Loss of mangroves as a consequence of the anthropic interactions downstream a river basin

摘要

Mangrove lands are becoming livestock and agriculture systems generating a reduction in estuary areas and an increase in the sediments transported towards the sea. This situation is prevalent in Marismas Nacionales, estuary of the San Pedro-Mezquital River, Mexico. Using satellite imaging, the deforestation rate for both forest and mangrove, as well as the morphologic change of the river and its floodplain were estimated. Remote sensing techniques were applied to achieve an integrated analysis of land change. The loss of forest was around 30% from the 80's to the 90's, and was more severe and constant in the middle of the basin. In this area, results show that the sediment increase directly affects water bodies and mangroves downstream, showing a decrease of 30% and 20%, respectively. The main land change was the conversion into agricultural areas, which affected coastal lands with large changes in sediment size and quality. The latter is due to the residual amounts from the anthropogenic economicactivities which form great water-stable aggregates by modifying the mangroves soil characteristics. This change of soil properties is related to the loss of capability to maintain biotic communities, thus ecosystems die gradually. However, the ecosystem could recover with active human participation.