Land changes significantly alter biodiversity and ecosystem services (BES), the benefits people obtain from ecosystems. It is important to accurately quantify the land changes in order to understand the implications of these changes in a tightly coupled social-ecological context. The San Antonio River Basin (SARB) is an ecologically diverse region in South Texas. The city of San Antonio is located within the basin and is the hub of the North American Free Trade Agreement (NAFTA).
First, I apply the benefit transfer method to estimate multi-scale changes in ecosystem service values using two sets of widely cited valuation coefficients. The valuation results indicate that ecosystem service values decreases substantially since the NAFTA was enacted in 1994. More importantly, the results from sensitivity analyses indicate that the high value placed on urban areas, substantially overestimated the ESV of urban land.
Second, I apply the spatially explicit ecosystem approach based on the ecological production function method and find the synergistic spatial associations between biodiversity, carbon storage, and sediment retention over time at multiple scales using the nonparametric correlation analysis. The hotspot and overlap analyses indicate the continued decline in the biodiversity and ecosystem functions. The rates of biodiversity loss and carbon storage degradation have accelerated since the implementation of NAFTA in 1994 and the environmental consequences are negatively related to the urban sprawl in the San Antonio region. The sensitivity analyses indicate that the provision of carbon stocks is the most sensitive to forest cover and significantly linked with biodiversity loss in the SARB.
Third, I examine the environmental inequity of land in Bexar County from the perspective of environmental justice. The results suggest the spatial socio-economic segregation in public health risks and disparities in the changes in biodiversity and ecosystem services. Finally, I synthesize my findings and contributions; I also propose several policy interventions to mitigate biodiversity loss and ecosystem degradation and to internalize the negative externalities of urban sprawl in the San Antonio region.
- Guneralp, Burak Assistant Professor