Effects of Interannual Climate Variability and Climate Change on Rice Yield in Java, Indonesia

Abstract

About 60% of the nearly 40 x 106t of rice produced in Indonesia are from the island of Java. However, the rice self-sufficiencythat has been attained and maintained since 1984 could be threatened by changing climate, and has been affected by the climate variability effects of the El Nino/Southern Oscillation phenomenon. To aid policy makers and planners in formulating strategic policy options, the effects of recurring droughts and possible climate change on rice yields were studied using climate and crop models. Three models were used to simulate climate change: those of the Goddard Institute for Space Studies, Geophysical Fluid Dynamics Laboratory, and the United Kingdom Meteorological Office. Several climate scenarios were generated for Ngawi, in East Java, and Sukamandi, in West Java. These models indicate that doubling greenhouse gases would increase solar radiation by 1.2–2.1%, minimum and maximum temperatures by 7.6–16.8°C, and precipitation by 20.5–91.7%. The Goddard Institute for Space Studies transient climate change scenarios indicate that maximum and minimum temperatures would increase by 3.5 and 4.9%, respectively, in 2010, 6.9 and 9.8%, respectively, in 2030, and 11.1 and 15.7%, respectively, in 2050. The rainfall increase varies from 7.0% for West Java in 2010 to 8.7% for East Java in 2050. The Decision Support System for Agrotechnology Transfer crop model slightly under-predicts lowland rice yields of several experimental plots in three sites in Java and one site in Sumatra, but the results are almost equal to or a little higher than farm level yields. Nevertheless, the simulation outputs and experimental plots yields are closely related with a coefficient of determination value of 87%. Changes in climate in the decades of 2010, 2030, and 2050 could drastically reduce rice yield: the rice yield is estimated to decrease by about 1% annually in East Java and less in West Java. Currently, the rice yields in dry years are about one half those of normal years.