Climate change and climate variability are projected to alter the geographic suitability of lands for crop cultivation. Early awareness of the future climate of the current cultivation areas for a perennial tree crop like coconut is needed for its adaptation and sustainable cultivation in vulnerable areas. We analyzed coconut’s vulnerability to climate change in India, based on climate projections for the 2050s and the 2070s under two Representative Concentration Pathways (RCPs): 4.5 and 8.5. Based on the current cultivation regions and climate change predictions from seven ensembles of Global Circulation Models, we predict changes in relative climatic suitability for coconut cultivation using the MaxEnt model. Bioclimatic variables Bio 4 (temperature seasonality, 34.4%) and Bio 7 (temperature annual range, 28.7%) together contribute 63.1%, which along with Bio 15 (precipitation seasonality, 8.6%) determined 71.7% of the climate suitability for coconuts in India. The model projected that some current coconut cultivation producing areas will become unsuitable (plains of South interior Karnataka and Tamil Nadu) requiring crop change, while other areas will require adaptations in genotypic or agronomic management (east coast and the south interior plains), and yet in others, the climatic suitability for growing coconut will increase (west coast). The findings suggest the need for adaptation strategies so as to ensure sustainable cultivation of coconut at least in presently cultivated areas.

The reproductive phase of coconut is extremely sensitive to high temperature, manifesting as button (female flower) shedding and poor nut set. The progamic phase, which elapses from pollination to fertilization, is one of the most critical phases during the sexual reproduction processes in annuals and fruit trees and is extremely vulnerable to high temperature. Hence, we investigated the progamic phase of the tall coconut cultivar West Coast Tall (WCT) and the effect of high temperature on the phase under both in vivo and in vitro conditions. Coconut has a long pistil and its length was found to be 18.2 ± 4.9 mm in WCT. Pollen germination on stigma occurred one day after pollination and the pollen tube traversed through the pistil and reached micropyle of ovule four days after pollination at 29 °C. However, high temperature (T_max > 33 °C), both under in vivo and in vitro conditions, significantly reduced pollen tube growth through the pistil, suggesting its inability to reach the ovule on time to effect fertilization. High temperature also advanced nectar secretion and stigma receptivity and the receptive stigma was dry without nectar, rendering it unappealing to insect pollinators. Thus, both poor pollination and the inability of pollen tube to reach the ovule on time to effect fertilization could be the cause of poor nut set in the coconut variety WCT under high temperature. However, it was encouraging to note that the pollen tube growth was less vulnerable to elevated temperature under high humidity, suggesting that climate change effect on coconut in coastal regions with high humidity might be less severe.