HOBART — The tree seedlings planted here in the floodplains of Issaquah Creek may seem like native trees, with familiar names like Douglas fir, western red cedar and Sitka spruce.
But these are seedlings from far away.
They came from forests of Southwest Washington, Oregon and even Northern California, places with less rain and higher temperatures.
And they’re now part of an informal experiment on how climate change might shape Western Washington forests.
Foresters with the King County Department of Natural Resources and Parks are planting these trees from far-flung forests in hopes they’ll prove to be more resilient to the climate of the future. If these trees can survive the region’s wet, cold winters of today, they could be planted in parks and restoration projects across the county to withstand the droughts and heat domes of the future.
Summers are predicted to become hotter and drier, and already Pacific Northwest tree species — including the western red cedar — have experienced growth declines and die-offs in recent years.
These current and forecast changes in climate have led forward-thinking foresters and tree enthusiasts across the region to try out seed sources from areas farther south with climates that are predicted to resemble Washington between 2070 and 2100 in a process sometimes called “assisted population migration.”
King County will be checking on these trees over the next few years to see if they establish successfully, said Paul Fischer, a senior forester with King County Parks.
“I think they’ll do great in 50 to 75 years, but if they don’t survive the first five years, then it doesn’t really matter,” Fischer said.
Fischer is calling the project a “trial” since the experiment is not as sophisticated as an academic research study.
In total, the county is trying out seeds sourced from 19 places, planting them here and at three other King County sites, including Taylor Mountain Forest, Neely Bridge Natural Area near Auburn and a site on Maury Island.
Each site is around 2.5 acres and will host control seeds that are locally sourced and seeds from outside Western Washington. By the end of the week, crews will have planted around 5,700 trees as part of the trial.
How well each seedling does could influence what King County plants in its restoration work going forward. The county oversees over 32,000 acres of open space, of which around 28,000 is forested. In a typical year, the county plants between 30,000 and 50,000 trees, Fischer said.
Ponderosa pines are among the six tree species planted at the trial sites (which also include grand fir and western hemlock). Ponderosas are more prevalent in Eastern Washington, and King County staff debated whether to include the species in the trial, said Kathleen Farley Wolf, King County’s forest conservation director.
Ultimately, ponderosas were included because they could be useful to plant in areas where Douglas firs struggle — and there are already stands in King County and near Joint Base Lewis-McChord, she said.
“What we’re trying to do is maintain our native forests with that same range of native species … and just provide some support to some of those species that may not be genetically as well-adapted,” Farley Wolf said.
King County isn’t the only one doing this type of trial. The Washington State Department of Natural Resources, which grows commercial stands of trees to generate revenue, is working with the U.S. Forest Service and other state agencies to grow Douglas fir on 18 West Coast sites with seeds from 23 environments.
There is also another trial site within the Tolt watershed, east of Seattle, where seeds sourced from outside Western Washington were planted in a project facilitated by Seattle City Light, Seattle Public Utilities, the Northwest Natural Resource Group and other organizations.
King County’s work is funded by the county’s parks levy, which is up for renewal this year. The trees for this project cost around $35,000. That’s about $21,000 more than what this number of trees typically costs the county if it sourced them locally, according to Fischer.
“We get quite a bit of bang for our buck on this project. It’s not a really expensive one and will give us a lot of good data,” Farley Wolf said.
