Climate suitability predictions for the cultivation of macadamia (Macadamia integrifolia) in Malawi using climate change scenarios

projections, the existing distribution of climatically suitable areas for macadamia closely matches the crop’s occurrence areas. 3.4.The impacts of climate change on macadamia in Malawi The impacts of climate change on macadamia suitability in Malawi are depicted in Table 4, Fig 6. By the 2050s, the extent of suitable areas for macadamia is projected to decrease under both emission scenarios utilized in this study. Our projections show a net loss of 18% and 21.6% (Table 4) of suitable areas for macadamia production under RCP 4.5 and RCP 8.5, respectively. This translates to 17,015 km2 (RCP 4.5) and 20,414 km2 (RCP 8.5) of Malawi’s total cultivat- able surface area. Lower altitude areas (0–900 m.a.s.l.) will experience the greatest decline in suitability. These losses will be more pronounced in Malawi’s southern region, estimated to lose between 81.7% (RCP 4.5) and 85.2% (RCP 8.5) of all its current suitable areas due to pro- jected drier and hotter conditions in the next coming decades. Due to climate change, the Thyolo district, which is currently Malawi’s most productive and largest macadamia growing area, is expected to lose 100% (1228 km2) of its suitable areas for macadamia production. In addition, the ensemble model predicts that the area suitable for macadamia in the country’s central region will shrink by at least 7.2% (6,784.1 km2) (RCP 4.5) and 8.4% (7,950.1 km2) (RCP 8.5). For the northern region of Malawi, the suitability for macadamia is predicted to decline by 2% (1,850 km2) and 4% (3,730 km2) under RCP 4.5 and RCP 8.5, respectively.

Despite the projected losses in suitable areas for macadamia production due to climate change, our predictions suggest that 39.1% (36,910 km2) and 35.5% (33,511 km2) of Malawi’s surface area will remain suitable for the crop under RCP 4.5 and RCP 8.5, respectively (S6 Table). The results from the intermediate scenario show that 18.6% (17,543 km2), 18.5% (17,491 km2), and 2% (1,876 km2) of Malawi’s cultivatable areas will remain suitable for macadamia production in the 2050s in the central, northern, and southern regions, respectively (Fig 7, S7 Table). The outcomes for the pessimistic scenario suggest that approximately 17.3% (16,377 km2), 16.5% (15,611 km2), and 1.6% (1,523 km2) of Malawi’s land will remain suitable for macadamia in the central, north- ern, and southern regions, respectively. In addition, based on RCP 4.5 and RCP 8.5, our model predicts an average gain in suitable areas of +0.22% (207 km2) and +0.5% (476 km2). These newer areas are expected to occur in Dedza (Mua and Chipansi), Mangochi (Namwera and Chaponda), Salima (Kasamwala), and Thyolo (Thekerani) districts. However, these only apply to a small por- tion of the country and cannot compensate for the country’s decreased suitability. 4. Discussion 4.1.Contribution of variables to the suitability of macadamia Precipitation and temperature have been identified as critical factors influencing crop growth and yields worldwide [53]. We find that in Malawi, suitability for macadamia is influenced by

Fig 5. Current suitability for macadamia production in Malawi. The model results were exported into Arc GIS Pro Software version 2.5 to generate the map in this figure. https://doi.org/10.1371/journal.pone.0257007.g005 Table 4. Simulated impacts of climate change on macadamia suitability in Malawi. Region RCP 4.5 RCP 8.5 Area (km2) Percentage (%) Area (km2) Percentage (%) Central 6,784.1 7.2 7,950.1 8.4 Northern 1,850 2.0 3,730 3.9 Southern 8,380.9 8.9 8,733.9 9.2 Total 17,015 18 20,414 21.6 https://doi.org/10.1371/journal.pone.0257007.t004 PLOS ONE Macadamia integrifolia: Climate suitability of Malawi PLOS ONE | https://doi.org/10.1371/journal.pone.0257007 September 9, 2021 12 / 20