The Pacific Northwest Heatwave!

06 Jul The Pacific Northwest Heatwave!

From June 25th through June 29th the Pacific Northwest (PNW) experienced record-breaking temperatures due to a heatwave. A heatwave is caused when a high pressure system settles over a region. Air is forced downwards and does not allow warm air to rise and so the trapped air only gets hotter. In Seattle, temperatures passed 100 degrees Fahrenheit for three consecutive days (06/26 -06/28) with Monday the 28th breaking the record for highest temperature recorded in the city at 106 degrees. On June 28th in Portland, Oregon the temperature rose to 113 degrees, and in Salem, Oregon the temperature rose to 117 degrees! Here at the Ranger Station in Marblemount, Washington, the temperature was over 100 for most of the weekend and the hottest on Monday at 107 degrees. While these temperatures might be common for some states such as those that are located in the southwest, they are extremely uncommon in the PNW. For some context, Seattle had only recorded temperatures over 100 degrees 3 times before this heatwave.

Aside from being a bit uncomfortable, these uncommon temperatures have major impacts for the park. Snow is melting more rapidly at the higher elevations and this presents challenges for the already delicate alpine environment. Also, certain areas within the park dry out and increase the risk for fire. Plants both at the higher and lower elevations of the park struggle to cope with the extreme change in temperature. When the leaves of plants are exposed to extreme heat, they can become stressed or scorched as they are not able to keep up with water that is lost through transpiration. Plants can generally recover when temperatures return to normal conditions, but in extreme or prolonged cases, the plant becomes susceptible to pests or diseases or dries out. Younger plants are even more susceptible to impacts from extreme heat.

Photo: Scorched leaves on a Bigleaf Maple (Acer macrophyllum) sapling

Since the majority of the plants at our nursery are just starting out, they required more attention during this time. We had to increase the frequency of watering to account for the heat and check on soil moisture more frequently as well. Some plants dry out quicker than others, so this is something else that had to be accounted for. Still, there were some plants that just could not endure the heat.

Photo: Scorched Partridgefoot (Luetkea pectinata)

Unfortunately, it seems that these types of extreme weather events will become more frequent as we look toward the future. Heatwaves have occurred before but climate models show that their severity has only increased due to warming caused by climate change. The rate at which the planet is warming presents challenges for the majority of plant species in the PNW as well as other parts of the globe. Some plants at higher elevations can move up to escape the effects of climate change, but that seems unlikely when considering the current rate of change. More than likely plants at higher elevation will see their range shrink, but this also means that potentially plants at lower elevations could see their range expand. This is a very complex situation we face and does raise questions for the future of native plant restoration, but I am very interested to see what can be done to overcome these challenges!