A spatial analysis of cumulative habitat loss in Southern California under the Clean Water Act Section 404 Program

Habitat loss is the leading cause of biodiversity reduction in the world today, with wetlands having experienced especially large losses in the United States and elsewhere. Using remote sensing and GIS techniques, this study quantified cumulative habitat loss in two Southern California watersheds associated with Clean Water Act Section 404 permits, primarily for developments, issued by the U.S. Army Corps of Engineers from 1984 to 2002. While the majority of habitat loss occurred outside of explicitly 404-authorized developments, non-explicitly authorized development represented a substantial fraction of observed habitat loss. The spatial distribution of habitat loss and 404 permits were analyzed statistically. In almost all cases, percent habitat loss was significantly correlated with variables representing 404 authorizations. These correlations may indicate the presence of incidental authorizations, suggesting that 404 authorizations within the study area may have indirectly facilitated nearby development (i.e., growth-inducing impacts). This study expanded the use of remote sensing, GIS, and spatial statistics for the purpose of regulatory-driven cumulative impact assessment. Until resource agencies quantify cumulative impacts in a spatially explicit manner and analyze those data statistically, there can be little rigorous scientific basis for formulating regulatory or policy decisions regarding cumulative impacts.