Southern Africa is the second region in the world to be confronted by a debilitating water deficit (the first was the Middle East and North Africa) (Turton, 2000). Within the region, South Africa stands out as one of the most water-scarce countries. The country is also characterised by extremely variable rainfall, both geographically and over time. In the 12% of the country that is suitable for the production of rain-fed crops, productivity tracks rainfall, making farming a challenging business. Climate change predictions are that rainfall will be more infrequent but more intense. This will shrink the country’s arable land and increase agricultural unpredictability. Farmers will find it increasingly difficult to increase productivity to meet the growing demand for food. This highlights the need for sound cropping and rangeland production practices to retain soil integrity despite these predicted intense rainfall events.
Irrigation is an age-old method of increasing agricultural productivity. It expands the arable area, improves yield and increases cropping frequency (sometimes enabling two or even three crops a year). In South Africa only 1,5% of the land is under irrigation, producing 30% of the country’s crops (South African Yearbook, 2008/9). At first glance, expanding irrigation seems the obvious means of increasing productivity, but all of South Africa’s irrigable land (estimated at 1,2% of the country) is already cultivated, with irrigation now rapidly expanding into unsuitable areas and negatively impacting the environment. Of particular concern is that irrigation is already by far the biggest water use in South Africa. Year 2000 data showed irrigation extracting 63% of the country’s available surface water (Water Accounts for South Africa, 2000). With 98% of the available water resources allocated, there is little room for increased extraction, particularly as other sectors compete for the surplus (which is itself dependent on rainfall). South Africa has few exploitable aquifers and extracts groundwater for only 13% of its supply. There is
some room for increased groundwater extraction in the south-east of the country, but in other areas groundwater is already overexploited, with water tables falling at an alarming rate (South African Yearbook, 2008/9).
Land management on farms has a major impact on water availability and quality. Soil from eroded areas, for example, flows into rivers, changing their flow and reducing the storage capacity of dams. This results in the need for expensive water treatment/filtration systems before water can be used by industrial and domestic users. Poorly applied fertilisers run off into rivers, polluting water sources and causing algal blooms. These blooms deplete the water’s dissolved oxygen and produce toxins, killing aquatic life. Pesticides from poorly managed farms are also a major source of water pollution, with devastating effects on the health and wellbeing of people and the environment. Often less than 0,1% of crop-sprayed pesticide reaches the target pest – the rest enters the environment (Pimental & Levitan, 1986). A 2004 water quality study of the Lourens River in the Western Cape detected high pesticide levels downstream of the farming area (Dabrowski et al., 2002). Levels of contamination were extremely high, exceeding both the national water quality standards and those established by the US Environmental Protection Agency (EPA). One of the pesticide chemicals found in the water was endosulfan, a highly toxic bio-accumulating neurotoxin and endocrine disruptor that is banned in more than 50 countries (National Resources Defence Council, 2008).
Agriculture: Facts and trends South Africa
Dr Morné du Plessis, CEO WWF-SA