Climate change and reduced water availability have food security implications for the nation and managerial implications for all farmers, concludes Pprof James Blignaut of the Department of Economics at Pretoria University. The day of reckoning could come sooner than expected, reports Roelof Bezuidenhout.
A new study dispels any doubt SA is getting hotter and drier, moving scientists to warn government and individuals to become more resilient and develop effective adaptive responses to changing climatic conditions.
“We must take stock of the current trends and adapt our ways of thinking, acting, farming, and managing vital resources,” says the study’s lead author, Prof James Blignaut of Pretoria University’s Department of Economics. “In the process, some types of agriculture should be encouraged while others should be phased out.”
Even under pre-industrial conditions, extreme events and global factors, such as new markets or the collapse of old ones, influenced ecological and agricultural systems. Blignaut contends that in today’s interconnected world, with massively accelerating human-induced climate change, “business as usual” simply isn’t good enough.
The study
The study was motivated by the fact that agriculture is the mainstay of the country’s rural economy, and not only vital for food security but also expected to improve political stability through land reform.
The researchers worked with rainfall and temperature records for the nine provinces for the periods 1970 to 1979, 1997 to 2006, 1970 to 1989, and 1990 to 2006. Tthey concluded that the country has been about 2% hotter and at least 6% drier from 1997 to 2006 than from 1970 to 1979. All but one of the nine provinces have received progressively lower rainfall since 1970.
The exception is the Western Cape, which had consistent annual rainfall over the entire study period. Iinterestingly, instead of using minimum temperatures, the usual preferred indicators of climate change, the researchers used maximum daily temperatures because higher maximums are likely to have a bigger impact on farm output.
Prof Blignaut points out that most macroeconomic and agricultural production data are only available on an annual basis. Tthis obscures the true impact of climate change, especially at farm level, which “is really felt through changes in the timing, frequency, and intensity of rainfall events and their distribution throughout a season, and not merely in changes of annual averages.”
More water
Water use also increased dramatically over the study period. By 2000, 98,6% of surface water and 41% of the annual usable potential of groundwater was being used. And, warns Blignaut, with little scope to expand irrigation, farmers will have to increasingly rely on water-saving techniques that could drive up expenses in a sector that has a small net income margin and which already faces rapid cost increases. “Tthis will make it increasingly difficult for emerging farmers to enter the sector, despite official national policy prioritising them,” he notes. Tthe study shows both field crop production and horticulture are extremely vulnerable, particularly rainfed field crops.
“A 1% decline in rainfall is likely to lead to a 1,16% decline in maize production and a 0,5% decline in wheat production, and will likely decrease net income even in the most productive provinces,” Blignaut says. Only 1,4% of SsA’s water yield is currently available to the poor, most of whom don’t have access to piped water. “Lless and less water will be available for agriculture, with obvious implications for the rural economy,” says Pprof Blignaut. For the study, the nine provinces were clustered into four broad climatic regions based on average rainfall and temperature. Wwith the exception of a temperature decline in Mpumalanga, all other areas showed an increase – in some places by as much as 4%. For SA as a whole, the last 10 years have been on average 0,5ºC (2%) hotter than the 1970s. Changes in temperature also became less predictable, were consistently higher in absolute terms, and increased steadily over the entire review period.
The Northern Cape and the North West have been hardest hit, both in terms of percentage change and absolute change. SA as a whole received on average 40mm less rain per year over the last 10 years than during the 1970s, which is a 6% drop in average rainfall over the entire period.
Regarding rainfall variance, hot and arid areas deviated less from the average during the last 10 years than during the 1970s. The variance from the average has, however, increased for all other (less arid) areas, indicating increased unpredictability and the occurrence of extreme events. But, explains Prof Blignaut, the variance around these lower rainfall numbers is declining in the Western and Northern Cape, pointing to more predictability at low and declining levels of rainfall for the hottest, most arid regions. “The uncomfortable truth is the hotter it gets, the less rainfall there is in all regions. If this trend continues, we’ll have to look for a buffer, and ask how much surplus water we have, who’s using it, and if the trend can be changed,” says Prof Blignaut.
Cost of water
“Should demand for water grow by more than 1,4%, the only way to accommodate it would be to cut consumption in some of the current water-intensive sectors. Some tough decisions and water-allocation trade-offs are on the cards,” says Prof Blignaut. According to the study, irrigation’s use of surface water has risen steadily from 7,63 million cubic metres in 1995 to 7,92 million cubic metres in 2000 – a 4% increase. This represents 160% of the total water surplus remaining at the end of 2000.
“Surface water use is increasing rapidly, and there are no signs of a decline in any sector. If the volume of water used for irrigation increased by the same margin, without any compensatory reduction by other sectors, there must have been a deficit for the country as a whole. Furthermore, the total increase in water consumption for all sectors from 1995 to 2000 was 348 million cubic metres, implying irrigation’s portion of the increase was a whopping 84%,” Prof Blignaut says.
Use of groundwater is also increasing rapidly. By 1999 there were 1,1 million boreholes, and by 1999 groundwater use was increasing at 3,4% per year.
Estimated use at the end of 2001 equalled 49% of surface water usage. “The exploitable groundwater usage for 2000 is estimated at 9,5 million cubic metres, which implies groundwater usage was about 41% of the potential and there’s room for further development,” Prof Blignaut says. “But the surplus is dwindling fast.
“The effect of climate change on agriculture over the past 40 years, notably the 6% decline in average annual rainfall, has been mitigated by aggressively increased irrigation. But conventional irrigation methods have to change. It can’t protect production from climate change, and may well degrade and salinise soils,” Prof Blignaut warns.
How sensitive is your farming business to climate change?
One could argue the decline in net farming income in recent decades is a result of changes in climate forcing the sector to become more capital intensive, says Prof James Blignaut.
“While irrigation and capital intensification didn’t increase net income, they did soften the landing. Without them, outcome could have been much worse. For example, in the Western Cape, where viticulture plays a major role, horticulture uses irrigation extensively to offset any sudden decline in rainfall.” Should less water become available to irrigation farmers, the pressures on farming input costs are likely to increase even more.
“If the future is going to be challenging for well-established farmers, it’s going to be even more demanding for new farmers trying to enter the market. The same is true for the subsistence farmers, who own 5,6 million head of cattle (or 41%) of SA’s total of 13,8 million,” Prof Blignaut contends. The study found no direct link between rainfall and intensive poultry and beef production, since both use abstracted water. But this could be misleading regarding beef, as calves come from extensive cattle farming on veld, which is vulnerable to less rain. “Dryland field crops are also more vulnerable than horticulture or animal husbandry as they don’t have the irrigation option,” says Prof Blignaut.
Link between rainfall and output
The researchers found a strong correlation between rainfall and crop production, in both summer (maize) and winter crops (wheat). They distinguish winter rainfall (April to September) from summer rainfall (October to March). “Alarmingly, a 1% change in rainfall would lead to more than 1% change in maize production,” Prof Blignaut says. “This doesn’t bode well for the Free State, North West and Western Cape, all regions which were considerably warmer during the period 1997 to 2006 than in the three preceding decades. If it becomes even warmer and rainfall keeps decreasing, production will decrease markedly in the three major maize and wheat production areas of the country.”
Contact Prof James Blignaut on 084 720 4127
or e-mail [email protected].
