Despite a diverse collection of laws, regulations, executive orders, and administrative rulings directed at wetland protection, wetland conversion continues to occur as a consequence of permitting systems, exemptions, mitigation, and enforcement problems. Between 1992 and 1997, just over 204,000 ha of palustrine and estuarine wetlands were lost in the United States with the greatest losses occurring in the South (59% of the national losses). If land-use policy and planning are to be efficient in conserving wetland habitats, it is important to identify, in a geographically explicit fashion, those areas where the risks of future wetland habitat conversion are highest. The scientists’ objective was to predict the probability of wetland loss based on local characteristics of the wetland itself (e.g., type of wetland) as well as the wetland’s landscape context (e.g., surrounding land uses).
Because the South is home to nearly half the wetlands occurring in the coterminous U.S., and the region where the majority of wetlands were converted during the 1990s, the scientists focused their analysis of wetland conversion risk across the South. They used data from the National Resources Inventory (NRI) to identify inventory points that were classified as wetland habitat in 1992 and that, by 1997, either remained wetland or were converted to a non-wetland status. Wetland fate (retained or converted) was thought to be influenced by both local and landscape-level processes. For this reason, they defined two sets of predictors; local predictors that were derived directly from the NRI point inventory; and landscape predictors derived from the 1992 National Land Cover Data that was based on remotely sensed imagery to characterized land use and land cover in the vicinity of wetland points. A flexible and innovative statistical modeling approach (multivariate adaptive regression splines) was used to relate wetland fate to local features of the wetland and characteristics of the surrounding landscape.
Because conservation resources are scarce, it is essential to focus conservation efforts where the risks for further wetland habitat loss are greatest. The scientists’ model of conversion risk can be used to inform protection efforts by helping to prioritize wetland areas for conservation. Wetland habitats with high conservation value, high conversion risk, and low prediction errors would receive the highest priority for acquisition or other forms of long-term protection.