Lake Oswego Tree Summit focuses on climate change effects on tree canopy
Driving down just about any street in Lake Oswego, it would be difficult not to notice clusters of trees adorned in their vibrant, fall coats. And especially on a sunny day like Saturday, Oct. 30, the colors might distract from the realities of the community's tree health.
Roughly 75 participants gathered virtually during the Oct. 30 Tree Summit, hosted by the Oswego Lake Watershed Council and the Lake Oswego Sustainability Network. During the event, community members learned about the effects climate change has had on the tree canopy — something people may not have once paid much attention to.
The event featured discussions around climate threats to the city's urban forest and ways residents could help manage the tree canopy and soil in the surrounding areas.
Christine Buhl, an entomologist at the Oregon Department of Forestry, was the keynote speaker on the theme "Sustaining Our Urban Forest: Resilience, Responsibility and Reciprocity in a Changing Climate."
Buhl primarily focused on recent events that negatively impacted the forests: the ice storm and wildfires, which have been increasing every year.
Buhl noted that Oregon has had wildfires in the past, which can also be a natural component of the forest's ecosystem, but unnatural circumstances are what can "scar" forests beyond repair. She said wildfires are emerging quicker and more frequently now, which is dangerous.
Buhl said over one million acres burned in Oregon this year and people should take protective measures to mitigate urban fires like creating a buffer around their home and removing dead needles from gutters during the summer.
Another aspect climate change has brought forward is continuous periods of hot droughts. The long periods of hot weather and inconsistent precipitation have caused stressful environments for trees.
"The trees did not have time to acclimate," said Buhl about the heat waves this year. "We saw trees being taken by surprise."
The 2021 heat wave severely impacted trees along roads, forest edges and the coast. Buhl said people won't know about tree mortality until next spring when trees begin to bud, because they are entering the dormancy stage now.
"We do know that growth is definitely going to be reduced in these trees; defenses are going to be reduced in these trees," Buhl said.
Drought-affected trees may appear thin and experience premature leaf drop and branch loss.
Buhl said it's important to shift the perspective and focus on what trees thrive where, and plant native trees which are adaptive to specific sites.
"Very rarely is there one agent that is stressing a tree and killing it," said Buhl, adding that if people plant the right species in the right spaces, remove struggling trees and reduce competition for moisture, it can help manage a thriving tree canopy.
Participants asked questions including how to balance watering trees with drought and water conservation concerns, if invasive plants like ivy harm soil health and whether certain trees with top dieback should be removed and replanted.
Buhl said it's important to protect and irrigate native trees and focus on what species can thrive with less moisture. For ivy, she didn't know the effects on soil health but said it harms most things and should be removed. If people notice trees dying at the top, she said they likely won't fall for some time, though anything can happen. Typically, if a tree experiences top kill at 50% or more, Buhl said people should think about removal and replacement.
Another community member asked if air pollution from gas-powered lawn equipment affected the trees. Buhl said it relates more to collective damage by running all equipment in terms of global warming and climate change.
"That's kind of a drop in the ocean," said Buhl, adding that everyone needs to get on board and be more responsible.
During the second portion of the meeting, attendees discussed how they could use the information presented to help address climate change issues.
They expressed the importance of being mindful about the locations where specific species thrive, as well as considering Lake Oswego's overall tree health. Others said banning gas-powered lawn equipment, educating the public and looking at ways to volunteer and get involved with the city's tree canopy were important.
The city then discussed the latest LiDAR scan — which measures the landscape every five years — of the city's tree canopy.
The city has been tracking the tree canopy since 2006 and looks at aerial imagery to assess the canopy and help implement strategies to promote the benefits the tree canopy provides.
Lake Oswego saw a 5% increase in overall canopy coverage from 2014 to 2019, despite the recent natural disasters that caused tree loss.
The city is working to update the state of the urban forest report which was last done in 2009 to see how the canopy has changed across the city. For more information, visit the city's planning department website and visit the Watershed Council's website for more information as well. The recording of the event will eventually be uploaded to the group's YouTube channel.
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