Thompson M., Vlok J., Rouget M., Hoffman M.T., Balmford A., Cowling R.M.
GeoTerraImage, P.O. Box 295, Persequor TechnoPark, Pretoria 0020, South Africa; Department of Botany, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031, South Africa; Biodiversity Center, South African National Botanical Institute, Brumeria, Pretoria 0001, South Africa; Conservation Science Group, Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom; Leslie Hill Institute for Plant Conservation, Department of Botany, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
Thompson, M., GeoTerraImage, P.O. Box 295, Persequor TechnoPark, Pretoria 0020, South Africa; Vlok, J., Department of Botany, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031, South Africa; Rouget, M., Biodiversity Center, South African National Botanical Institute, Brumeria, Pretoria 0001, South Africa, Conservation Science Group, Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom; Hoffman, M.T., Leslie Hill Institute for Plant Conservation, Department of Botany, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Balmford, A., Conservation Science Group, Department of Zoology, University of Cambridge, Cambridge CB2 3EJ, United Kingdom; Cowling, R.M., Department of Botany, Nelson Mandela Metropolitan University, P.O. Box 77000, Port Elizabeth 6031, South Africa
Improved techniques for measuring and monitoring the state of biodiversity are required for reporting on national obligations to international and regional conservation institutions. Measuring the extent of grazing-related degradation in semi-arid ecosystems has proved difficult. Here we present an accurate and cost-effective method for doing this, and apply it in a South African semi-arid region that forms part of a globally significant biodiversity hotspot. We grouped structurally and functionally similar vegetation units, which were expert-mapped at the 1:50,000 scale, into four habitat types, and developed habitat-specific degradation models. We quantified degradation into three categories, using differences between dry and wet season values of the Normalized Difference Vegetation Index (NDVI) for the three succulent karoo habitats, and the difference between maximum and mean NDVI values for the subtropical thicket habitat. Field evaluation revealed an accuracy of 86%. Overall, degradation was high: 24% of the study area was modeled as severely degraded, and only 9% as intact. Levels of degradation were highest for bottomland habitats that were most exposed to grazing impacts. In sharp contrast to our methods, a widely used, broad-scale and snapshot assessment of land cover in South Africa was only 33% accurate, and it considerably underestimated the extent of severely degraded habitat in the study area. While our approach requires a multidisciplinary team, and in particular expert knowledge on the characteristics and spatial delimitation of vegetation types, it is repeatable, rapid, and relatively inexpensive. Consequently, it holds great promise for monitoring and evaluation programs in semi-arid ecosystems, in Africa, and beyond. © 2008 Springer Science+Business Media, LLC.
Cost-effective approaches; Cost-effective methods; Degradation models; Dry and wets; Evaluation programs; Expert knowledge; Field evaluations; Habitat types; Hot spots; Induced degradations; Land cover; Land degradation; Multi-disciplinary teams; Normalized difference vegetation indices; Semi-arid ecosystems; Semi-arid environments; Semi-arid regions; Sharp contrasts; South Africa; Spatial delimitations; Study areas; Vegetation types; Arid regions; Biodiversity; Cost effectiveness; Degradation; Landforms; Monitoring; Ocean habitats; Remote sensing; Vegetation; Ecosystems; biodiversity; cost-benefit analysis; environmental degradation; environmental impact assessment; environmental monitoring; grazing; mapping method; NDVI; remote sensing; semiarid region; vegetation type; Animal Husbandry; Animals; Animals, Domestic; Conservation of Natural Resources; Ecosystem; Environmental Monitoring; Geography; South Africa; Africa; Karoo; South Africa; Southern Africa; Sub-Saharan Africa