In late July, emerald ash borer (EAB) beetles were confirmed at Jackson Bottom Wetlands Preserve, with multiple Oregon ash trees showing canopy decline consistent with infestation.

While this is the first confirmed detection at Jackson Bottom, its presence is not unexpected. EAB has already been confirmed throughout the region, including nearby Forest Grove in 2022, Portland, and other areas of Hillsboro.

What is Emerald Ash Borer?

Emerald ash borer is an invasive beetle that attacks and kills ash trees. Its larvae feed beneath the bark, disrupting the movement of water and nutrients within the tree. Once infested, an untreated ash tree may decline rapidly and eventually become structurally unstable. EAB does not directly threaten people or pets, but its impact on ash trees creates significant ecological, operational, and public-safety challenges.

Proactive Restoration Efforts

After the detection of EAB in Forest Grove in 2022, Parks & Recreation staff launched a proactive forest restoration and ash management program at Jackson Bottom.

"While confirming the emerald ash borer at Jackson Bottom is important, it does not change the work we have already been doing to prepare for its arrival," said Natural Resources Manager Laura Trunk. We knew EAB would eventually reach Jackson Bottom, which is why we immediately began managing our Oregon ash trees, protecting high-value trees, and replanting the area with a diverse mix of native trees. This gave the forest time to transition gradually rather than experience a sudden and widespread loss of canopy.

"The emerald ash borer will change this landscape, but it does not have to mean the total loss of the forest. The restoration work that is currently underway will help maintain the forest canopy, improve wildlife habitat, protect water quality, and create a healthier forest."

Grant funding from the Tualatin Soil and Water Conservation District, Oregon Department of Forestry, Oregon Watershed Enhancement Board, and Metro supported the City's efforts to begin this restoration work and reduce future safety risks through strategic forest management. This long-term effort will build a more resilient forest that protects watershed functions and ensures the preserve continues to serve the community for future generations.

Parks & Recreation and Public Works staff continue to assess and plan for mitigation and impacts to Hillsboro parks and natural spaces as EAB spreads. Learn more about the City's ongoing efforts to monitor, manage and prepare for EAB.