The agricultural sector is critically important to Africa, both in terms of social and economic development. Over 60 per cent of Africans depend directly on agriculture for their livelihoods (FAO, 2003). Production ranges from small-scale subsistence farming to large-scale export industries. Agriculture contributes to about 50 per cent of Africa’s total export value and approximately 21 per cent of its total gross domestic product (GDP; Mendlesohn et al., 2000). 

Agricultural activity is highly sensitive to climate change, largely because it depends on biodiversity and ecosystems. Sufficient freshwater supplies, fertile soil, the right balance of predators and pollinators, air temperature and average weather conditions all contribute to continuing agricultural productivity. 

Human interventions, such as excessive extraction of natural resources, forest clearance for pasture or cropland, large-scale monocropping and use of chemical fertilisers and pesticides, have resulted in biodiversity losses. These can ultimately damage an ecosystem’s capacity to adapt naturally to changes in the climate. The resulting ‘simplification of agroecosystems brings losses in fertility and an increased risk of exposure to new pest and disease variants’ (Ensor, 2009). 

Drought is one of the most serious hazards for Africa’s agricultural sector in certain areas. By 2100, regions of arid and semi-arid land are expected to expand by 5-8 per cent, or 60-90 million hectares, resulting in agricultural losses of between 0.4-7 per cent of GDP in northern, western central and southern Africa (IPCC, 2007). A reduction in land suitable for rain-fed agriculture and crop production is also expected by the 2080s. In southern Africa, this could lead net crop revenues to drop by as much as 90 per cent. However, climate adaptation could reduce these effects (IPCC WGII, 2007). The importance of rain-fed agriculture varies regionally, and is most significant in Sub-Saharan Africa. Here, it accounts for about 96 per cent of total cropland (World Bank, 2008). 

The impact on maize is of particular concern in western and southern Africa, while decreases in North Africa’s wheat yields could increase famine (Warren et al., 2006). In contrast, increased temperatures and rainfall changes in certain areas – for example, parts of the Ethiopian highlands and Mozambique – could lead to longer growing seasons and increased agricultural production (IPCC, 2007). 

The net balance in cereal production potential is expected to be negative, with up to 40 per cent of sub-Saharan countries set to lose substantial shares of their agricultural resources (Fischer et al., 2002). Sea level rises resulting in saltwater intrusion into inland freshwater supplies could lead to crop failure in coastal countries. These crops potentially include rice in Guinea; palm oil and coconuts in Benin and the Ivory Coast; mangoes cashew nuts and coconuts in Kenya; and shallots in Ghana (IPCC, 2007). 

Africa’s poorest people live in rural areas and depend mostly on agriculture for food and income. These people are the most vulnerable to hunger, as well as dependence on food imports and food aid caused by deteriorating farming conditions. Currently, around 40 per cent of sub-Saharan Africa’s population is undernourished. By the 2080s, this number could increase by as much as 50 million to approximately 240 million. 

As for livestock, a warming of up to 5°C from 2006 average global temperatures could benefit some small-scale farmers in some areas who keep goats and sheep as they are more heat tolerant than other species. By contrast, the same temperature rise could reduce the income of large-scale livestock farmers dependent on nonheat tolerant cattle by as much as 35 per cent, or US$20 billion a year compared to 2006. Increased rainfall would reduce livestock revenue for both large and small farms, due primarily to a reduction in the numbers of animals (Seo & Mendelsohn, 2006b). 

Given that large farms dominate Africa’s agricultural sector, the overall effect on net livestock revenue equates to losses of billions of US dollars. Table 1 shows these findings converted to a pre-industrial temperature baseline, based on the general consensus that global mean temperature has risen by approximately 0.8°C since the pre-industrial era (Hansen, 2006). As ecosystems shift from savannah to forest (and other areas where new disease vectors may emerge) small-scale livestock farmers will suffer losses. This will result from farmers lacking the information, skills and technology necessary to change animal stock to more suitable and adaptable species, or to shift from livestock to crop production (Seo and Mendelsohn, 2006b). 

In coastal regions, coral bleaching, changes in water flows and salinisation of freshwater sources are expected to deplete fish species (IPCC WGII, 2007). Upwelling, an oceanic phenomenon whereby nutrient-rich colder water is driven towards the surface by the wind, will also be a contributing factor. Temperature rises in African lakes, combined with reductions in mean annual rainfall, are also expected to impact negatively on fish supplies. Wetlands and shallow rivers may become completely dried out (FAO, 2008). 

Despite the projection that food production and livestock rearing may benefit from climate changes in some regions, cereal production in Africa is expected to halve by 2050 (Parry, 2007). By this point, global food production will need to have been increased by 70 per cent to meet increasing demand from a constantly expanding global population (FAO, 2009). 

More than 60 per cent of the world’s population growth between 2008 and 2100 will be in sub-Saharan Africa. Climate change therefore poses a serious challenge to the future food security of millions of Africans (World Water Assessment Programme, 2009). This in itself poses a severe threat to the region’s ability to cope with and respond to other expected impacts of climate change. 

Courtesy: Christian Aid