Environmental sustainability at the farm level hinges on the way in which the farm falls within, and interacts with, its surrounding environment. In ecological economics, the farm and its operations are seen as a subset of the environment. The resilience of the farming system is therefore very much dependent on its supporting ecosystems, where these ecosystems provide a number of invaluable services.
The level of ecosystem service provision obviously varies with the type, extent and health of the natural environment. But, in the context of South Africa’s generally water-stressed environment, wetlands, together with riparian zones, are by far the most valuable terrestrial systems. Wetlands are well known for their ‘sponge’ functionality – their ability to absorb and dissipate floodwaters, regulating stream flow through both wet and dry periods. Despite this, wetlands are vulnerable and threatened ecosystems across the country – more than 50% of wetlands in South Africa have already been lost due to various land uses.
The following ecosystem services typically provided by wetlands give good reason for their conservation within a South African farming environment:
- Flood attenuation: many water-stressed regions in South Africa are subject to high intensity rainfall over very short periods, often resulting in flash floods. Wetlands are effective in spreading out and slowing down floodwaters, thereby reducing the severity of floods downstream.
- Regulation of stream flow: wetlands are often compared to sponges, in their ability to absorb water in wet periods, and release it during dry periods.
- Sediment trapping: wetlands reduce runoff velocity, and through their vegetation are effective in trapping and retaining sediment.
- Phosphate and nitrate assimilation: removal by the wetland of phosphates and nitrates carried by runoff water. This takes place through the presence of wetland vegetation and the action of anaerobic bacteria (which would otherwise not exist in fast-flowing, energised streams or rivers).
- Erosion control: wetlands can limit the extent of erosion, predominantly through the protection provided by vegetation, and through their ability to reduce stream flow velocity.
- Maintenance of biodiversity: through the provision of habitat and the maintenance of natural processes, wetlands contribute to supporting and maintaining biodiversity.
The combination of these ecosystem services is nearly impossible to substitute, if not extremely costly. Their value tends only to be realised once their functionality has been lost, a process that is essentially irreversible. For farmers that take the sustainability of their farming practices seriously, it is vital that they consider the role wetlands play within their farming environment, and conserve these important systems where possible.
The way in which wetlands are perceived within the farming environment is definitely changing, represented by the protection of wetlands under national legislation, and the increasing momentum of Working for Wetlands in the rehabilitation of wetlands nationally.
Under the Conservation of Agricultural Resources Act (CARA) 43 of 1983, regulation 7 of GNR. 1048 states that no land user shall utilise the vegetation in a vlei, marsh, or water sponge in a manner that may result in the deterioration of this natural resource. Except on authority of written permission, no land user shall drain or cultivate any vlei, marsh or water sponge on his farm unit (unless this took place prior to the commencement of GNR. 1048 on the 25th of May, 1984).