Photo Credit: Where to build/re-build post wildfire is an important piece to the wildfire mitigation puzzle. Photo by Kari Greer via Flickr Creative Commons

Structures exist in the wildland-urban interface (WUI); that’s what makes it a WUI and not just a wildland. Recent research shows, however, that the WUI gains even more structures post fire. Credit: Boise National Forest

For plants, the ability to resprout is an age-old signature of fire. Some of my favorite trees, shrubs and grasses are resprouters: oaks, redwoods, manzanita, hazel, California fescue—it’s a long list. When I drive through burned areas, I follow dead trees and shrubs to their bases, looking for that tell-tale sign of life after fire: the fresh shoots, the green leaves, the next iteration. So whenever I drive over Oregon Mountain in Trinity County, California, near where I grew up, I get caught up not in the starkness of an area that’s burned four times in the last 15 years, but in the proliferation of oaks and redbud and downright beauty that’s followed those fires. I see Oregon white oak sprouts that are 10 feet tall, surrounded by dead conifers that had been shading out the oaks before the fires, and I relish in the competitive power of the resprout. But last month, driving over that very mountain with Emily Troisi, she commented on something else that seems to be regrowing there post fire: houses.

A rebuilt home in the footprint of the 2001 Oregon Fire near Weaverville, CA. Credit: Download from Google Street View.

During the 2001 Oregon Fire, 12 buildings burned on the outskirts of Weaverville, and since then, many houses have been rebuilt. It’s hard to imagine wanting to rebuild in that area—a south-facing slope in a Mediterranean climate where summer temperatures often exceed 100 degrees Fahrenheit, which is now covered with post-fire regrowth, has a major highway (i.e., ignition source) running through it and has seen three more wildfires since 2001. Yet, it’s a beautiful location, close to town but not in town, with views of the Trinity Alps and other local mountains. And for the people who live there, it’s home.

Last week I came across a paper in the International Journal of Wildland Fire, and it brought me back to Oregon Mountain. The paper, published last year by Patricia Alexandre at the University of Wisconsin and her colleagues in Oregon and Colorado, looks at rebuilding patterns and new housing development after wildfire. A quick scan of the abstract told me what I was hoping wouldn’t be true: in wildfire footprints across the country, more buildings were present five years after fire than before those areas had burned. And guess which region had the highest rebuilding and new development rates within fire perimeters? Yep, my beloved California.

Figure 3 from Alexandre et al. 2015 provides summary data for fires that occurred in the continental US between 2000 and 2005. Credit: Alexandre et al. 2015

The authors took on a monumental task, identifying all burned and rebuilt buildings within fire footprints across the conterminous United States for the years 2000-2005—a time period that includes the housing boom. They used the Monitoring Trends in Burn Severity dataset to determine fire perimeters, then used Google Earth imagery to identify and tally buildings within those footprints both pre and post fire. Overall, the authors analyzed 2,318 fires, 40 percent of which contained buildings, but only 11 percent of which had buildings that burned to the ground. From 2000-2005, an average of 5.9 percent of buildings within fire perimeters burned. Rebuilding rates varied greatly from year to year, ranging from 6.2 percent in 2000 to 63.8 percent in 2003 and averaging 25.3 percent over the study period. New building construction exceeded rebuilding every year; a total of 1,881 burned buildings were rebuilt, whereas 2,403 entirely new buildings were constructed within fire perimeters during the same period.

It’s interesting to note that rebuilding rates were relatively low; a majority of individual property owners chose not to rebuild the structures that they lost. However, rates of new development within fire footprints were higher, and ironically, this was especially true in areas with highly flammable vegetation and frequent fire regimes, like the Mediterranean parts of California. It makes me wonder: Do these patterns suggest a certain level of pragmatism on the part of local residents, which is unparalleled by developers? Or do they reflect a complicated matrix of financial incentives, insurance arrangements and population pressures, which may favor new development over rebuilding?

Figure 1 from Alexandre et al. 2015 shows an example of a building rebuilt after a 2003 fire in Colorado. From left to right: 2000, 2003, 2005. Credit: Alexandre et al. 2015

As a plant nerd, I celebrate resprouting as the quintessential fire adaptation—a competitive edge for plants in fire-prone environments. Yet for human communities, the decision to rebuild and regrow in the footprint of a fire is not so straightforward, and fire adaptation likely means changing course in some way, whether it’s walking away from a specific site, using different building materials or otherwise modifying the arrangement of buildings and fuels on the landscape. I find this paper to be an important reflection point for communities, policy makers and developers, as fire is becoming increasingly relevant to our decisions about how we design and construct our communities. Unlike trees and shrubs, whose post-fire decisions are hardwired, automatic and not always favorable, we have the luxury (and burden) of being able to actively adapt to fire with information and intention. Let’s use it!

Reference:

Alexandre, P.M., Mockrin, M.H., Stewart, S.I., Hammer, R.B. and Radeloff, V.C., 2015. Rebuilding and new housing development after wildfire. International Journal of Wildland Fire, 24(1), pp.138-149.

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