Monitoring indicators for Mediterranean wetland and agricultural area using ALOS data
Thomas Alexandridis(1), Agamemnon Andrianopoulos(1), Vasileios Takavakoglou(1), George Zalidis(1), Charalampos Topaloglou(1), Nikolaos Silleos(1), Ioakeim Pardalis(1), George Tsakoumis(1) and Moschos Vogiatzis(1)
(1) Aristotle University of Thessaloniki, University Box 259, University Campus, 54124 Thessaloniki, Greece
Agricultural and other human activities are a pressure to several Mediterranean wetland ecosystems. Monitoring the pressures and the state of the ecosystem is an important input to management activities. The aim of this work was to select and implement indicators for monitoring the natural and agricultural environment of a Mediterranean wetland using Earth Observation (EO), and specifically the recently launched ALOS satellite images. Specific objectives included: (i) integration of multiple levels of data, (ii) selection of the monitoring indicators, and (iii) application of the methodology in the study area (Ramsar site "lakes Koronia-Volvi", Greece).
Multiple levels of data were collected and integrated: remote sensing data (ALOS AVNIR-2 and PALSAR), unmanned aerial vehicle (UAV) images, and observations during field surveys. EO and GIS methods used during monitoring of the study area involved pre-processing of the satellite images, enhancement of information, information extraction, and derivation of indicators. More specifically, the ALOS AVNIR-2 image was used in spectral classification of land cover in the basin level, to update the Natura 2000 habitat map, and delineate the extents of surface water bodies. The ALOS PALSAR image was used to identify the inundated vegetation, an important wetland habitat. The combined extents of water surface during high and low water level defined the wetland's hydroperiod. Geographic overlay comparison with results derived from the area in 2003 using ASTER and Landsat images was used to identify the changes that occurred during the last years.
Resulting thematic maps revealed and quantified the intensity of pressures in the vicinity of the protected wetland: intensive irrigated crops covered 25% of the agricultural area, and water abstraction from the aquifer had the highest intensity around the main feeders of the lakes. The state of the wetland was described with the seasonal change in the spatial extents of the water bodies, and the spatial distribution of habitats (Annex I of Habitat Directive). Study of the changes that occurred during the last four years (2003-2007), revealed that irrigated agriculture did not increase significantly, but settlements have expanded. The most notable change in the state of the wetland was a reduction of open water extent in lake Koronia followed by an expansion of the reedbed and tamarisks.
Concluding, the ALOS imagery was successfully integrated with other datasets to derive monitoring indicators, it was comparable with work already performed with other commercial satellite images (ASTER, Landsat), and is thus suggested for use in natural and agricultural monitoring and management plans. ALOS data were provided by the European Space Agency (ESA). The work presented was supported by the WETMUST project (Ιntegrated multiple level wetlands monitoring system using innovative technologies, INTERREG IIIB ARCHIMED), and the application of ESA's GlobWetland project in Greece.