Doctoral Degrees (Conservation Ecology and Entomology)

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Browsing Doctoral Degrees (Conservation Ecology and Entomology) by Subject "African Dragon-fly Biotic Index (ADBI)"

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    A practical tool for evaluating freshwater health and biodiversity across Africa
    (Stellenbosch : Stellenbosch University, 2018-12) Vorster, Carlien; Samways, Michael J.; Simaika, John Pascal Simaika; Dijkstra, Klaas-Douwe B.; Stellenbosch University. Faculty of AgriSciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: The diverse African freshwater ecosystems are being increasingly impacted by human activities. Biomonitoring tools are needed to address the level of impacts and success of mitigation. Here a biomonitoring tool, using an effective indicator group (Dragonflies: Odonata), is developed at the African continental scale, while using the South African Dragonfly Biotic Index (DBI) as a starting point. The DBI can be applied to both still and running waters, and is based on three sub-indices (geographical distribution, threat status, and habitat sensitivity) of each dragonfly species. Data on dragonflies has been collated through international effort into the Odonata Database of Africa, used here to develop a new index, the African Dragonfly Biotic Index (ADBI). As with the DBI, the ADBI uses the same first two sub-indices (distribution and threat status), but replaces habitat sensitivity with a species vulnerability sub-index. This is more appropriate for the continental level in view of the quality of data available. Careful data interrogation led to final selection of 604 African dragonfly species for development of the ADBI. While the South African DBI scores were calculated at a national level, the ADBI scores were determined at a continental scale, which necessitated some changes in the calculations of the ADBI scores. To determine exactly how the ADBI deviated from the DBI, these two biotic indices were compared using just the South African dragonfly species as a data sub-set. There was a strong correlation between the Red List threat status sub-index and final scores of the ADBI and DBI, while geographical distribution sub-index scores of the ADBI and DBI were only moderately correlated. The sub-index that contributed most to the deviation of the ADBI from the DBI, was the ADBI species vulnerability sub-index. Although appropriate for a continental scale assessment, the ADBI has shortcomings for national level assessments, where conservation policy and management takes place. This meant that the ADBI had to be translated for specific use in the different countries so as to develop national biomonitoring schemes (i.e. a national DBI). However, as the spatial database created for Africa’s dragonflies varies in quality and quantity, the countries are at various levels of national DBI development. Countries were categorized on their potential to develop national DBIs by determining the value of data coverage of each country. Of the 48 African countries (excluding South Africa, which already has a national DBI), there are 12 that are close to being able to implement national DBIs, while another 12 have insufficient data and are not currently able to implement national DBIs. The other 24 countries require much more basic data to instigate national DBIs. Bioassessments of freshwaters takes place at two levels: 1) within political borders, and 2) in biogeographical regions. However, what is expedient at the national level often does not match biogeographical categories (e.g. ecoregions). Hence, the continental-scale ADBI was investigated according to Africa’s terrestrial and freshwater ecoregions. There were no significant differences between assessments using terrestrial vs. freshwater ecoregions, although using terrestrial ecoregions gives a finer interpretation of freshwater condition.