Browsing by Author "Douwes, Errol."

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Bioprospecting the flora of southern Africa : optimising plant selections.
(2005) Douwes, Errol.; Edwards, Trevor John.; Crouch, Neil Robert.
Focused procedures which streamline and optimise plant prioritisation and selection in bioprospecting have the potential to save both time and resources. A variety of semiquantitative techniques were assessed for their ability to prioritise ethnomedicinal taxa in the Flora of Southern Africa (FSA) region. These techniques were subsequently expanded upon for application in plant selection for the Novel Drug Development Platform bioprospecting programme. Least squares regression analyses were used to test the hypothesis that ethnomedicinal plant use in southern Africa is strictly random, i.e. no order or family contains significantly more medicinal plants, than any other order or family. This hypothesis was falsified revealing several 'hot' plant orders. The distribution of southern African ethnomedicinal taxa was investigated, and revealed low ethnomedicinal plant usage in the Western Cape and Northern Cape. The historical settlement of Bantu tribes in the eastern regions of southern Africa was one explanation for this discrepancy. Growth forms of ethnomedicinal taxa in 'hot' orders (identified in the regression analysis) were analysed. The results indicated no clear preferences across orders, but rather a preference for particular growth forms in certain orders. With respect to distribution, endemism and Red Data List status of ethnomedicinal taxa, the Western Cape had the greatest proportion of endemics and Namibia had the highest proportion of Red Data Listed ethnomedicinal taxa. With respect to chemotaxonomy, the Asteraceae contained the highest proportion of terpenoids, the Rubiaceae the highest proportion of alkaloids and the Fabaceae the highest proportion of flavonoids. The predictive value of regression analyses was tested against an existing analysis of anti-malarials and the subsequent in vitro bioassays on Plasmodium falciparum. In particular, the ability of these analyses to identify plants with anti plasmodial IC50 values of [less than or equal to] 10 [micro]g/ml was assessed. Most species in 'hot' genera showed comparatively good antiplasmodial activities (IC50 [less than or equal to] 10 [micro]g/ml). Plant candidates were prioritised for screening anti-tuberculosis, anti-diabetes and immune-modulatory compounds, using a weighting system based on; their ethnomedicinal application, chemotaxonomic potential, frequency in ethnomedicinal trade, association with the relative disease, toxicity, Red Data status, indigenous or endemic status, and family selection in ethnomedicine (identified through regression analyses). Other taxa were short-listed due to their presence in biodiversity hotspots where few ethnomedicinal plant use records are documented, and still others were incorporated due to their taxonomic association with efficacious exotic allies. Statistical analyses of the weighting processes employed were not possible in the absence of screening results which are due only in December 2006. The legislation governing bioprospecting in South Africa is discussed and several recommendations are presented to minimise negative impacts on the industry.
Seeing the wood for the trees : an evaluation of the Buffelsdraai Landfill Community Reforestation Project.
(2016) Roy, Kathryn Elizabeth.; Kirkman, Kevin Peter.; Adie, Hylton Ralph.; Douwes, Errol.; Roberts, Debra Cynthia.
Cities, and African cities in particular, will need a suite of relevant tools and approaches to deal with the varied climate change-related threats that these cities will likely endure in the future. African cities will be most affected due to the challenges of underdevelopment and resource shortages and, therefore, must address the climate change challenge in a way that ensures meaningful developmental co-benefits and overall cost-effectiveness. Local level actions, such as ecosystem-based adaptation (EBA), and community-based adaptation (CBA), are both effective forms of adaptation for African cities. The City of Durban (eThekwini Municipality, South Africa), has embarked on a novel approach that combines both these tools, the community ecosystem-based adaptation (CEBA) concept, of which the Buffelsdraai Landfill Community Reforestation Project (BLCRP) is a powerful example. The BLCRP is restoring indigenous forest in the buffer zone surrounding the Buffelsdraai Regional Landfill Site. The project aims to sequester a proportion of CO2 emissions generated locally during the 2010 FIFA World Cup™, whilst also uplifting local impoverished communities and building functional ecological infrastructure. The need to build the resilience of the city to climate change, in the face of increased uncertainty and risk, is considered urgent by planners. Building functional ecological infrastructure, which includes indigenous forest ecosystems, can help bolster this resilience. Early detection in restoration projects, such as the BLCRP, can allow problems to be identified and rectified through adaptive management in the early stages of restoration. This approach will affect the success and cost effectiveness of the restoration project. The BLCRP is currently in the establishment phase, a time when enrichment planting is best evaluated. This study examines the extent to which the composition, measures of diversity, and functional traits of planted species at restoration sites, are comparable with a local forest reference site. After three to five years, restored sites show low similarity with the reference forest due to different species composition and low species diversity and richness. Functional richness is significantly lower in two of the Buffelsdraai sites. Additionally, few bird-dispersed species were planted at Buffelsdraai and the restoration sites are infested with invasive alien plants compared with the reference ecosystem site. Furthermore, planted tree densities at the restoration site were considerably lower than figures recommended for restoration projects. Given these findings, the BLCRP is unlikely to meet long-term goals. To address these project shortfalls, I propose a higher planting density and a rigorous process to select tree species for planting. This includes implementing the framework species method at Buffelsdraai, which has proven successful in various countries. The framework species method encompasses the planting of mixtures of early and late successional species to capture the site, establish a multi-layered canopy, modify the microclimate and diminish weed growth in the years immediately after plantings. Species planted will also attract animals that will further disperse seeds into the planted area. A desktop assessment of forty-eight tree species helped determine which species would be suitable for field-testing and for eventual planting as framework species at Buffelsdraai. These included tree species common to the vegetation type found at the reference ecosystem site. A total of 18 species were considered unacceptable and removed, leaving 30 species as candidates for future testing. Best performing species were Celtis africana, Ekebergia capensis, Ficus natalensis, Bridelia micrantha and Croton sylvaticus due to their ability to attract wildlife, grow fast and tall and remain resilient to climate change. Worst performing species were Eugenia natalitia, Dalbergia obovata, Millettia grandis, Allophylus natalensis and Baphia racemosa, all of which were rejected from further testing. Future steps, such as nursery- and field-testing of candidate species, are recommended. The framework species method can be integrated with the current restoration method at Buffelsdraai. These recommendations will enhance biodiversity, increase canopy closure and reduce site management costs. Critically, appropriate and continuous monitoring is required to initiate appropriate management responses.