Quick Look: The Impact of Climate Change on Wildfires in The PNW

Photo Credit: Scott Rupp

Climate change is on its way to turning the PNW’s relatively cool summers into hot dry California summers. 

According to a report published in 2016 by Climate Central, a non-profit scientific research organization, the Pacific Northwest is in for a fiery future.

Climate Central reported that the length of fire season across the Western U.S. has nearly doubled since 1970. They also reported that the average annual number of large fires (large = 1,000 acres or more) has more than tripled between the 1970s and the 2010s and is expected to get even worse.

Much like California, Oregon and Washington are expected to experience extreme heat, increasingly large and dangerous wildfires, and drought caused by climate change.

The number of dangerous heat advisory days experienced in Oregon and Washington are expected to nearly double by 2050. And by 2100 Oregon and Washington parks can expect to be 8-12 degrees Fahrenheit warmer than they were in 2016.  

Hotter temperatures are expected to compound drought and wildfire danger. 

Increasing the danger to firefighters, at risk homes, and forest ecology. 

According to Climate Central, rising temperatures will also lead to an increase in the severity of widespread summer drought. Oregon’s drought severity is expected to increase by approximately 50 percent by 2050. Which could dramatically impact forest and agricultural productivity.

Washington is expected to see more than a 300 percent increase in drought severity by 2050. 

Wildfires are expected to happen more frequently, last longer, and be harder to fight as temperatures sore, forest fuels dry, and snowpack decreases.

Which is bad news for 1.2 million Oregonians and 2.4 million Washingtonians that live in areas that have an elevated risk of wildfire. 

Summer air quality is also expected to decrease as the number of stagnant air days in Oregon and Washington has grown by 15+ days since 1973 and wildfire smoke is the cause of some of the worst air quality days seen in Oregon and Washington.

After the Burn; Effects of Climate Change on Post-Fire Forest Processes

Climate change will also affect post-fire forest regeneration.

Wet coniferous forests have very little trouble regrowing but hotter and drier forests- not so much. Climate change in the Columbia Basin, with lower snowpack, less rainfall, and hotter temperatures will lead to increased regeneration failure, and an even longer recovery period for forests devastated by fires.

Decreased water availability can be lethal to young trees and plants as well as fish and wildlife.

The University of Washington said in a report that the highest risk of regeneration failure will be in dry forest areas, such as low-elevation Ponderosa Pine forests and Oregon White Oak Woodlands, which are home to a variety of wildlife including deer and mountain lions. Ponderosa pines, while well adapted to the current climate, prefer warm, not hot temperatures and low moisture. But according to one study regeneration potential of Ponderosa forests will decrease by 67% by 2060.

The edges of dry forests will also begin to convert to grasslands and shrublands as temperatures and droughts increase.

Reburns

The University of Washington has also reported that the number of ‘reburns’ (forest fires in areas that have already previously burned) is also likely to increase due to increasing temperatures and drought. Second-growth forests may be made particularly vulnerable to re-burn, because of dense planting.

After a fire, changed conditions lead to plant and animal species turn over, which can then be compounded by reburns. Without intervention reburned dry forests are more likely to convert to grasslands and shrublands as temperatures and droughts increase.

Climate Smart Forest Management

A report by the University of Washington said that climate smart forest management tools such as reducing non-climatic stressors such as landscape fragmentation and invasive species, reducing forest density, controlled burns, and installing fuel breaks can help to adapt forest management for the changing climate and to increase forest resilience.

Although such methods can be adapted to deal with climate change, they do nothing to reverse climate change itself and scientists continue to warn the public that global warming is accelerating at a faster rate than previously projected by the Intergovernmental Panel on Climate Change (IPCC).