How would climate change impact water and food across Africa?

Global climate change is affecting Africa, as it is on every other continent in the world. 

Water and food security in the area already faces multiple threats stemming from climate variability, entrenched poverty, environmental degradation, rapid urbanisation and high population. Now the impacts of climate change will be superimposed onto these intertwined issues, and the relationships involved are likely to be highly nonlinear (Carter and Parker, 2009). This blog will explore some of the impacts of climate change in Africa.

Existing hydrological variability

As mentioned in the introduction, we should now know that variability is a keyword in Africa. The temporal variability of rainfall can be illustrated in Table 1 from a study by Peter and Parker. We can see that about 95% of annual rainfalls lie in the range  ±16–45% around the mean; the coefficient of variation CoV is twice higher than what you might find in the UK. This has a significant implication for the water supply that is available for food production. The unpredictability and variability in the timing of rainfall would provide extreme challenges for rain-fed agriculture, which is the dominant form of agriculture in Sub-Saharan Africa (Taylor, 2017).  

Consequently, the rainfall variability leads to the most extreme hydrological variability in river discharge in the world, the median CoV in annual river discharge is 82% in Southern Africa, whilst the global median is only at 31% (McMahon et al., 2007). 

Figure 1. Analysis of past rainfall (1948-2001) for five countries in Africa. Source: ARTES

Cascade of uncertainty 

Although climate variability continues to be a major source of uncertainty in the near term, inherent uncertainty is rooted in the limitations to the predictive capability of Global Circulation Models (GCMs) in accessing different climate scenarios, especially in data-poor regions like sub-Saharan Africa. The margin of error is already large for current GCMs, rainfall can be overestimated by up to 20% in SSA (Meehl et al., 2007). Although new GCMs are now being developed, we need to keep in mind that the continent’s climate complexity and lack of observational data mean that it is extremely challenging to accurately model and produce reliable climate projections (Bonsor et al., 2010). 

So, what will happen under climate change?

Despite the uncertainties, climate change is likely to present intensification of present variability, rather than a catastrophic change in the average state of the climate, these are some key impacts on water and food: 

• As the air gets warmer, moisture-holding capacity increases at the Clausius-Clapeyron rate (Held and Soden, 2006). A shift towards fewer lighter precipitation but more extreme events (Allan and Soden, 2008) → soil erosion, destruction of fertile, arable land 

• Much greater spatial and temporal variability in precipitation (Boko et al., 2007) → increased volatility and uncertainty on food production  

• Seasonal rainfall patterns will be exaggerated as the position of rain belts shifts, causing local changes in rainfall (Bates et al., 2007) → affects water availability for food 

• Different rainfall predictions in different regions by GCMs (Figure 2)

Figure 2. GCMs predictions of temperature changes (upper) and rainfall changes (lower) modelled with Africa within winter (Dec-Feb) and summer (Jun-Aug). Rainfall changes in northern and southern Africa are more pronounced, with up to 20% decrease in northern Africa, and up to 30% in Southern Africa. Source: Christensen et al., 2007 

Patterns of runoff will be determined by the change in precipitation, offset by increased evaporation (Arnell, 2003). Much of southern Africa (near Cape Town) which is already at low drainage is projected to experience losses in more than half of the perennial supply. This also puts pressure onto food production by a reduction in water availability for crops in drought-stricken regions (De-Wit,2006). 

What next? 

These findings highlight the potential threat to water and food, but again what we are faced with is a cascade of uncertainties. The continent is already dealing with large climatic and hydrological variability, therefore adapting to the existing variability may mean going a long way in adapting and building more resilience to deal with future changes and all the unknowns. For example, reducing dependence on rain-fed agriculture to increase adaptive capacity. 

However, it is crucial to consider all freshwater resources, not only surface water. In the next post, we will be going below the surface to explore the potentials of groundwater in a more variable climate.