Fragmentation of family-owned farms and ranches has been identified as the greatest single threat to wildlife habitat, water supply, and the long-term viability of agriculture in Texas. However, an integrative framework for insights into the pathways of land use change has been lacking. The specific objectives of the study are to test the hypotheses that the nonagricultural value (NAV) of rural land is a reliable indicator of trends in land fragmentation and that NAV in Texas is spatially correlated with population density, and to explore the idea that recent changes in property size patterns are better represented by a categorical model than by one that reflects incremental changes. We propose that the State-and-Transition model, developed to describe the dynamics of semi-arid ecosystems, provides an appropriate conceptual framework for characterizing categorical shifts in rural property patterns. Results suggest that changes in population density are spatially correlated with NAV and farm size, and that rural property size is spatially correlated with changes in NAV. With increasing NAV, the proportion of large properties tends to decrease while the area represented by small properties tends to increase. Although a correlation exists between NAV and population density, it is the trend in NAV that appears to be a stronger predictor of land fragmentation. The empirical relationships established herein, viewed within the conceptual framework of the State-and-Transition model, can provide a useful tool for evaluating land use policies for maintaining critical ecosystem services delivered from privately owned land in private land states, such as Texas.

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This paper presents the results of an ecological field study of coastal habitats occupied by juvenile fishes, conducted from June 1979 to May 1980 in a segment of coast between Punta Gloria, SE of the city of Santa Marta and the Isla de Salamanca in the Caribbean coast of Colombia. Four habitat types were studied: very shallow marine shores, coastal lagoons (Punta Gloria and Costa Verde) and a estuary mouth (Ciénaga Grande); their ecological characteristics are described. Abiotic factors studied were surface water salinity and temperature, of which relationship with climatic and hidrological regimes is discussed. Adittionaly, changes in habitat size shape are described. A systematic list of collected fish species is presented, and an estimation of juvenile fish relative abundance per biotope is made and analysed in relation to abiotic factors.