Assessing the biodiversity, threat status and protection levels of Africa’s rivers using geospatial methods

Abstract

African river ecosystems are crucial for biodiversity conservation, yet there is a significant knowledge gap in assessing their distribution, ecological condition, and protection levels at a continental scale in alignment with the Global Biodiversity Framework (GBF) targets. To enable reporting on Targets 1 (degradation), 2 (restoration), and 3 (protection) to the GBF it is important to assess these at a continental scale, because of the decline in biodiversity in Africa’s rivers due to various anthropogenic pressures. A continental assessment of river ecosystem types (RETs) has not yet been done for Africa. This dissertation aims to evaluate the extent of African river biodiversity types for reporting to Targets 1-3 of the GBF using freely available geospatial datasets and geospatial methods. Firstly, a variety of regional river lines and their associated attribute information were sourced and combined to classify the rivers based on Global Ecosystem Typology at the third or Ecosystem Functional Group. This allowed for the calculation of the African River Ecosystem Types (ARETs). Secondly, the 30-percentile threshold was used to determine the range-restricted ARETs. Thirdly, the ARETs were overlaid with the European Space Agency’s (ESA) land cover data at a 10 m spatial resolution dataset in the Digital Earth Africa platform. The study used categories of transformation based on the GBF, namely, high transformed (≥30%), moderate transformed (≥15%<30%), and low transformed (≥0%<15%). The river ecosystem types were intersected with dams to assess river fragmentation. Lastly, the ARETs were overlaid with the World Database on Protected Areas (WDPA) to determine the extent of their protection in meeting the 30% of Target 3 by 2030. The assessment used the protection level categories formulated based on the GBF, namely, well protection (≥30%), protected (≥15%<30%), and not protected (≥0%<15%). The number of RETs meeting the GBF protection level category is reported. The total extent of ARETs amounts to 6 442 613.9 km, with ecoregions, flows, and LGZs typology producing 123 coarser-scale (using the MHTs) and 823 finer-scale (using the FEOWs) ARETs. Among these, 37 MHT-ARETs and 241 FEOW-ARETS are found to be range-restricted. Results on the MHT-ARETS show that only 7 524 km (<1% of the total ARETs) are classified as highly transformed. The highly fragmented MHT-ARETs amount to 15 984.4 km (<0.2% of the total ARETs). Finally, the results on the protection levels show that 15 (12% of the MHT-ARETs) are considered well protected, leaving 88% inadequately protected. This highlights that current protection levels fall short of meeting GBF Target 3 and additional river length would need to be added by 2030 to achieve this goal