This year’s unique heat dome left catastrophic impacts on forest canopy, according to a new study published in the journal Global Change Biology. This rare and dangerous extreme weather event hammered the Pacific Northwest in June of 2021. Research by Adam Sibley and his co-authors underscores the acute effect of mortality on forest canopy foliage in western Oregon and western Washington, which experienced the most intense record-breaking temperatures.
This heat dome phenomenon resulted in dangerously high temperatures throughout the region. Portland reached an eye-popping 116 degrees Fahrenheit, Salem, Oregon, 117 degrees, and Lytton, British Columbia, an astonishing 121 degrees. The sudden increase in temperature was shocking and proved to be severely damaging ecologically. Almost 5% of the forested area across these non-wilderness regions was burned.
Immediate Effects on Forest Canopy
Additionally, the study carefully tracked the short-term impacts of the Puget Sound heat dome on tree canopies. The results showed that leaves in these wooded landscapes fully matured one month earlier on average. Soon after exposure to extreme heat, healthy green leaves morphed into fiery red or orange shades. These quick changes are a sign of acute stress to the trees, especially among species proven to be sensitive to increased heat.
This research identified that species such as western redcedar, western hemlock, and Sitka spruce have cultural and economic significance. Unfortunately, these species were hit the hardest by the heat damage. These indicator species are essential to sustaining the health of our natural ecosystem. In addition, they spur local economies and deepen cultural traditions. Scientists were excited to find that 69% of the forest within Olympic National Park is flourishing with old-growth species. This dominance serves to underscore the long-term threat posed to this precious global ecosystem.
Geographic and Species-Specific Vulnerabilities
Altogether, the results revealed a number of geographic vulnerabilities, but none more strikingly than Washington’s Olympic Peninsula, where widespread foliar scorch was seen. Additionally, the region is home to Olympic National Park, an important area for biodiversity and conservation efforts. The report provides the most comprehensive estimates of damage to forest canopies. These findings are immensely valuable to land managers as they prepare for a new era of extreme heat.
Heat is a known killer of Douglas-fir trees. They’re threatened by a disease called Swiss needle cast, a fungal affliction that makes P. This multifaceted threat underscores the urgency for forest management strategies that consider not only immediate heat impacts but long-term resilience against climate change.
As tree physiologist Chris Still in the College of Forestry, one of the investigators on the new research, noted, this work can’t come soon enough. He made the case for everyone to understand what various tree species can do in response to extreme heat. This expertise is key to developing successful accountability-oriented management practices. For land managers, the study is a critically important tool. It allows them to address the issues caused by increasingly severe extreme heat and extreme cold.
Implications for Future Forest Management
With climate change driving more frequent and severe extreme weather, the consequences of this new research go far beyond initial damage estimates. With this context, paired data offers critical evidence that should inform proactive land management practices to reduce future hazards. By knowing which species are most vulnerable, managers can undertake preventive measures. Knowing how forest ecosystems are stressed by heat helps them be better equipped to weather future heat waves.
The study emphasizes an urgent need for advance adaptive management approaches that translate scientific knowledge into practice. Much of the national forests in western Oregon and Washington have been squandered. We need to start being much more proactive about protecting the long-term longevity and health of these wonderful ecosystems.