Ensemble Prediction of Brown Planthopper, Nilaparvata lugens, Overwintering Area under Future Climate Conditions

Abstract

The brown planthopper (BPH), Nilaparvata lugens (Stål), is an insect pest in rice paddies across the East Asia. Because BPH cannot survive under low temperature conditions (<12 ℃), it migrates from the tropics to temperate areas with severe winter conditions. The objective of present study was to assess potential areas for BPH overwintering in East Asia under current and future climate conditions. To predict potential overwintering areas of BPH, 176 occurrence sites, which include 88 favorable sites and 88 non favorable sites for overwintering, were obtained from literatures. Two sets of climatic variables including temperature and precipitation were used to represent temperature and humidity conditions in paddies, which are key environmental factors for overwintering of BPH. Current and future climate maps of these variables were used as inputs to species distribution models (SDMs). Five SDMs including ANN, BIOCLIM, GARP, MAXENT, and SVM were used. To reduce model uncertainty, we explored an ensemble modeling approach using multiple sets of SDMs and climate data. Climate data which were averaged over the period from 1960 to 1990 were used for current climatic conditions. Future climate data generated from five general circulation models (GCMs) with an emission scenario of A1B were used for BPH overwintering distributions in 2020s and 2050s. For future predictions, outputs of each SDM were generated using five sets of climate data from general circulation models (GCMs) and averaged into a single map. The single map was classified as presence and absence by the threshold of 0.5 for each SDM. The optimum ensemble method was applied to predict future geographical distribution of BPH overwintering area. From predictions in this study, the northern limit of BPH overwintering suitability shifted north by 100-200 Km in most regions in East Asia in the next 40 years. Therefore, future studies in monitoring migration routes of BPH are considered to be important.