These forests of Cascadia are no stranger to heat, but the heat dome of 2021 was a uniquely rare and extreme event brought on by various climate-driven factors, that many tree species in the region are simply not able to withstand. Many trees died off as a result, which was initially chalked up to drought…yet further research found that this extreme heat caused widespread foliar damage to the leaves that degraded their cellular structure and ability to photosynthesize at all, even in stands with ample water that were not impacted by drought.
A recent study examined the impact of this event on these forests, and found it to challenge our ideas of ecological resilience and adaptation, revealing the physiological limitations of these ecosystems that we haven’t been considering in our climate risk assessments.
Think of it basically like coral bleaching - but instead of happening in the oceans it’s happening on land - with the heat-driven collapse of the physiological functions of entire ecosystems, creating novel disturbance regimes that these forests have never encountered before. When these forests experience disturbances at this scale, their overall ecological function is diminished, which can contribute to a loss in biodiversity and further amplify climate-driven impacts like wildfire, drought and disease, creating more problems that snowball over time.
A lot of our predictions for how these ecosystems will adapt in a changing climate has been made based on assumptions about how they handle drought, but extreme heat events like this could throw all that out the window and create even more devastating ecological collapse, which ultimately, underscores the importance of not only working to increase forest resilience during these trying times, but the need for policy and broad societal efforts to constructively address the root causes of anthropogenic climate change that’s creating these deadly events in the first place.
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