Using the Landsat Archive for the Monitoring of Mediterranean Coastal Wetlands: Examples from the GlobWetland-II Project

Abstract

The monitoring and assessment of the status and trends of wetlands is of major concern for long-term biodiversity conservation initiatives. In particular, the coastal wetlands in the Mediterranean have undergone considerable land use and land cover changes in recent decades, by way of urban growth and increasing tourism infrastructure. A rise in sea level would result in a major ecological pressure for natural and human-made wetlands in deltas and coastal lagoons. Satellite observation techniques allow for an objective monitoring of the Earth on large scales. Aiming at the demonstration of the current capabilities of satellite Earth observation applications to support inventorying, monitoring, and assessment of wetland ecosystems, the GlobWetland-II project makes use of the 35 years of Landsat archives for a basic identification and delineation of wetlands during1975, 1990, and 2005. We present results of wetland identification and delineation mapping from 1975 to 2002, for the test sites of the Menderes Delta and Güllük Bay. Methodically, a decision tree approach is used integrating multi-temporal spectral (Landsat MSS, TM, ETM+) and topographic (SRTM) satellite-based indicators for the occurrence of wetlands. While comparing the spatial distribution of wetlands over 27 years, a remarkable decrease of natural wetlands became obvious, particularly at the expense of increasing agricultural land use, artificial areas, or dam constructions. The detected land change processes show the capabilities of satellite-based Earth observation time series. In particular, the potential of the freely available Landsat archives for the quantification of the status and trends of Mediterranean wetlands in the framework of the RAMSAR Convention on Wetlands is demonstrated.