Trees in the city — any city — have got it hard.
If an urban tree is lucky enough to be in a park or other protected place, it still has to deal with air pollution, tree-killing non-native plants and forest diseases that thrive in the urban environment. Now it turns out, our urban arboreal pals may also be suffering from a deadly fever.
New scientific research published two weeks ago found that trees across the West are dying in increased numbers due to rising temperatures. The regional temperature increase is likely due to global warming. The startling new findings underscore the importance of local tree-planting and stewardship efforts in order to keep our community green.
Scientists from several research institutions, including the University of Washington, have been monitoring long-term tree mortality at several sample locations across the West. They found that tree mortality, on average, has doubled in the past two decades. During that time, the average temperature across the West has risen by 1 degree Fahrenheit. The researchers ruled out other potential factors for the increased rate of tree death, such as air pollution and fire suppression. They put the blame squarely on the heat.
While one degree may not sound like a lot, it is when averaged across such a large landscape. The current temperature increase in the West has been enough to reduce snowpack (and melt glaciers in the Cascades), cause earlier snowmelt and exacerbate droughts. The higher temperatures also favor pests and diseases that make life tough for trees.
The result is that trees are dying faster than they can be replaced naturally. The long-term impact, according to researchers, could mean thinner forests, smaller trees and vastly different forest ecosystems.
But in urban areas, the effects of rising temperatures could well be more pronounced.
Here in the Puget Sound region, our urban forests are already threatened by a collection of stressors that include development, invasive plants and disease. Global warming throws another straw, albeit a heavy straw, on the proverbial camel’s back.
As part of our work to conserve and restore the Hylebos Creek Watershed, the Friends of the Hylebos and hundreds of volunteers plant thousands of trees each year in Federal Way and surrounding communities. Through this work, I’ve seen firsthand the condition of urban forests in and around Federal Way.
Invasive plants threaten forest health throughout the city. Parks along the city’s northern shoreline are being choked out by English ivy. At the city’s southern end, where the Hylebos flows, Himalayan blackberry is the primary invasive plant plaguing forests. Both are bad news for trees.
Additionally, many of the forests in our parks are dominated by deciduous trees like maples and alders that are nearing the end of their lives. Healthy Pacific Northwest forests should be dominated by long-lived conifers. However, our altered landscape does not have a sufficient population of young firs, hemlocks, cedars and spruces. When the deciduous trees eventually die, there won’t be enough conifers to replace them. The resulting tree gap would create yet another opportunity for invasive species to take over the forests.
When you add rising temperatures to the mix, the future of urban forests could look even grimmer. Fortunately, the Federal Way community has a great track record of volunteer tree plantings and forest stewardship. Hundreds of volunteers have helped maintain the forest at the West Hylebos Wetlands, removing truckloads of invasive plants and planting native trees and shrubs. Similar work has taken place at sites around Hylebos Creek.
For many Federal Wayers, verdant conifer forests epitomize Pacific Northwest living, and we treasure the publicly protected forests on parks like the West Hylebos Wetlands and Dash Point State Park. According to the latest science, it sounds like we’ll need to plant even faster.
If you’d like to get involved in tree planting or other volunteer stewardship activities, contact Hillary Kleeb at streamteam@hylebos.org or (253) 874-2005.
