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

[22]. In Australia, Nagao et al. [58] found that water deficits from prolonged drought periods caused macadamia flower loss and tree mortality. Consequently, projections that climate change will decrease the number of rainy days and months [61,62], thus reducing moisture availability to the macadamia trees during the dry season in many parts of Malawi will drive many areas out of macadamia production. These findings confirm and, more importantly, extends the work by Dougill et al. [6], who predicted that climate change will decrease the amount and distribution of precipitation throughout Malawi, particularly the southern region, altering the suitability of important perennial crops such as tea, coffee, and macadamia in the country. Farmers are therefore encouraged to adopt moisture conservation measures (mulch- ing, rainwater harvesting, box ridging, and basins) and possibly develop irrigation infrastruc- ture to meet the water requirements for macadamia growth, particularly during the drier months of the year. Isothermality (17.3%) and the mean diurnal range (13.1%) are two other important fac- tors influencing macadamia suitability in Malawi (13.1 percent). Our findings suggest that large fluctuations in day and night temperatures, as well as increased warming (� 30 oC), are responsible for the marginal suitability for macadamia in Malawi, notably along the lakeshore and Shire valley, confirming previous research [25,27,63,64]. Such temperature increases result in increases in evapotranspiration, which raises the crop water require-

ments of macadamia, especially during critical phenological stages. Higher day tempera- tures of more than 30 oC have already been linked to excessive water loss from the macadamia plants [58]. Such moisture losses result in a disproportional supply of nutrients within the macadamia nut, limiting oil buildup and negatively affecting the nut quality [21]. As a result, predictions that climate change will increase the number of days (30.5 days per year) with temperatures above 30 oC and hot nights (40 days per year) with tem- peratures above 14 oC [65], will undoubtedly reduce the number of suitable areas for maca- damia production in Malawi. Subsequently, irrigation will be crucial for long-term macadamia production, especially during the hotter, drier months (May-November), to compensate for water lost through evapotranspiration. Fig 7. Percentage of predicted suitable areas for macadamia production using current and future climate scenarios. https://doi.org/10.1371/journal.pone.0257007.g007 PLOS ONE Macadamia integrifolia: Climate suitability of Malawi PLOS ONE | https://doi.org/10.1371/journal.pone.0257007 September 9, 2021 14 / 20