Wildland Urban Interface
According to the federal register of the United States, the wildland-urban interface (WUI) exists where humans and their development meet or
intermix with wildland fuel. 1 Places referred to as the
WUI include forests, grasslands, shrub lands, and other
natural areas. Currently, approximately 33 percent
of United States homes are located in the WUI and,
since 1990, 60 percent of new homes nationally have
been built in the WUI. There are many reasons for
WUI growth including population growth and shifts
from the eastern United States to a still-growing west
and south. 2 Baby boomers are retiring and moving to
small, more rural communities close to scenic natural
resources. ( 2) Moreover, the WUI provides easy access
to recreation, scenery, lower property cost, and privacy.
This growth comes at a cost to the environment
and to the firefighters who protect lives and property
in the WUI. Evaluation of more than 1. 5 million
government records of wildfires extinguished or
managed by state and federal agencies from 1992 to
2012 found that humans have caused 84 percent of
wildfires during that 21-year period. 3 Historically,
lightning was the primary cause of wildfires and the
season for wildfires was limited to summer. Human-related ignitions have nearly tripled the length of
wildfire season. Of all fires ignited by lightning,
78 percent occurred in the summer. In contrast,
human-ignited wildfires were more evenly distributed
throughout the year, with only 24 percent occurring
in the summer. ( 3)
FIRE AND THE ECOSYSTEM
Historically, fire has played an integral part of the
ecosystem in many North American wildland areas
by stimulating growth of trees and other plants. Low
fire burns off excess fuel, cleans out underbrush, and
allows wildlife to flourish. According to the United
States Forest Service (USFS), fire-dependent ecosys-
tems rely on fire to do the following:
• Regenerate woodlands and native plants.
• Reduce hazardous fuels.
• Minimize the spread of pests, insects, and disease.
• Improve habitat for threatened and endangered
• Recycle nutrients back to the soil.
• Promote the growth of trees, wildflowers, and
other native plants.
• Sequester carbon to produce energy.
Fire is a fundamental ecological component for
94 percent of wildlands across the United States.
( 2) Growth into the WUI during the 20th century
resulted in policy-driven fire suppression in these
fire-dependent ecosystems. 4 As a result, fire became
Grow Or Burn?
Understanding the paradox of fire exclusion in the WUI
Fire mitigation in the WUI is unique
because it requires a combined
approach to mitigation at all levels of
land management: local, state, tribal,
and federal. (Photo by Mike Legeros.)