Balancing agricultural and ecological needs : biodiversity, land use and ecosystem services in the Koedoes River Catchment, Limpopo.

Abstract

A major topic in natural science research is land degradation and unwise land use resulting in biodiversity loss and impact negatively on ecosystem functioning. In addition, an increasing human population trend leads to food security concerns. Some commercial farmers are ideally placed on the interface between agricultural and natural systems to investigate these issues. In this thesis we investigate the quaternary catchment-scale biodiversity, land-use patterns and interactions between conservation, restoration and agricultural activities in an agriculturally productive valley. The 40,000ha Koedoes River Catchment in Limpopo Province produces high numbers of tomatoes, avocados and mangoes. Most of this catchment is managed by ZZ2, a farming conglomerate that practice an environmentally sensitive approach to commercial farming. In the first two chapters a fine-scale vegetation map is created for the catchment, accompanied by detailed descriptions of the eleven mapped vegetation units. Over a 1300m altitudinal range, three biomes, 49 red-listed plant species, fifteen protected tree species and more than 500 species of vascular plant are represented in the catchment. In a subsequent chapter, the catchment-wide land-use patterns were mapped and related to vegetation patterns. The most expansive vegetation type appears to be one of the most threatened because large areas have been converted to croplands, while one of the most biodiverse vegetation units is severely threatened by degradation and invasive plants. Using this information, in addition to stakeholder feedback regarding the relative supply and demand for ecosystem services, a map of high priority biodiversity, ecosystem services and agricultural use areas was created to serve as a strategic management tool for stakeholders and land managers. In the final chapter the fine-scale effects of land use practices on biodiversity and ecosystem functioning are investigated. Using invertebrate community data from three adjacent headwater sub-catchments, invertebrate diversity and downstream biological water quality (measured by SASS5) was related to upstream land use. Ultimately, this thesis serves to illustrate some of the complex interactions and inter-dependencies between conservation and agriculture, and to offer evidence for mutually beneficial synergies between both these important sectors.