Changes in the macro-vegetation of the Kis-Balaton Wetlands over the last two centuries: a GIS perspective

Abstract

The Kis-Balaton Water Protection System (KBWPS) is a wetland restoration project of over 8000 ha in extent, established to protect the water quality of Hungary's Lake Balaton. The healthy survival of the wetland macro-vegetation is essential for processes of bio-filtration, thus regular vegetation surveys have been carried out since the project began, to monitor the macrophyte growth in correspondence with the re-flooding. This biomonitoring is now very sophisticated, using ortho-photographs and a GIS database. However, the processes of wetland survival and regeneration are not fully understood, nor are the timescales involved; but there does exist in Hungary much archive cartography, especially since the 1780s, as well as records of the water-levels of Lake Balaton and of wetland extent and condition, which could be of great value in managing the KBWPS. Archive maps contain much information about past environments and if viewed in a historical series, can depict environmental change and response in some detail. In the first part of our study we used the maps of the KBWPS area produced by the three Military Surveys of Austria-Hungary (1783–84, 1856–57, 1872–74) to quantify the changes in vegetation cover over the last two centuries. In the second part of our study, we produced a Digital Elevation Model of the area and applied overlays representing the range of values of water-level in the archive data: thus we produced a series of maps showing the extent of water-cover and its depth for each level. We compared these to our derived vegetation maps for the same periods and were thus able to make assumptions on the vegetation-cover of the past and how it changed.