Issue 7

Growing Population Increases Fire Risk at the Wildland-Urban Interface

by Steve McNulty

Years ago, large blocks of forest land were owned by a single individual. However, as these land parcels were sold and resold, they were divided among more and more owners. Where once a single person may have owned 200 acres, now 400 people may each own half an acre. This change in the wildland-urban interface has significantly impacted how this land area is managed. Even if the forest is left physicially intact, it is no longer practical to harvest the timber or control fuel build-up through controlled burns. Therefore, the risk of wildfires impacting residential areas has been increasing for several decades as people move out of the cities and into the country.

The SRS Forest Inventory and Analysis (FIA) program has monitored forest location, age, size, and species composition for the United States since the 1930s. In recent years, this program has expanded to include over 30,000 forest plots that are re-measured once every 5 years.

Wildfire Threat Map produced by the SRS Southern Global Change unit

Data collected by the FIA program is very useful in determining how forests and forest fire risk are changing with changing demographics. In the eastern United States, the greatest risk of large wildfires occur in areas of highly fragmented forest with much urban encroachment, coupled with areas of high forest fuel loads. These two factors can be combined to produce a wildlandurban interface fire risk map such as shown below. In the southern United States, parts of Arkansas and Tennessee represent the areas with the best chance of large-scale wildfire occurrence. These areas are heavily forested, but also have a large number of people living out in the forest. In combination, these two factors make both fire fuel load and wildfire control challenging; continued population pressures are likely to further expand the area of high fire risk in the future.

For more information:

Steve McNulty at 919-515-9489 or smcnulty@fs.fed.us

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Steve McNulty leads the SRS Southern Global Change unit team in Raleigh, NC.