Wildfire Predictions for the Next Century

Three things you need to know:

—Large, uncontrolled wildfires have increased worldwide and especially in the western United States during the past forty years.

—In the next 100 years, climate change is projected to lead to even more large wildfires, though different regions of the planet will be affected more than others (and some may even see a decrease in wildfires).

—The costs of fire suppression in the United States can be well over $1 billion annually, and more fires may lead to even higher costs. 

A wildfire rages in Bitterroot, Montana in 2000. Photo by John McColgan, courtesy of NASA.

 The debrief:

Researchers from NASA’s Goddard Institute for Space Studies have recently modeled historical global wildfires and compared their models to the known record of wildfires during the past 1000 years. Because their computer models match fairly well with what is currently known of past fires, the researchers used the same models to predict fire activity in the next 100 years.

“Up until recently, there was too little data to go back in time and see what the global wildfire activity was,” explained climate modeler Drew Shindell, who coauthored the new study. Now, however, there is a lot more information available from the past, which can help improve how scientists make predictions about the future, he said.

The models project that as average temperatures around the planet increase due to increasing amounts of greenhouse gases in the atmosphere, the number of wildfires will also increase. More fires aren’t expected in all regions, however. At the local level, the amount of rainfall, the number of people living where forests meet residential communities (the so-called “wildland-urban interface”), and the abundance of plants available as fuel will influence how often wildfires are ignited and how large they can become. 

A good example of these regional differences can be seen in the wildfire predictions for the United States. The same computer modeling study found that in the eastern U.S., the climate is expected to get more humid and rainy as average temperatures rise, which should lead to an overall decrease in fires. Hotter temperatures in the West, however, are expected to bring drier conditions, which are expected to result in more wildfires.

On the other hand, some dry regions in the West are projected to become drier and more desert-like, with fewer plants, which will cut down on the likelihood of big fires. 

These new findings are available online from the Proceedings of the National Academies of Science.

Why this science matters:

This new study, which models future wildfires in the U.S. and across the globe, is one of the first to match its model to a long historical record of wildfires. There is still only limited information available about past fire activity around the world, which reduces the confidence with which scientists can accurately predict future wildfires, but this study nevertheless compares its model against the best information available to date.

More valuable than the projection that global wildfires will increase in the next 100 years is an understanding of how regional wildfire activity will change. This study offers a valuable forecast for wildfires in the U.S., especially that more fires are expected in the western states because drier conditions will accompany warmer temperatures. However, the trend of more climate-driven fires in the western U.S. has already been observed; there were more than six times as many fires in this region between 1987 and 2003 than there were from 1970 to 1986. Although no single fire can be firmly attributed to climate change, it now seems that regional climate changes in the western states will increase the frequency of fires in that area for decades to come.

The current trend of increasing fires in the western U.S. and the prediction that even more are expected in the next 100 years comes with a significant pricetag. The annual costs of fighting wildfires in the United States now typically top $1 billion, and with increasing development encroaching upon forested areas, those costs are likely to continue to rise…