The Okavango Delta is a hydrologically complex and dynamic ecosystem that changes within seasonal, yearly, and decadal time intervals. The amount of water reaching the Okavango River from highlands of Angola has a direct impact on spatio-temporal variation in inundation levels over the Delta. This results in a mosaic of ecologically defined landscape components such as permanent swamps, islands, floodplains and drylands. These landscape components have defined vegetation communities, particularly islands. The size of islands varies from anthill, covering some square meters to forest covered islands of several hundred square kilometres. The extent of tree cover is variable with some islands having a complete tree cover and others only narrow fringe close to the island edge with the centre of island either colonized by herbaceous species or devoid of any vegetation. Islands that are of interesting nature are those with a fringe of riparian vegetation adjacent to floodplains; island interior community dominated by Acacia nigrescens, Croton megalobotrys and Hyphaene ventricosa; central regions characterized either by short, sparse grassland dominated by Sporobolus spicatus or completely devoid of vegetation with sodium carbonate encrusted soil surrounding a central pan of extremely high conductivity. In these islands the highest amount of organic C and total N occur in riparian forests. If the temporary swamps of the Okavango Delta could become dry due to climate change, riparian forests in islands will die and grasses typical of those on island centres will become dominant resulting in reduced soil organic C and total N. There will also be increased salinity in the water of the Okavango Delta. Therefore, the different vegetation zones in the Okavango Delta, particularly riparian forests in islands influence the biogeochemical processes occurring there. It is important to maintain the vegetation zones in islands, especially riparian forests as important components of this ecosystem.

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