The Kruger National Park (KNP) and surrounding areas is a semi-arid ecosystem supporting high levels of biodiversity and also benefits from ecotourism that contribute substantially to the South African economy. In addition, areas surrounding KNP are occupied by rural communities who solely rely on natural resources for their daily sustenance or livelihoods – including food and energy security. The location of KNP is well placed in the savannah ecosystems: open canopy forests (about 50% or less tree cover) made of heterogeneous layers of grass and woody plants. As the largest biomes in sub-Saharan Africa, these ecosystems host a large proportion of the African population, generally the poorest communities who rely extensively on ecosystem services, e.g. fuel wood, timber, grazing resources and edible fruits.
The woody component or tree cover plays a key role in ecosystem functioning, impacting on the fire danger, rates of transpiration and biomass production, nutrient cycling, soil erosion, and water distribution, and more widely on food and energy security. Bush encroachment impacts negatively on available grass resource for herbivores including wildlife and livestock. On the other hand, about 90% of rural community relies on fuelwood as their main source of energy and livestock production as their mainstay for livelihood.
Grazing and browsing resources supporting wild fauna and livestock production are the main provisioning ecosystem services and ecotourism is the main cultural ecosystem service provided by the KNP and adjacent communal areas. These provisioning services are crucial to sustaining ecotourism and rural livelihoods in the region. However, grazing and browsing resources are threatened by phenomena such as bush encroachment, overgrazing, elephant impacts and poaching of large mammals.
The KNP has witnessed high levels of rhino poaching in recent years. Bush encroachment is affecting the availability and quality of forage for wildlife and livestock and overgrazing in the communal lands has resulted into highly levels of depletion of grazing resources in terms of quantity (as measured by biomass) and quality (leaf nitrogen concentrations). The latter factors influence the occurrence and population dynamics of animals at a particular point in time. At the same time mega herbivores such as elephants do have an impact on a reduction of large trees which are important for the preservation of some species (e.g. bird species).
The underlying factors influencing the savanna landscape and the vegetation productivity are edaphic (soil and topography), climatic (precipitation and temperature) and anthropogenic (e.g. fire, grazing, fuelwood collection) and biotic factors (e.g. elephant activities). The savanna ecosystem is regarded as one of the heterogeneous ecosystems – patchiness of grass nutrients, tree species driven by geological types and climatic variables. The quality and quantity of grazing and browsing resources are therefore key indicators to monitor in the savanna system to ensure their sustainability.