Sustainability of coastal resource use in San Quintin, Mexico

San Quintin, Mexico, provides a useful site for integrated analyses of mate rial fluxes and socioeconomic constraints in a geographically isolated syst em. Natural resource utilization on the land is dominated by groundwater ex ploitation for cultivation of horticulture crops (primarily tomatoes). Irri gation exceeds water recharge minus export by a factor of 6. Resource utili zation in the bay is dominated by oyster culture; food for the oysters is p rovided by tidal exchange of bay and ocean water. Consideration of oyster r espiration and system respiration suggests that the present level of aquacu lture is about 40% of the sustainable level. A "physical unsustainability i ndex" (PhUI) was developed to measure the proportional departure of utiliza tion of the most limiting resource for sustainability: 6 on land; 0.4 in th e bay. Based on PhUI and measures of economic development, we conclude that aquaculture is more viable than agriculture.