Is it really possible to restore degraded grazing lands?
South Africa is a very dry country, 94 per cent of which is classified as hyper-, arid and semi-arid with less than 650 mm/a of rainfall.
Land degradation
Although mismanagement often leads to the degradation of grazing land (rangelands), many other factors cause a decline in the functioning and structure of natural resources, especially the vegetation and soil. Among these are climatic impact, like drought, or thickening woody species (shrubs and trees) in especially savanna regions (a mixture of grasses and trees), also known as “bush encroachment”.
A decline in the vegetation cover is mainly caused by the competition for moisture in the upper soil layers. Bare patches are then recognised in the landscape or where the grass sward is depleted, the shrubs become denser, leading to a decline in the grazing capacity of the rangelands.
Restoration ecology
It is, therefore, important to restore the moisture and contribute to the enrichment of the nutrient levels of the degraded soils. The restoration also contributes to higher biodiversity and increases the food and water security for a wealthier population. Restoration includes aspects like rehabilitation, reclam-ation, re-vegetation, reinforcement, etc. The terminology differs according to the rate and level of restoration that is implemented to reach a certain structure and function in a specific environment or practice implemented. According to the Society of Ecological Restoration (SER), “ecological restoration can be defined by the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed.” Restoration methods must be monitored over the long-term to determine the increase in vegetation cover that could lead to an improved grazing capacity.
What do we do?
Scientists from the terrestrial ecology research group at the North-West University are testing several restoration methods in the more arid and semi-arid western parts of South Africa.
The main aim is to restore the moisture and nutrient levels of the soils for increased grass biomass production that lead to better grazing for livestock production. Many different experiments are carried out in areas that are commercially or communally managed in the grass and savanna ecological systems.
Restoration methods
In areas that are characterised by bare patches with little or no grass, the soil surface is loosened by a mechanical implement. If the soil seed bank is depleted, seeds of perennial, good grazing grasses are re-seeded. In savanna areas, where bush encroachment occurs, the woody trees and shrubs are con-trolled by chemical (aerial spraying in photo 1), manual, mechanical or biological (e.g. fire) methods. The branches and twigs of the trees and shrubs are then used to cover the bare and eroded patches (so-called “brush packing”) that will control further grazing by animals.
The branches/twigs form a “cover” to reduce the heat, keep more moisture in, trap blown-in seed and when decomposed, contribute to the nutrient enrichment of the soil. It is important to protect the restored area from any grazing until the newly-established plants have made seed.
Community engagement
Researchers from the NWU also communicate with farmers and land users during information days and workshops to exchange knowledge about the results from the experiments and best ways to restore the natural resource in a specific area.
Local community members and land users are involved in all the projects at different sites.
For more information, contact Prof. Klaus Kellner at 018 992510.