BUFFER AND WETLAND MANAGEMENT GUIDELINE FOR PASTURE DAIRY FARMS

From results of a research project by the authors cited, a guideline was compiled. The guideline aims to support sustainability in the dairy sector through provision of best practice guidelines for improved management of water resources using riparian buffer zones and enhanced wetlands.

Dairy farming is mostly concentrated in areas of comparatively high rainfall in the southern and eastern provinces of the country, but still cannot be solely rain fed and thus rely heavily on irrigation. This requires high volumes of water abstraction and storage in dams often resulting in seriously reduced flows in surface waters. As a consequence, dairy farming is often a contributing factor to declining surface and groundwater quality. Furthermore, pasture layout generally aims for maximum productivity with sometimes little consideration for riparian / wetland habitat or vegetated buffers.  This not only impacts on water quality, but on habitat connectivity for biodiversity. It can also create direct costs to the farming operation through factors such as dam eutrophication where nuisance algal blooms clog equipment, increased flood risk, damage due to wetland loss and siltation of dams requiring costly maintenance.

Activities such as water abstraction, fertilization, pasture management regimes, wastewater disposal, and grazing cattle can impact aquatic ecosystems. These actions may manifest in eutrophication due to nutrient inputs, associated blooms of algae or macrophytes, human health issues related to pathogenic microbes, habitat degradation, siltation and erosion and impacts to biodiversity. Riparian and wetland buffers can address several of these issues. Buffers are defined as a strip of land with a use, function or zoning specifically designed to protect one area of land against impacts from another. In the case of dairy farms, buffers can have several benefits:

• maintenance of channel stability
• control of microclimate and water temperature
• storm water and flood attenuation
• provision of terrestrial and aquatic wildlife habitat
• sediment, nutrient, pathogen and toxin removal
• and habitat connectivity.

Buffer zones, however, offer no protection from point sources of pollution. They also offer limited protection in several scenarios including poor water quality from upstream users, watercourses under pivots, and linear agricultural drains. Recommendations to address these impacts are made through the creation and / or enhancement of wetlands.                                                                                                                                                                                                                                                                                                                                                                                                                                     The riparian buffer guideline is presented using two case study dairy farms; one in the southern Cape and the other in KwaZulu-Natal. Each step in the process to complete the Buffer Tool is explained and applied to the case study farms by way of example. Application of the site-specific Buffer Tool requires extensive desktop and field assessments. The inherent environmental attributes (e.g. soils, rainfall, slopes etc.) of each site were listed and mapped watercourses mapped during site visits.  The ecological condition and sensitivity of watercourses was determined considering existing impacts to watercourses on both farms.  Discussions were held with farm management to determine where management actions were mitigating threats versus increasing threats to watercourses.  Dairy-sector specific generalised and region-specific threats were identified and refined in the Riparian Tool. Thus, the full range of interconnected land uses that potentially occur on dairy farms were accounted for when riparian buffers were determined. 

Results of the Buffer Tool were presented under a low mitigation and high mitigation scenario, assuming minimal or maximal application of best practice guidelines respectively. Under the low mitigation scenario, the calculated buffer widths ranged between 18 - 21 m on the southern Cape farm and between 20 -30 m on the KZN farm.  In the high mitigation scenario, the buffer widths ranged between 5 – 10 m and 5 – 12 m respectively on the southern Cape and KZN farms. Buffer areas intersected with both existing non-pasture as well as pasture areas.

The cost implications of implementing buffers including the different mitigation scenarios was further explored in a Cost Benefit Analysis. The assessment considered three cost categories: establishment costs; maintenance costs and opportunity costs. This determined that the main cost associated with establishing buffer zones is the income forgone from reduced pasture area which is seen as a recurring annual cost (opportunity cost).  The total respective area of pasture conversion under high and low mitigation for the southern Cape farm was 39.3 ha and 16.91 ha, compared to the KZN farm with 26.12 and 11.28 ha.  In both cases this was approximately 5% of pasture area reduced to around 2% under high mitigation scenario.

Along with the guidelines for implementing riparian and wetland buffers, the guideline also provides a range of practical solutions aimed at improving aquatic ecosystem health on dairy farms. It is unlikely that dairy management teams will be able to implement all measures at once, as substantial efforts will be required. Rather, it is recommended that farm managers enlist the assistance of an aquatic scientist to compile a watercourse management / rehabilitation plan which may or may not include neighbours to enable cost-sharing. Implementation of the plan can then focus on various goals over the short- to long-term. It is hoped that milk buyers and dairy-specific sustainability trackers consider the inclusion of some of these interventions to encourage a more widespread uptake across the sector.