Impacts of climate change on agro-climatic suitability of major food crops in Ghana

3.4 Suitability and suitability changes of individual crops Under current climatic conditions, the suitability of maize is very variable across the country with no specific regional distribution. Optimal suitable areas for maize cover 22% (51323 km2) of the country (Figs 3A and 4A). Under projected climatic conditions the areas that have opti- mal suitability for maize production will decrease by 12% (6084 km2) and by 14% (7171 km2) under RCP2.6 and RCP8.5 respectively as suitability transition from being optimal to moder- ately suitable and marginal. These are the largest changes from the optimal suitable areas of the crops modelled in this study. Areas that have marginal suitability are projected to increase by 8% (6885 km2) under RCP2.6 and by 7% (5703 km2) under RCP8.5 scenario, with limited areas decreasing by 11% or 5800 km2 (RCP2.6) and by 8% or 4508 km2 (RCP8.5) (Figs 3B and 3C and 4A and Table 4). Sorghum was modelled as having largest area for which it is optimally suitable (28% or 66731 km2), which is the highest of the four crops for this category (Figs 3D and 4B). Under climate change, the optimal suitability areas for sorghum are projected to decrease by 10% (6445 km2) and 13% (8716 km2) decrease under RCP2.6 and RCP8.5 respectively (Figs 3E and 3F and 4B). Some parts of northern Ghana that have limited suitability for sorghum will become suitable under both RCP2.6 and RCP8.5 with an evident northwards shift in sorghum suitability under climate change. The areas that are unsuitable for sorghum are projected to

increase by 12% or 7263 km2 (RCP2.6) and 13% or 7601 km2 (RCP8.5) by the 2050s (Fig 3E and 3F and Table 4). Cassava was modelled as mostly suitable in the southern forested bimodal rainfall areas of Ghana (Fig 3G). Under RCP2.6, the results show that by the 2050s, optimal suitable areas for cassava will decrease by 7% (2798 km2) while under RCP8.5, they will decrease by 9% (3731 km2) (Fig 4C). Concurrently, the areas that have limited suitability for cassava will also slightly decrease by 4% (3039 km2) under RCP2.6 and by 3% (2338 km2) under RCP8.5 from the cur- rent 35%. The results showed that 48% (115868 km2) of Ghana can produce groundnuts (opti- mal and moderate suitability) under current climatic conditions (Fig 3J). Optimal suitable areas (17% or 39861 km2) are mostly located in the northern and central zones of Ghana (Fig 3K and 3L). Under projected climate change, the results show that the areas that have optimal suitability for groundnuts will decrease by 3% (1498 km2) under RCP8.5 but will remain stable at 17% (+169 km2) under RCP8.5, a trajectory different from other crops modelled in this study (Table 4 and Fig 4D). 3.5 Climatic suitability of multiple crops for current and future climatic conditions The suitability of each pixel for multiple crops was evaluated by determining the number of crops in each suitability class suitable for that pixel. Under all climatic conditions, none of the areas has optimal suitability for all the four crops in Ghana (Fig 5A). Under current climatic

conditions, 2% (3716 km2) of the country has moderate suitability for at least three of the four crops. This area is projected to remain unchanged under both RCP2.6 and RCP8.5 (Table 5 and Fig 4B and 4C and S2 Table). Similar significant decreases in suitability are also projected for areas that have moderate suitability for at least two of the four crops as these will decrease to 5% (12837 km2) under RCP2.6 and 6% (13512 km2) under RCP8.5. Much of these high suitable areas will become suitable for fewer crops under climate change as areas that are moderately suitable for all the four crops will increase to 1% under both RCP2.6 (3040 km2) and RCP8.5 (3378 km2) while those moderately suitable for two crops will increase from 19% (44591 km2) to 24% or 57427 km2 (RCP2.6) and 25% or 60130 km2 (RCP8.5). Under both scenarios, the areas that are PLOS ONE Climate change and food crops suitability in Ghana PLOS ONE | https://doi.org/10.1371/journal.pone.0229881 June 29, 2020 9 / 21