Native ash trees make up a large part of the urban forest in the Portland metro region. The urban forest not only lines our streets, shades our homes, and enhances our region's livability. It is essential for birds, insects, and the other wildlife—like salmon. Native ash trees growing along streams like Johnson Creek and the Columbia Slough shade the water keeping water temperatures cool and welcoming for salmon and other wildlife.

Ash trees around the country are currently threatened by an invasive species of insect called the emerald ash borer. The emerald ash borer is the most destructive and costly invasive insect in U.S. history. Although not currently here, the emerald ash borer is predicted to reach the Portland metro area in the next 5-10 years and devastate the region's ash trees.

Property surveys

To better prepare for the emerald ash borer's arrival, Environmental Services is conducting a survey to assess the location and number of native ash trees in key areas in and around Portland. More than 250 properties located in the Johnson Creek and Columbia Slough watersheds have been randomly selected to participate in the survey. The survey will help us better understand the insect's potential impact to our region's urban forest. 

The survey is expected to take place between June and October 2020. Survey participants will receive a letter in the mail asking for permission to access their streamside property to count the ash trees. If you've received a letter and would like to grant permission online, please fill out this form.

For questions about these surveys or our study, please contact Dominic Maze at dominic.maze@portlandoregon.gov or 503-823-5988.