USA: Fires in paradise: Exposure growth and catastrophe risk in the wildland-urban interface

With much of the flat Central Valley already used for agriculture, new development in Butte favors the Sierra Nevada mountains to the east. New neighborhoods on the eastern edge of Chico approach the foothills; further up the mountain, new homes and businesses appear frequently in the forested towns of Paradise and Magalia. Since 1980, Butte County’s population has grown by 60 percent, outpacing the national average.

The animation below, showing the last 40 years of development and wildfire activity in Butte County, is instructive. Note the new development on the east side of Chico, and ongoing development in Paradise and Magalia — much of it in extremely high-risk areas, parts of which have burned three or four times in the last 20 years (even before the current fire).

As roughly half of the county’s land area is either grassland (on the hills) or forest (in the mountains), wildfires are nothing new here. What is new, however, is the way the wildland-urban interface (an area designated as highly prone to wildfires) has expanded, not only as Chico expands toward the Sierras, but also as the heavily forested mountain towns continue to grow. This increasing exposure in high-risk areas — combined with dry air, rising temperatures from a changing climate, and increased forest fuel loads as a result of past fire suppression — likely contributed to the Camp Fire’s unprecedented ferocity.