored public forests. The unchecked spread of invasive plants into regional forests will lock us in to future consequences that will affect timber, fisheries, agriculture, and recreational industries. English ivy and holly may soon be unstoppable – if we do nothing. Slow ecological decline, horrific for its own sake, is clearly a time bomb for our state and economy. Widespread landowner participation is critical to a solution.

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

The spread of invasives is not an illegal clearcut or sensational forest fire demanding media attention, but it’s far more threatening than any midnight chainsaw. If we want to maintain pollinator habitat, slope stability, stormwater protections, and ecological checks & balances, then property owners and public land managers must do their part to control invasive seed sources and replant native plant communities.

Habitat diversity keeps insects and diseases in check. For example, ivy and blackberry provide food and cover for rodents, with the known disease vector of rat infestations. Lack of high biological diversity is hypothesized to have an increased risk of human and wildlife diseases (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2673579/). Plant diversity has been shown to help 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? Cut ivy vines from trees to save the tree and prevent ivy from going to seed. Don’t cut trees (even if invasive) if their roots are holding your slope. Remove invasive plants from your property at the rate native roots are establishing. Contact a certified geotechnical engineer (www.seattlegeotech.org/firms.html) or call 911 for immediate landslide concerns. Consider “vegetative management” (replacing invasives with native plants) as a proactive approach to stabilizing forested slopes – this is primarily the work of Garden Cycles LLC – a field distinctly different than “landscaping for beautification.”

Do-it-yourself Resources:

  1. Step-by-Step Guide: Your Yard as Urban Forest.
  2. Slope considerations (by Greenbelt Consulting): LIVING NEAR THE EDGE OF PUGET SOUND.
  3. Washington State Dept. of Ecology: Stabilizing slopes on Puget Sound bluffs: (https://ecology.wa.gov/Water-Shorelines/Shoreline-coastal-management/Hazards/Puget-Sound-landslides/)
  4. King County Noxious Weed Department: Information on Invasive Plant Species (http://www.kingcounty.gov/environment/animalsAndPlants/noxious-weeds.aspx)
  5. Washington Native Plant Society: Native plant species (http://www.wnps.org/)

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

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