Invasive Beetles Put Oregon Forests at Risk

Two invasive beetles could pose a significant threat to Portland’s tree canopy, according to state foresters and researchers, reports April Erlich for OPB, limiting the effectiveness of trees as a tool for reducing the urban heat island effect.

One pest, the emerald ash borer, could decimate the ash species that make up 5 percent of Portland’s urban residential tree stock. “Outside of urban areas, the ash borer could kill trees that shade streams and rivers, in turn making those waterways warmer. That’s bad news for the Willamette River, which is already struggling to meet federal regulations on temperature.”

The Mediterranean oak borer, another beetle, “tunnels beneath an oak tree’s bark, carrying with it a fungus that grows within the tree and becomes the borer’s main food source. The fungus can cause a disease called oak wilt, which blocks trees’ ability to take in water and nutrients. Infected trees typically die within a few years.” 

Together, these two new threats could spread and have a major impact on Oregon forests and limit the beneficial impact of trees on urban air quality, temperatures, and public health.