A comprehensive synthesis has been lacking in the scientific literature despite climate change's obvious importance in altering wildfire in the region, according to the study's authors. Wildfire is both highly visible and destructive, making it a natural focus of concern as the climate changes. For managers, the need for comprehensive information on climate-wildfire linkages has never been higher, as more frequent and severe wildfire disrupts ecosystems, infrastructure, and communities throughout the region.
"As scientists, we have made a lot of progress in understanding climate change and wildfire, but we haven't always done a great job presenting it in a way that is useful for land managers," said John Abatzoglou, the study's lead author and an associate professor of geography in the College of the Environment at the University of Washington. "Our goal was to pull together the most relevant and timely information related to historical and projected wildfire activity and present it in a way that is directly applicable to those on the front lines of managing wildfire risk in the Pacific Northwest."
The comprehensive study finds:
Increased wildfire activity since the 1980s has been strongly associated with rising temperatures.
Climate change has had a profound effect on the timing of the wildfire season, causing earlier onset, longer duration, and greater overlap of fire seasons across the region.
In the future, rising temperatures and changes in precipitation patterns will substantially exacerbate wildfire risk over much of the Northwest, with large areas of eastern Oregon and Washington, eastern British Columbia, and the northern Rocky Mountains projected to have large increases in burned area.
At higher levels of future warming, the area burned may approximately double that of the current climate, assuming no changes in vegetation, suppression capabilities, or fuel management.
The most damaging wildfires in the historical record coincided with warm, dry years characterized by La Niña climate patterns in the Pacific Ocean, and future events of similar atmospheric conditions superimposed on anthropogenic climate change are expected to be more severe and widespread.
A warmer and drier climate will contribute to longer burn durations and less opportunity for fuel to recover, leading to type conversions in vegetation composition with important ecological consequences.
Human-caused climate change makes it challenging to prepare for and manage megafires, leading to a greater likelihood of catastrophic fire behavior.
The findings align with previous research suggesting climate models can simulate important historical fire events that occurred under natural climate conditions, implying that these models provide useful insights into how large wildfires might respond under future climate conditions.
"This assessment should help natural resource managers and policymakers better anticipate how large and severe wildfires might change over the coming decades, and make the necessary changes to policies, budgets, management strategies, and mitigation investments across both federal and private lands," Abatzoglou said.
The study builds upon an earlier 2018 synthesis of climate-wildfire linkages authored by Abatzoglou and colleagues. The new study has benefited from research published in the last four years, including several landmark studies from fire modeling and paleoclimate communities that have advanced our understanding of linkages between climate and wildfire behavior over multiple timescales.
The study included input from dozens of scientists, managers, and policymakers across the region. The authors highlighted several key uncertainties and priorities for future research and monitoring, including improved attribution of observed changes to climate change, better estimates of future wildfire behavior, more research on fire-climate-vegetation interactions, improved understanding of long-term fire-climate relationships, and improved monitoring and modeling of fire weather.
"While there are still some elements of how wildfire will respond to climate change that are uncertain, the large body of research to date leaves little doubt that human-caused climate change is a primary factor driving the observed increase in large wildfire activity in the Northwest," Abatzoglou said.
