Oregonians don’t exalt ash trees the way they do other native trees. That’s no slight to the good people of Oregon. It’s a statement to the awe-inspiring species that demand humble, neck-strained observation and intentional stewardship.
Oregon ash (Fraxinus latifolia) logs won’t turn a profit the way Douglas-fir timber does. It’s unlikely to appear on a hipster’s tattooed forearm like a Western redcedar. And nobody would claim it ages gracefully the way an Oregon white oak does. While its vigor for life would be welcome among houseplants, many people describe this enthusiasm as messy or, dare we say it, even weedy.
Upon its arrival in Oregon, the invasive emerald ash borer (EAB) cast a shadow on all species of ash trees, particularly Oregon ash. While geneticists maintain hope that EAB-resistant ash varieties can be developed in the future, it’s certain that most ash trees growing today will eventually become infested and die. News of any species’ demise is sure to invoke feelings of sadness and loss. But for an under-loved tree like Oregon ash, those feelings may be fleeting or replaced by gratitude that a money-making or prettier tree was spared a similar fate.
The impending loss of ash is forcing restoration ecologists to explore new ways of doing their work.
Oregon ash, although lacking glamour, is an important tree species that’s been heavily relied upon to revitalize parts of the Tualatin River watershed. Tualatin SWCD and our partners use a variety of tactics to improve the health of the Tualatin River, its tributariesTributary A river or stream flowing into a larger body of water., and the land in between. Shading waterways by planting trees and shrubs is a major component of this conservation effort. Knowing which plant to put where is equally important because every species thrives under certain conditions – this is called a species’nicheNiche The specific area where an organism lives..
Oregon ash occupies a niche that not many other tree species can.
It has the unique ability to grow in soils that experience both prolonged wetness and severe dryness. It flourishes in sunny open areas as well as more mixed and shady woodlands. This flexibility allows Oregon ash to occupy a range of river basin conditions. This is incredibly useful to conservation planners who have spent decades working to increase shade along the Tualatin River.
These same conservation planners are now reckoning with two compounding issues presented by EAB. The first is that an enormous amount of shade will disappear as Oregon ash trees die off. The second is the question of what species to plant in its place.
EAB is new to Oregon, but land managers in the Eastern United States have been grappling with its presence for twenty years.
Following invasive species infestations in other places informs our understanding of how similar infestations will impact ecosystems here. Biodiversity creates more resilient ecosystems. When a tree species is lost in a forest with high diversity, there is often another native tree that can fill the gap, therefore reducing the loss of ecological functionEcological Function The living and nonliving processes within an ecosystem..
In the Willamette Valley, where forested wetlands are almost entirely composed of Oregon ash, an EAB infestation will drastically transform the ecosystem. Because of Oregon ash’s specialized niche, it is unlikely that other native trees would adequately replace it. Instead, it is more likely that invasive plants would become established. This presents another layer of complexity.
In anticipation of EAB’s arrival, conservation practitioners in the Tualatin River watershed have scaled back the use of Oregon ash.
Now that the insect has been discovered in our close quarters, the conservation community is reimagining what environmental protection should look like. EAB is one indication of the far-reaching changes to come as our planet progresses further into an age shaped by global trade and a rapidly changing climate. The strategies that have been traditionally employed may no longer achieve long term objectives.
What species should we prioritize in this work? What is our relationship with non-native but benign plants? Should we continue to use local seeds or would seeds from a hotter, drier climate have better long-term outcomes? How can we cost-effectively support biodiversityBiodiversity The variety of species present.? These are some of the questions being asked as conservationists brace for an unknowable future.
Oregon ash may not be the prettiest tree in the forest but its contributions to water quality, soil health, and wildlife habitat are immense.
All native species, no matter how messy or intrusive, are valuable members of their community and are worthy of our gratitude.
As Dr. Bern Sweeney, Distinguished Research Scientist at the Shroud Water Research Center wrote, “The destruction caused by the emerald ash borer is a wake-up call that we ought to value each and every species in our forest and avoid any and all carelessness that might lead to the demise of any given species. For the loss of each species in a forest is analogous to death by a thousand cuts for the ecosystem.”