The Effects of Anthropogenic Stressors on Wetland Loss and Habitat Quality Deterioration in the Upper Guadiana River Basin: A Long-Term Assessment (1970–2000)

During the last four decades, around 1,500 km2 of dry croplands have been transformed, and are now irrigated in the Upper Guadiana river basin, causing hydrologic overexploitation and wetland desiccation. However, there are no estimations on how anthropogenic stressors have been changing the wetland landscape in the recent past. This chapter focuses on the understanding of how the changes on land-use land-cover (LULC), economic activities and population have driven wetland losses and habitat degradation in the basin from the 1970s. Our results show that 40.5% (2,041.6 ha) of the 5,321 ha of wetlands existing in the early 1970s had disappeared in the last 30 years (1970–2000). Most wetland losses occurred through the period 1978–1990, which registered a rate 127 ha of wetland lost per year. Most affected were floodplain wetlands (47% of total loss) and rain-fed temporary ponds (24%). During the entire period 1978–1999, the loss of wetlands could be significantly related to the loss of natural vegetation, as well as to the reduction of agricultural employment. Habitat quality of wetlands showed a clear pattern of nutrient over-enrichment, as well as a trend towards salinization, the later related to the greater disappearance of most freshwater wetlands (0–2,500 µS cm−1). LULC, economic activities and demography explained around 50% of wetland loss and habitat quality deterioration. Until 1990, the pressure of population growth, combined with the agricultural sector, explained the disappearance of most wetland area. From then on, habitat quality has been more impacted in areas where industry and building sectors had more weight in the socioeconomic development (also densely populated watersheds).