Global dynamics of wildland urban interfaces: hotspots of hazards, services, and conservation

With the rapid growth of urbanization, there is an even more rapid increase in areas where wildlands and urbanization are juxtaposed, wildland urban interfaces (WUI). Here we provide a global perspective on WUI distributions and their role on key urban sustainability dimensions including environmental risks, ecosystem services, and threats to biodiversity. We implemented a definition of WUI that includes both areas of human development adjacent to wildlands and wildlands adjacent to development at the global scale. While North America and Europe have the greatest extent of urbanization and WUI lands, the most rapid rate of WUI expansion is occurring in Africa. This expansion coincides with tropical biomes, which historically had limited extent of WUIs, that are now experiencing the most rapid increases in WUI extents. Fire hazards in WUIs vary among continents and biomes with the largest proportion of fires in the WUI occurring in Africa and in tropical semi-humid regions. Water availability within the WUI also varies among continents and biomes with the greatest proportion of availability occurring in Asia and temperate biomes. Regions of conservation concern are disproportionately located within WUIs, including nearly 50% of conservation hotspots in Asia and both temperate and tropical humid areas globally having more than 40% of conservation hotspots within the WUI. Through this global assessment, we showed large variation in WUI extent and rates of growth and that these areas are hotspots for hazards, ecosystem services, and conservation that have large regional and potentially earth system consequences.