Jan Vlok

Ecosystem Services, Land-Cover Change, and Stakeholders: Finding a Sustainable Foothold for a Semiarid Biodiversity Hotspot

Land-cover change has been identified as one of the most important drivers of change in ecosystems and their services. However, information on the consequences of land cover change for ecosystem services and human well-being at local scales is largely absent. Where information does exist, the traditional methods used to collate and communicate this information represent a significant obstacle to sustainable ecosystem management. Embedding science in a social process and solving problems together with stakeholders are necessary elements in ensuring that new knowledge results in desired actions, behavior changes, and decisions. We have attempted to address this identified information gap, as well as the way information is gathered, by quantifying the local-scale consequences of land-cover change for ecosystem services in the Little Karoo region, a semiarid biodiversity hotspot in South Africa. Our work is part of a stakeholder-engaged process that aims to answer questions inspired by the beneficiaries and managers of ecosystem services. We mapped and quantified the potential supply of, and changes in, five ecosystem services: production of forage, carbon storage, erosion control, water flow regulation, and tourism. Our results demonstrated substantial (20%-50%) declines across ecosystem services as a result of land-cover change in the Little Karoo. We linked these changes in land-cover to the political and land-use history of the region. We found that the natural features that deliver the Little Karoos ecosystem services, similar to other semiarid regions, are not being managed in a way that recognizes their constraints and vulnerabilities. There is a resulting decline in ecosystem services, leading to an increase in unemployment and vulnerability to shocks, and narrowing future options. We have proposed a way forward for the region that includes immediate action and restoration, mechanisms to fund this action, the development of future economic activity including tourism and carbon markets, and new ways that the science-stakeholder partnership can foster these changes. Although we acknowledge the radical shifts required, we have highlighted the opportunities provided by the resilience and adaptation potential of semiarid regions, their biodiversity, and their inhabitants.

On the origin of southern African subtropical thicket vegetation

The origin and affinities of southern African subtropical thicket have been misunderstood and neglected. This formation was only recognised as a biome distinct from savanna and karoo in the mid 1990s. One hypothesis states that it is a young vegetation type, assembled from forest, savanna and karoo elements after Holocene climatic amelioration. Others have suggested an ancient history for thicket. Here we review fossil and phylogenetic data in order to provide a better assessment of the origins of thicket. Albeit patchy, the fossil data are suggestive of a Palaeogene origin for this formation. A review of molecular phylogenetic data of extant thicket lineages indicated three major patterns: (i) ancient Cretaceous elements, including Encephalartos and the Strelitziaceae, (ii) basally branching lineages — many of which dominate contemporary thicket — that evolved in the Eocene (e.g. in the Celastraceae, Sapindaceae, Didiereaceae, Crassulaceae: Cotyledonoideae), and (iii) lineages derived from adjacent biomes that diversified in thicket in association with Neogene climatic deterioration (e.g. Aizoaceae, Asteraceae). We provide a narrative account of the evolution of thicket, which concludes that it is an ancient formation, extending back at least to the Eocene and derived initially from elements in the forest formations that prevailed in Upper Cretaceous and early Palaeogene times. As a biome, thicket is not uniquely southern African, being part of a formation that was globally widespread in the Eocene and which is extant in many parts of the world. Future research on the origins of thicket should focus on providing dates for major dichotomies as a complement to the rapid emergence of molecular phylogenies, as well as data on the genetic variation in populations of taxa categorised as ancient or young, and widespread or range-restricted.

Mapping Grazing-Induced Degradation in a Semi-Arid Environment: A Rapid and Cost Effective Approach for Assessment and Monitoring

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.

Effect of land cover and ecosystem mapping on ecosystem-risk assessment in the Little Karoo, South Africa.

Extinction-risk assessments aim to identify biological diversity features threatened with extinction. Although largely developed at the species level, these assessments have recently been applied at the ecosystem level. In South Africa, national legislation provides for the listing and protection of threatened ecosystems. We assessed how land-cover mapping and the detail of ecosystem classification affected the results of risk assessments that were based on extent of habitat loss. We tested 3 ecosystem classifications and 4 land-cover data sets of the Little Karoo region, South Africa. Degraded land (in particular, overgrazed areas) was successfully mapped in just one of the land-cover data sets. From <3% to 25% of the Little Karoo was classified as threatened, depending on the land-cover data set and ecosystem classification applied. The full suite of threatened ecosystems on a fine-scale map was never completely represented within the spatial boundaries of a coarse-scale map of threatened ecosystems. Our assessments highlight the importance of land-degradation mapping for the listing of threatened ecosystems. On the basis of our results, we recommend that when budgets are constrained priority be given to generating more-detailed land-cover data sets rather than more-detailed ecosystem classifications for the assessment of threatened ecosystems.