Climate change and water and food in Africa?
Previously we understood why the distribution and frequency of rainfall in Africa is so variable. This week we are going to explore the potential impacts of climate change on this variability and distribution. It is important to understand and prepare for what might happen to water in Africa if climate change continues and worsens.
I have chosen to talk about this as Africa has been labelled the most vulnerable continent in the world to the effects of climate change (Masipa, 2017). Studies undertaken by organisations such as the World Bank and the Intergovernmental panel on Climate Change emphasised that climate change will severely impact agricultural land which will in turn affect food securities across Africa (Vogel, 2000). This is further supported by the IPCC who have argued that agricultural productivity in sub-Sharan Africa will have declined from anywhere between 9 to 21% by 2080 as a result of global warming (Masipa, 2017).
Climate change - the outlook:
Global warming is set to cause intensifications in precipitation across Africa (Allan et al, 2010). As Africa warms, there will be fewer low to medium intensity precipitation events at the expense of more “extreme precipitation events” (Allan and Oden, 2008:1484). This is significant as the problem in Africa is not the volume of rainfall, but rather the distribution and frequency of this rainfall as we learnt in my last post. The problem is that rainfall in Africa is not only temporal in distribution but also spatial. This is epitomised as Masipa (2017) states up to 2/3 of Africa’s arable land will be lost by 2025 as a result of a lack of rain and droughts. Thus, as climate change causes increased variability in the distributions and severities of rainfall events there are both potential positives and negatives for Africa depending on how this is embraced, acknowledged and adapted towards.
More specifically, river discharge will become more variable and require substantial adaptive strategies to maintain sufficient volumes of water supply for agriculture. One of these adaptive strategies may be a favourability of groundwater abstraction for farming (Figure 4) as increased extreme precipitation events are argued to lead to a greater rate of groundwater recharge than low to medium rainfall events. Such changing patterns will in turn have substantial impacts on the ability of sub-Saharan Africa to access water to irrigate its crops.
However, the extent to which such changes will impact food and water in Africa will depend on the irrigation methods adopted. For example, large-scale, intense irrigation methods (Figure 5) for certain farms underlain by geology with low bulk transmissivities may not be supported. Example's include farms around the belt of tropical Africa in countries such as Benin, Nigeria, Ivory Cost and Ghana. The extent of this limitation is epitomised as 40% of sub-Saharan Africa is underlain by aquifers that have a low bulk transmissivity (MacDonald et al, 2012). Intense large-scale irrigation will not be able to be sustained at an appropriate pace and quantity to provide the water the crops require. This is even more concerning as global warming is likely to favour greater rates of groundwater recharge which may be a problem in regions such as these.
Figure 5: An example of large-scale intense irrigation that would likely not be supported in areas with low bulk transmissivities
However, what is ironic in Africa is that in areas of low transmissivity, groundwater replenishment is regular and it is often that driest regions within Africa that have the greatest groundwater recharge rates and vice versa. Thus, although intense irrigation methods may not be supported in areas of low bulk transmissivity there is a positive to this. This positive is a kind of self-regulating effect. By this, I mean that if a farmer or resident abstracts too much water from the ground at any one time, the only people that they are likely to be affecting are themselves or those living immediately around them using the same water source. This is because the groundwater has a low bulk transmissivity and thus the affects will not be far reaching but much more isolated. This self-regulating effect can be seen as a benefit as it leads to a lack of selfishness.
Although self-regulation can be seen as a positive deterrent towards over-abstraction, there are still serious limitations for large scale farming and crop production in the parts of Sub-Saharan Africa that have low bulk transmissivities. With forecasts of an increasing propensity of groundwater recharge in Africa due to climate change, this blog has explored some very important factors that need to be considered going forward.
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