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King County foresters are testing native tree seedlings from warmer, drier climates to promote healthy, climate-resilient forests
Summary
March 20, 2025: Foresters at the Department of Natural Resources and Parks are conducting trials to determine if trees grown from seeds acquired from Southwest Washington, Oregon, and Northern California are more productive and can withstand heat and drought better than trees grown from locally sourced seedlings.
News
King County foresters are planting native tree seedlings acquired from warmer, drier climates for a long-term study designed to promote healthy, resilient, and productive local forests.
Based on climate modeling that predicts conditions at the end of the century, the King County Department of Natural Resources and Parks secured tree seedlings from Southwest Washington, Oregon, and Northern California. Forest specialists selected four planting locations throughout King County that have different site conditions and will monitor the trees’ survival and health multiple times over the next decade.
The climate-adaptive tree planting trials are one of the strategies included in King County’s 30-Year Forest Plan launched by Executive Dow Constantine to promote urban and rural tree canopy and improve forest health and productivity for current and future generations.
"We are taking action to ensure that the forests of King County – recognized around the world for their ecological value and spectacular beauty – remain healthy and productive into the next century,” said Executive Constantine. “The study conducted by our scientists today will inform tree planting for a more climate-resilient future.”
The goal of the study is to answer one primary question: Do seedlings grown from seed collected in regions with warmer, drier climates have a better chance of surviving and thriving in King County as the local climate changes?
Foresters at the Department of Natural Resources and Parks used a mapping program developed by the U.S. Forest Service that helps forest stewards find the right seeds for their planting sites based on climate predictions. They chose the 2071-2100 timeframe – the furthest timeframe available – and identified locations that currently have climates similar to what is predicted for King County by the end of this century.
The project team selected Douglas-fir, western redcedar, Sitka spruce, grand fir, western hemlock, and ponderosa pine species for the study. They are trying to identify genotypes of native species that might be better adapted to a changing climate rather than assist with the migration of species that are not currently found in King County.
After preparing the designated sites, crews planted a combined 5,700 trees in early March at four locations stewarded by King County: Taylor Mountain Forest, Middle Issaquah Creek Natural Area, Neely Bridge Natural Area near Auburn, and Vashon-Maury Island. They will return to each location during the second, fifth, and 10th years of growth to monitor the trees’ health, and comparing the response of seedlings grown for seed collected in other regions to growth exhibited by seedlings sourced locally.
The trial results will inform future tree plantings coordinated by King County and will be available to other public and private forest managers. King County Parks is a steward of 32,000 acres of open space, of which 28,000 acres is forestland.
The Department of Natural Resources and Parks has expanded its Forest Stewardship Program since 2022 with funding generated by the King County Parks Levy, hiring additional foresters, forest technicians, and specialists to prepare local forests for climate impacts. The tree-planting trials are also funded by the King County Parks Levy.
“Forests in our region play an important role in climate change mitigation, but they are also vulnerable to climate impacts that include drought and heat,” said Kathleen Farley Wolf, Director of King County’s Forest Conservation. “With funding generated by the King County Parks Levy, our forest stewardship team is developing strategies to prepare our local forests for climate impacts, making it possible for them to store more carbon in the future and improve habitat today.”
“Our forest experts are applying the latest climate science to make sure future generations can enjoy the spectacular forests that define our landscape,” said John Taylor, Director of the Department of Natural Resources and Parks. “Their actions will promote resilient, productive forests that continue to store carbon and provide healthy outdoor recreation in the future.”
Promoting healthier, more resilient forests contributes to King County’s Strategic Climate Action Plan, a comprehensive 5-year blueprint that will be updated this year by the Executive Climate Office.
"From storing carbon to improving air quality, forests play a critical role in reducing emissions and cooling King County as the climate changes," said King County Climate Director Marissa Aho. "This work supports efforts to protect those benefits and preserve natural gems of the Northwest.”
We are taking action to ensure that the forests of King County – recognized around the world for their ecological value and spectacular beauty – remain healthy and productive into the next century. The study conducted by our scientists today will inform tree planting for a more climate-resilient future.
Our forest experts are applying the latest climate science to make sure future generations can enjoy the spectacular forests that define our landscape. Their actions will promote resilient, productive forests that continue to store carbon and provide healthy outdoor recreation in the future.
From storing carbon to improving air quality, forests play a critical role in reducing emissions and cooling King County as the climate changes. This work supports efforts to protect those benefits and preserve natural gems of the Northwest.
Forests in our region play an important role in climate change mitigation, but they are also vulnerable to climate impacts that include drought and heat. With funding generated by the King County Parks Levy, our forest stewardship team is developing strategies to prepare our local forests for climate impacts, making it possible for them to store more carbon in the future and improve habitat today.
Contact
Doug Williams, Department of Natural Resources and Parks, 206-477-4543