Ruiz-Valentín, Idelfonso

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    Development and testing of a spatial tool for the assessment anthropogenic threats in coastal and marine habitats in Puerto Rico
    (2013) Ruiz-Valentín, Idelfonso; Appeldoorn, Richard S.; College of Arts and Sciences - Sciences; Pagan, Francisco E.; Armstrong, Roy A.; Valdés Pizzini, Manuel; Kubaryk, John M.; Department of Marine Sciences; Gilbes, Fernando
    Marine and coastal ecosystems are subject to a wide variety of stressors derived from anthropogenic activities. Because of the complexity of these threats and the difficulty in monitoring them in a synoptic manner, scientists and managers must generally rely on proxy approaches to model stressors in the assessment of habitat condition and threat levels. Most previously developed coastal and marine threat indices acknowledge that the use of socioeconomic variables would assist in defining threatened marine habitats. This study investigated the incorporation of anthropogenic stressors into a GIS databased and applied them to develop a spatially explicit index of stress for the coastal and marine environments in Puerto Rico. Spatial quantitative data were used to construct and map indices of several key threats, including an overall threat index, In this application, socio-economic data were combined with watershed characteristics and coastal forcing that impact stress level and distribution. Twelve variables were reduced to develop high-resolution (250x250 m) indices for four threats: i) turbidity, ii) eutrophication, iii) pollution and iv) overfishing. All variables were standardized on a scale of 0 = 1 and then reclassified on a scale of 1 to 5. Classification was conducted within ArcView using the natural breaks function. The spatial index was defined by using a hexagon grid, (2 km2 or 898.6 m on a side), Means threats were merged within a grid cell, which resulted in 10,828 marine planning units for the region. Individual threat indices were combined to produce the overall index. Several problems were encountered in assessing anthropogenic stress using socio-economic vulnerability indicators due to the inherent difficulties involved in ranking socio-economic data on an interval scale. Temporal aspects also caused difficulties as socio-economic variables vary over time as coastal populations and land use change. Validation of results was assessed by comparing area-specific scores to field studies; these correlated well with expected outcomes. Cumulative threats generally were higher along the west and south provinces in comparison to the east and north provinces, suggesting that management of reserve areas must occur at a larger spatial scale, as many of the anthropogenic stressors may occur on the scale of the coast. Results of the combined threat index were classified and interpreted using a triage approach relative the management of marine protected areas.