Washington is home to 2.7 million acres of forest landscape in need of urgent restoration. Scientists are looking to trailing edge forests, areas that are expected to experience range contraction and possible landscape conversion, for insight and lessons on how to manage this ever-changing landscape.
A new study conducted by the Washington Department of Natural Resources and The Nature Conservancy sought to localize and improve understanding of the trailing edge forests in the eastern Cascades of Washington by mapping and characterizing their composition, structure, ownership, recent fire activity and climate vulnerability. Trailing edge forests are characterized by dry conditions, mixed-conifer species and variable land ownership. The study found that these factors increase the risk of forests transforming into novel forest or non-forest land cover types as drought, wildfire, and climate change accelerate. For example, following a fire in a trailing edge forest, species that were previously found might not regenerate leading to different species dominating the landscape and creating a novel ecosystem.
After a fire, healthy forests can recover and even thrive but trailing edge forests conditions leave these areas more susceptible to ecosystem shifts. Credit: TNC/Zoe van Duivenbode
“High-severity fire followed by drought is a critical sequence that can hinder tree regeneration and dramatically alter forest landscapes,” said lead author, Dr. Garrett Meigs, Forest Health Scientist, Forest Resilience Division, Washington State Department of Natural Resources.
Key findings:
Trailing edge forests encompass 21% of the currently forested landscape across the eastern Cascades study area, illustrating that projected drought and wildfire have the potential to transform large areas of forests to novel forest conditions or non-forest land cover types.
Recent wildfires have affected a similar percentage of trailing edge and other forests (21% and 25%, respectively), but fires in trailing edge forests with less dense vegetation were less severe.
The patchwork and variations in land ownership (i.e. mix of private and public ownership) across trailing edge forests present a unique set of management challenges and opportunities, with specific concerns for carbon storage, water quantity, jobs, and community wildfire protection.
“Our study shows that trailing edge forests are widespread across the Eastern Cascades of Washington,” Meigs said. “Although these areas have not experienced very much high-severity fire in recent years, trailing edge forests could be primed for transformation in the future, so now is an important time to develop collaborative adaptation strategies.”
As climate change progresses, the increasing frequency and intensity of wildfires pose a significant risk to forest health, starting with trailing edge forests. Credit: TNC/John Marshall.
Trailing edge forests will be a critical indicator of forest health as the impacts of climate change continue to increase. Land managers will be better able to understand how disturbances such as a wildfire can lead to ecosystem change or impact the return to historical patterns and processes within a forest ecosystem. While additional research is necessary to understand how a disturbance alters the forest ecosystem and leads to ecological tipping points, this paper lays the groundwork for improving forest management and climate resilience of Washington’s complex forest systems.
“As forests in eastern Washington are expected to shift and transform in the coming years, there will be both challenges and opportunities for adaptive management,” explains co-author, Dr. Michael Case, Forest Ecologist with The Nature Conservancy in Washington. “Although some of these forests are expected to transition to non-forest vegetation in the future, if we act now, we have the greatest opportunity to respond to these changing conditions, support decisions and collaborative partnerships, and find solutions that work for people and the environment.”
For media inquiries, contact:
Emily Heber, TNC media relations manager, emily.heber@tnc.org
Featured image: Forest recover following a wildfire a few seasons before. Credit: TNC/Zoe van Duivenbod
