This Is Where We Live

Mt. Hood
Photo by Pete LaMotte

The Clackamas, Clark, Multnomah, and Washington County CWMA (informally known as the 4-County CWMA) exists to create and support collaborative weed management among land managers and owners in and around the greater metropolitan area of Portland, Oregon. Noxious weeds extend across multiple ownerships and travel over the landscape. For this reason, collaboration and partnerships are essential for effective management. In addition, partnerships can provide access to new sources of funding and increase implementation efficiency. The CWMA promotes weed education/outreach, weed inventory and prevention, and weed control activities.

What exactly is the 4-County area?

Photo by Paul Stevenson

The 4-County area is the combined area of Clackamas, Multnomah, Washington, and Clark Counties, totaling 3,727 square miles.  It is a region rich in wildlife, natural features, and recreational opportunities, composed of both urban and rural zones.  Within the 4-County area parts of both Mt. Hood National Forest and Willamette National Forest can be found, as well as the beautiful Columbia River Gorge and part of the Cascade Range.  Dozens of neighborhood parks, like Oxbow Park, and wildlife refuges, such as the Ridgefield Wildlife Refuge and Tualatin River National Wildlife Refuge, can be found within its boundaries.

Important watersheds, including the Bull Run Watershed, are located within the 4-County area.  There are hundreds of miles of hiking trails to be found here, where you might spot native animals such as beaver, bald eagle, elk, salmon, and bobcat, and native trees like the Douglas fir, Western redcedar, Hemlock, and Bigleaf Maple.

How do invasive species affect the 4-County area?

Imagine walking your favorite trail in Mt. Hood National Forest, keeping your eyes open along the way for the colorful native wildflowers you’re used to seeing there.  But to your surprise, you see only a few blooms left where once where were many!  This may well be the work of a crafty invasive weed known as Garlic Mustard, which out-competes native plants for nutrients and sunlight.

This scenario is already taking place on many scales in the 4-County area.  Invasive plants, which are often more adaptable and lacking natural enemies, deprive native species of essential nutrients, sunlight, and water.  Once the native species have begun to disappear from an area, biodiversity declines.  The monoculture which is left offers little to no nutritive value to local wildlife, whose populations suffer as well.  Invasive plants are the second leading cause of species extinction worldwide.

Invasive species also reduce erosion control along streambanks, and limit the growth of shade trees over waterways.  Less shade means increased water temperature, which reduces oxygen levels for fish and encourages algae growth.

Invasive species usually spread quickly and easily, which is why prevention and early detection are critical.  These weeds affect more than just the plants they out-complete – they affect wildlife, waterways, and the entire ecosystem, and even incur economic costs.  Some economic impacts include loss of revenue in nursery, farming and timber industries, increased roadside and power line maintenance costs, and an increased cost in maintenance of drainage ditches.