The wildland-urban interface (WUI) is the area where human life and their infrastructure meet undeveloped wildlands and their vegetation. Similar in theory to an ecotone (a transition area between two biomes, e.g. a field and a forest), WUIs are often focal points for human-wildlife or human-environment conflicts. In a recent study, a group of researchers at the University of Wisconsin-Madison and USDA Forest Service created a detailed map of the WUI across the nation. They found that it covered over 700,000 km2 (9% of land area), and impacted nearly 45 million homes (39% of all residents). The eastern states had the highest percentage of WUI; for example, 72% of Connecticut was classified as WUI. California had the most WUI homes at 5.1 million.
Housing development and urban sprawl cause significant habitat damage and fragmentation, which in turn threatens wildlife populations. In some areas, this leads to a loss of natural predators and a subsequent population boom of other species such as rabbits, deer and/or prairie dogs. The rise in the numbers of these animals further strains resources as the excess populations overgraze. Overgrazing quickly depletes necessary food stocks leading to wide-spread famine when resources have been maxed. Overpopulation helps to harbor disease and some species can even become carriers of maladies that affect humans, such as the bubonic plague or tularemia. It is estimated that greater than 50% of all endangered and threatened species in the United States are negatively impacted by urbanization.
Another crucial issue associated with WUI are wildland fires. In 2003, nearly 4,200 homes were destroyed by wildfires, the majority in southern California. Due to the number of people who are drawn to build homes in or near heavily wooded areas, there has been legislation proposed to reduce fuel loads in our public forests. While this could help to slow down or steer the course of a fire, it is not a cure-all solution to preventing the loss of homes in the WUI. All contiguous 48 states have areas classified as WUI, but due to the disparity in forest types, fire risks are higher in certain regions of the country than others. The communities in southern California are dominated by chaparral populations with short fire-return intervals and are the most prone forests to wildfire; while the mesic hardwoods of New Hampshire are less likely to experience wildfire.
While wildfire is of great concern for numerous reasons, it also has ‘cleansing’ effects on the areas it clears. Aside from clearing out naturally-occurring debris, it also can eradicate insects and disease as well as stimulate new growth that provides essential nutrients to the habitants of the forest. This study also helped to assess the effects of urban sprawl on biodiversity and ecosystem health. Species loss can trigger a domino effect in the environment that leads to further decimation, disease and dispersal of native plants and animals. The more that humans encroach on naturally pristine areas, the more likely that area will eventually recede, naturally or by force of “progress.”
The researchers concluded that an extension of conservation efforts needs to be examined, and stronger steps needed to be taken to help maintain our protected areas. They believe that larger buffer zones need to be created to prevent any further habitat loss, especially when related to threatened or endangered species and their habitats. The Endangered Species Act created the concept of critical habitat to protect the areas needed for those under safeguard to thrive; and those areas and species should be given greater consideration according to this group of researchers.