Abstract
Savanna ecosystems are geographically extensive and both ecologically and economically important; they therefore require monitoring over large spatial extents. There are, in particular, large areas within southern Africa savanna ecosystems that lack consistent geospatial data on vegetation morphological properties, which is a prerequisite for biodiversity conservation and sustainable management of ecological resources. Given the challenges involved in distinguishing and mapping savanna vegetation assemblages using remote sensing, the objective of this study was to develop a vegetation morphology map for the largest protected area in Africa, the central Kalahari. Six vegetation morphology classes were developed and sample training/validation pixels were selected for each class by analyzing extensive in situ data on vegetation structural and functional properties, in combination with existing ancillary data and coarse scale land cover products. The classification feature set consisted of annual and intra annual matrices derived from 14 years of satellite-derived vegetation indices images, and final classification was achieved using an ensemble tree based classifier. All vegetation morphology classes were mapped with high accuracy and the overall classification accuracy was 91.9%. Besides filling the geospatial data gap for the central Kalahari area, this vegetation morphology map is expected to serve as a critical input to ecological studies focusing on habitat use by wildlife and the efficacy of game fencing, as well as contributing to sustainable ecosystem management in the central Kalahari.
Highlights
The African continent contains the highest number of protected areas in the world and a significant percentage of terrestrial area in many southern African countries is protected for biodiversity conservation [1,2]
As the woody cover density progressively decreases among different vegetation morphology types, the peak of Normalized Difference Vegetation Index (NDVI) amplitude decreases along with increasing standard deviation of annual NDVI
Differences are visible in the green up and senescence between different vegetation morphology types due to the significantly steep onset on greenness for herbaceous dominated vegetated morphology types compared to slower onset in woody dominated vegetation morphology areas
Summary
The African continent contains the highest number of protected areas in the world and a significant percentage of terrestrial area in many southern African countries is protected for biodiversity conservation [1,2]. The majority of the wildlife population in the central Kalahari is restricted to two protected areas, the Central Kalahari Game Reserve and the Khutse Game Reserve, that are surrounded by leased farms with considerable livestock or game populations [5,7]. This situation has resulted in increased human–wildlife conflict due to growing incidences where predators leave the fenced protected areas to prey on livestock [8] and are eventually killed by farmers who are compensated by the government for their killed livestock [4,6]. Similar human-wildlife conflicts have been reported in other countries throughout southern Africa [6]
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