Ghana: Agriculture

Agriculture is amongst the sectors most exposed to climate change. Smallholder farmers in Ghana are increasingly challenged by the uncertainty and variability of weather that climate change causes, particularly in the northern regions of Ghana. Since crops are predominantly rainfed (as less than 1 % of the national crop area is irrigated), crop yields depend on water availability and are susceptible to drought. The impacts of climate change on the agricultural sector will be crop-specific and also site-specific with major negative impacts expected for maize in the central to northern parts of the country [24]. Yet, the high uncertainty of water availability projections (Figure 10) translates to high uncertainty in drought projections (Figure 11). According to the median over all models employed for this analysis, the national crop land area exposed to at least one drought per year will hardly change in response to global warming. However, there are models that project an increase in drought exposure. Under RCP6.0, the likely range of drought exposure of the national crop land area per year widens from 0.3–8.8 % in 2000 to 0.5–21.0 % in 2080. The very likely range widens from 0.1–25.0 % in 2000 to 0.1–53.0 % in 2080. This means that some models project more than a doubling of drought exposure over this time period, while others project no change.

Figure 11: Projections of at least once per year exposure of crop land area to drought for Ghana for different GHG emissions scenarios.

In terms of yield projections, model results indicate a clear negative yield trend for maize and millet under both RCP2.6 and RCP6.0. As a best estimate, compared to year 2000, yields averaged over the whole country are projected to decline by 9% for maize and 10% for millet by 2080 under RCP6.0, and by 4% and 5% under RCP2.6, respectively. Yields of cassava, groundnuts and field peas, on the other hand, are projected to significantly gain from climate change. Under RCP6.0, yield increases by 2080 relative to year 2000 are projected to amount to 33% for cassava, 14% for field peas, and 3% for groundnuts. A possible explanation for the positive results under RCP6.0 is that cassava, groundnuts and field peas are so-called C3 plants, which follow a different metabolic pathway than maize and millet (which are C4), and thus benefit more from the CO2 fertilization effect under higher concentration pathways. Cassava and groundnuts are also more tolerant to both low and high rainfall extremes.

Figure 12: Projections of crop yield changes for major staple crops in Ghana for different GHG emissions scenarios assuming constant land use and agricultural management, relative to the year 2000.

[24] L. Murken et al., “Climate Risk Analysis for Identifying and Weighing Adaptation Strategies in Ghana,” 2019.