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Wetland vegetation groups were used to characterise the regional context within which wetlands occur based on the premise that wetlands in a particular vegetation group are likely to be more similar to one another than to wetlands in other vegetation groups. Broad vegetation groupings reflect differences in geology, soils and climate, which in turn affect the ecological characteristics and functionality of wetlands.

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Wetland vegetation groups were derived by grouping the 438 national vegetation types of South Africa, Lesotho and Swaziland (Muccina and Rutherford 2004) into groups thought to reflect the turnover of wetland biodiversity at a national level. The expert knowledge of regional wetland ecologists was used to do the grouping, deriving a map of 133 wetland vegetation types. Future research should focus on improving these groupings using cluster analysis of representative surveys across the country. For most of the SANBI vegetation types, this was a simple exercise of deciding which vegetation types belonged in which groups. However, there were a few vegetation types where the landscape context of individual vegetation type patches (represented as polygons in the GIS layer) had to be considered:

• The “Azonal” category of the SANBI vegetation map was not used in deriving wetland vegetation groups as it is inconsistently mapped across the country. Instead, the “Azonal” category was incorporated into whichever vegetation type was surrounding that “Azonal” polygon.

• The “Forest” category was incorporated into whichever vegetation type was surrounding that “Forest” polygon.

• Polygons in the SANBI vegetation map identified as “Northern KwaZulu-Natal Shrubland” that were surrounded by “Ithala Quartzite Sourveld” or “KwaZulu-Natal Highland Thornveld” were included in a different wetland vegetation group (Sub-Escarpment Grassland Group 2) than if they were surrounded by any other vegetation type (in which case, they were included in Sub-Escarpment Grassland Group 4).

Using these vegetation grouping rules, a map of 133 wetland vegetation groups was derived from the SANBI vegetation map. This was then used, in combination with the landform map, to classify wetland ecosystem types. An excel spreadsheet for the SA vegetation types corresponding to each wetland vegetation group is

provided with the shapefile (wetveg_groups_SAVegTypes.xlsx). This does not apply to the Azonal, Forest and Grassland categories mentioned above.

Available documentation:

Nel, J.L., Murray, K.M., Maherry, A.M., Petersen, C.P., Roux, D.J., Driver, A., Hill, L., Van Deventer, H., Funke, N., Swartz, E.R., Smith-Adao, L.B., Mbona, N., Downsborough, L. and Nienaber, S. (2011). Technical Report for the National Freshwater Ecosystem Priority Areas project. WRC Report No. K5/1801.

SANBI, 2010. Further Development of a Proposed National Wetland Classification System for South Africa. Primary Project Report. Prepared by the Freshwater Consulting Group (FCG) for the South African National Biodiversity Institute, SANBI, Pretoria.

SANS 1878

FGDC-STD-001-1998