Variability in Africa's Physical Environment and Climate Change Impacts

Diverse Africa 

Aside from Africa’s pretty green scenery and a wide array of exotic animals, Africa is highly diverse and variable across space and time in a number of physical attributes such as biomes, precipitation patterns, topography and groundwater resources. The Hadley Cell of the atmospheric circulation over Africa results in a desert type biome in the north and south, and a tropical biome in the centre of Africa (Figure 1) due to high pressures at higher latitudes of 30°N and 30°S, and low pressure near the equator which facilitates high levels of rainfall in the tropics (Figure 2). African climate is largely determined by the interaction of three large-scale climate systems, the ITCZ, El Nino-Southern Oscillation and annual variability of Monsoon systems (Conway, 2009). The ITCZ has an extremely important role in distributing rainfall temporally and spatially over Africa. Elevation levels vary across the continent where there is low elevation in the north-east and high elevation in the south-west (Figure 3). Groundwater resources are underlain by different geological rock types and thus affecting different productivity levels (Figure 4). It is the complexity of Africa’s physical environment that should be carefully considered when discussing the impacts of climate change. 

                   Figure  1. Biomes of Africa (UNEP)    Figure 2. Precipitation patterns of Africa (UNEP)

                        Figure 3. Elevation of Africa      Figure 4. Geology of Africa (MacDonald, et al., 2012)

What is climate change?

The IPCC explains that climate change is a result of anthropogenic influences on natural climate systems and thus forcing them to change (IPCC, 2014). A major cause for climate change is due to increases in anthropogenic carbon dioxide emissions during the industrial era of the mid-20^th century and since then the subsequent economic and population growth (IPCC, 2014). Brian Kahn (2016) reports that September 2016 is a milestone in the world’s climate whereby carbon dioxide levels have surpassed the ‘symbolic’ mark of 400 ppm. The IPCC’s Fifth Assessment Report explains that we can expect more variable rainfall patterns and temperatures across Africa (Niang et al., 2014), and thus surpassing the 400ppm mark can only make these patterns more variable than ever. In a world where governments and international organisations have finally come together to tackle climate change, it just clearly shows that our current methods appear ineffective and more work is required when facing this challenge. 

Brief Overview of the Impacts of Climate Change on Africa

• Increased frequency in extreme rainfall (New et al., 2006) – IPCC (2014) for example, explains that southern Africa is experiencing increases in extreme rainfall and New et al. (2006) has shown statistically significant relationships between extreme precipitation and total precipitation whereby increases in extreme precipitation and decreases in total precipitation show that average intense rainfall is concentrated on extreme rainfall days in southern and western Africa.
• Increased frequency and intensity of droughts and floods in some regions – It is more likely that the southern and northern most parts of Africa will become hotter and drier where temperatures are projected to increase by 4°C and rainfall levels are expected to fall by 10-20% (IPCC, 2007). The IPCC AR5 suggests that temperature across Africa is likely to rise more quickly than other land areas and this is most pronounced in arid areas.
• A decrease in perennial stream or river drainage density (de Wit & Stankiewicz, 2006) – Regions receiving more than an average of 1000mm of rainfall per year and experiencing a 10% in precipitation will see a decrease in drainage by at least 17% (Figure 5). Areas with 500mm of rainfall would see a drop of 50% in surface drainage with a 10% decrease in precipitation (de Wit & Stankiewicz, 2006). Central and eastern Africa is expected to see increases in precipitation whereas precipitation in northern and southern most areas Africa is expected to decrease. 

Figure 5. Drainage density and rainfall (de Witz & Stankiewicz, 2006)

• A reduction in agricultural crop yields – General consensus of climate change impacts on agriculture shows that rain-fed crop yields are expected to fall by up to 50% by 2020 in many African countries where small scale farmers are expected to be most affected (IPCC, 2014). Roudier et al. (2011) predicts that Sudano-Sahelian countries in north-western Africa is likely to be more affected (median yield loss of –18%) than Guinean countries in south-western Africa (–13%). However, Roudier et al. (2011) also found that higher carbon fertilisation processes have the potential to improve yields for C3 (e.g. soybean) and C4 (e.g. staple crops like maize) crops. In East Africa, Thorton et al. (2009) predicted that maize yields and bean yields are likely to increase in the east African highlands such as the Kenyan and Ethiopian highlands. 

The impacts of climate change are world-wide but the same cannot be said for Africa; it is unlikely that there will be a wide African-scale effect of climate change. Instead it is more likely that climate change effects will vary within different locations of Africa due to its large landmass and heterogeneous physical and environmental features (Collier et al., 2008).

Concluding thoughts:

Africa consists of highly diverse and variable physical attributes, such as rainfall patterns, temperature, land surface geology, and elevation. Thus we should not assume that the impacts of climate change in Africa is simply homogenous on a wide continental scale, instead the impacts of climate change are regionally localised to the environmental conditions of that area. Impacts on the hydrological cycle include extreme rainfall patterns, overall decreased rainfall levels, flooding, and droughts are likely to occur unevenly across Africa.

Although the use of the term impact should be carefully considered – the impact of climate change on the hydrological climate is negative, however climate change impacts also appear positive in other areas such as carbon fertilisation processes.
Thus this blog will continue to explore the impacts of climate change on water resources and systems in Africa, and thus the impacts on people’s well-being and livelihood in Africa.