Impact of projected climate change on cropping pattern of agro ecological units of northern Kerala

Abstract

Climate change poses a developing threat to sustainability of social and economic development, livelihoods, and environmental management across the globe. Characterizing the ecosystems using the AEZ concept is a good decision-making approach for variety of farming activities performed by the farmers and is a useful tool for studying the impact of climate change. The objectives of this study are (1) to study rainfall variability and to determine water availability periods of Agro ecological units of southern Kerala under different climate change scenarios. (2) To study the impact of projected climate change on cropping pattern, crop calendar and the possible changes in the water requirements of major cropping systems prevailed in the various Agro ecological Units of northern Kerala. Daily rainfall data for the period 1991-2014 were collected from the India Meteorological Department, Thiruvananthapurm. Weather cock v.1.5 was used for converting the daily weather data into standard week, month and seasonal formats. It is also used to compute PET and Thornthwaite water balances. CROPWAT model was used for the calculations of crop evapotranspiration, crop water requirements and irrigation requirements for the development of irrigation schedules under various management conditions and scheme water supply. The annual rainfall availability in most of the AEUs of Kozhikode, Kannur, Kasaragod and Wayanad districts show an increasing trend in the projected climate. The number of annual rainy days generally shows a linear trend. The seasonal rainfall of southwest and summer monsoon will show an increase from the current situation where as northeast monsoon and winter will have a decreasing trend. In projected climate of both RCP 4.5 and 8.5 the number of months having the surplus and deficit have a similar trend compared to present situation. The crop evapotranspiration values of rice-based cropping system will show a tendency to decrease. In perennial cropping systems of coconut based and rubber the projected crop evapotranspiration will have a reduction from the presentsituation whereas in coffee-based cropping system the ETc will have an increasing trend. The irrigation requirement of all the major cropping systems will increase from the present situation except in the case of rice-fallow-fallow. The length of growing period of the cropping season in the major rice growing areas of different AEUs are getting shorter with slight differences among various agro-ecological units, implying a higher risk of operating under projected climate as per RCP 4.5. The sowing date will be delayed up to three to five weeks. It can be also observed that the crops will have to suffer water stress during the grain filling stage and will be under heavy rains at time of harvest in almost all the considered cases.