Residential expansion as a continental threat to US coastal ecosystems

Spatially extensive analysis of satellite, climate, and census data reveals human-environment interactions of regional or continental concern in the U nited States. A grid-based principal components analysis of Bureau of Censu s variables revealed two independent demographic phenomena, alpha-settlemen t reflecting traditional human settlement patterns and beta-settlement desc ribing relative population growth correlated with recent construction in no n-agricultural areas, notably in coastal, desert, and "recreational" counti es and around expanding metropolitan areas. Regression tree analysis showed that beta-settlement was differentially associated with five distinct comb inations of seasonality, summer heat or cool, intensity of agriculture, and extent of "barren" land. Beta-settlement was greatest in coastal and deser t areas, and coincided with national concentrations of threatened and endan gered species.