Impact of extreme weather events on coconut productivity in three climatic zones of Sri Lanka

Coconut is a major plantation crop in Sri Lanka, a tropical island in the Indian Ocean. The highest coconut production is found in Gampaha, Kurunegala and Puttalam districts which belong to the wet, intermediate and dry zones respectively. An increase in the frequency of extreme weather events has been observed during the recent past. This study, the first of its kind, was undertaken to assess the impact of extreme events on coconut productivity. Meteorological and coconut productivity data were obtained for the period 1995-2015 from six estates, two estates representing each of the above-mentioned districts. Extreme events were defined using maximum daily temperature (Tmax) and daily rainfall. The 90th percentiles of the daily distribution of rainfall and Tmax in the reference period were used to define high rainfall and high temperature days respectively. The days with their rainfall below the 10th percentile were defined as low rainfall days. Regression analyses between coconut productivity and the number of extreme events during the first four months after flowering were performed. In the dry zone the number of high rainfall and high Tmax days during the said period had a negative influence on productivity and the mean rainfall had a positive influence on productivity. In the intermediate zone the number of high rainfall events and the mean Tmax of the same period had a negative impact on coconut productivity. In the wet zone, while the number of extreme weather events had no influence on the coconut productivity, the mean Tmax during the first four months since flowering had a negative impact on coconut productivity.