Assessing the distribution of wetlands over wet and dry periods and land-use change on the Maputaland Coastal Plain, north-eastern KwaZulu-Natal, South Africa

Althea Theresa Grundling, Elzie Catharina Van den Berg, Jonathan Stephen Price

Abstract


The Maputaland Coastal Plain (north-eastern KwaZulu-Natal) hosts an array of wetlands that provide valuable ecosystem services to an increasing population and tourism demand. The apparent distribution of wetlands varies in response to periods of water surplus or drought, and over the long-term has been reduced by resource (e.g. agriculture, forestry) and infrastructure (e.g. urbanisation) development. This study used Landsat TM and ETM imagery acquired for 1992 and 2008 (dry) and Landsat ETM for 2000 (wet) along with ancillary data to 1) identify and map permanent and temporary (inland) wetlands and open water based on their spatial extent and distribution during wet and dry years; and 2) determine wetland loss from land-use changes due to cultivation, plantation and urbanisation using imagery between 1992 and 2008. In 1992 (dry) the smaller wetland extent primarily identified “permanent” groundwater-fed wetland systems, whereas for the wet year (2000) both “temporary” and “permanent” wetlands were indicated. Comparison between both dry years (1992 and 2008) indicates an 11% decrease in wetland (sedge/moist grassland) and a 7% increase in grassland distribution over time. Some areas that appear to be grassland in the dry years are actually wetland, based on the larger wetland extent (16%) in 2000. Swamp forest wetlands were difficult to map and needed the support of ancillary data. Minor expansion of urban areas (0.87%) and the change in plantation and cropland distribution also replaced some wetlands. The 2008 Landsat TM dataset classification for the entire Maputaland Coastal Plain gave an overall 80% mapping accuracy.


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