| Brown planthopper Nilaparvata lugens St l，one of the major pests of rice-growingregions in Asia, is a typical r-strategist, whose population dynamics is dependent onclimate. There exists a clear upward trend in global temperatures in recent years, especiallyin north hemisphere where China is located. Warming is bound to affect the biologicalcharacteristics and behavior of the brown planthopper, such as distribution, overwinteringregion, developmental rate, voltinism and migration, thereby affecting its populationdynamics. In-depth understanding of future climate warming impact on the brownplanthopper may help establish a future comprehensive management strategy for the pest,and ensure food security in the future. In order to reduce uncertainty of global warmingpredictions and improve the credibility of the evaluation results, future meteological datagenerated by15GCMs (Global Circulation Models, GCM) coupled with three climatescenarios (A2, A1B, and B1, representing high, medium, low greenhouse gas emissionscenarios) were used in GIS (geographic information system) analysis of the distributionsof the brown planthopper’s northern overwintering boundary (northern boundary ofintermittent overwintering region and northern boundary of safe overwintering region) andthe area changes in overwintering regions for four periods (baseline1961-1990,2020s,2050s and2080s). And, voltinism of the brown planthopper in northern, central andsouthern rice-growing regions in three periods (1961-1990,1991-2020,2021-2050) waspredicted using the meteorological data downscaled by PRECIS (Providing RegionalClimates for Impacts Studies)by an accumulated temperature method. The main findingsare as follows:1. Overwintering boundary and area of intermittent overwintering region. Comparedwith the baseline period, northern overwintering boundaries of the brown planthopper in2020s,2050s and2080s will shift northward progressively with time. Distribution patternand the northward shift scope vary among the climate scenarios in each period. Northernoverwintering boundary shifts at a smaller scope in the southwest region than in thesouthern and southeastern regions. Compared with the baseline period, the area ofintermittent overwintering region under A2, A1B and B1scenarios will increase by 14.15%,20.39%and11.47%, respectively, in2020s; by41.09%,42.57%and29.66%,respectively, in2050s; and by92.11%,76.14%and46.27%, respectively, in2080s.Contributions of model, period and climate scenario to the variation of the area increase ofthe intermittent overwintering region are: period> period*model> model> period*climate scenario*model> climate scenario> period*climate scenario> climate scenarios*model, each accounting for39.01%,17.5%,13.5%,10.21%,6.82%,6.66%and6.32%ofthe variation of the area increase of the intermittent overwintering region, respectively.2. Safe overwintering boundary and area of safe overwintering region. Similar tonorthern intermittent overwintering boundary, compared with the baseline period, northernsafe overwintering boundaries of the brown planthopper in2020s,2050s and2080s willalso shift northward progressively with time. The northward shifts under A2and A1Bscenarios are more obvious than that in B1scenario. Compared with the baseline period,the area of safe overwintering regions under A2, A1B and B1scenarios will increase by0.61,0.84and0.46folds, respectively, in2020s; and by2.24,2.36and1.17folds,respectively, in2050s; and by6.33,5.35and2.35folds, respectively, in2080s.Contributions of model, period and climate scenario to the variation of the area increase ofthe safe overwintering region are: period> model> periods*model> climatic scenario>period*climate scenario> period*climate scenario*model> climatic scenario*model,each accounting for53.69%,14.57%,9.72%,8.74%,7.61%,2.91%and2.76%of thevariation of the area increase of the safe overwintering region, respectively.3. Voltinism. Under climatic scenario A2, except in the period1961-1991for theCentral China rice-growing region (Wuhan, Nanjing and Hangzhou), the number ofgenerations of the brown planthopper in all9stations in the three rice-growing regions willincrease in each period, but the increase rate differs among the stations and the timeperiods. From1961to2050, there will be an increase of0.2generations/10a in the SouthChina rice-growing region,0.1generations/10a in the Central China rice-growing regionand0.08generations/10a in the North China rice-growing region. Within each period,number of generations varies between different years. Compared with the period1961-1990, number of generations of the brown planthopper in period2021-2050willincrease less than0.5generations in the North China rice-growing region,0.5-1.0generations in the Central China rice-growing region, and1.0-1.4generations in the SouthChina rice-growing region.4. Conclusions. In summary, the overwintering boundaries of the brown planthopperwill shift northward with climate warming in the future and the overwintering region willalso increases. This trend is gradually strengthened over time, and is more obvious underscenario A2and A1B than under the scenario B1. Even though the scenario A2ischaracterized by a relative high greenhouse gas emission, increase rates/folds of the area ofintermittent and safe overwintering regions under it are less than those under scenario A1B until the2080s. Influence of climate warming on the overwintering boundaries in thesouthwest region is less than that in other regions. Voltinism of the brown planthopper willincrease under global warming in the future, but more in the southern rice-growing regionthan in the northern rice-growing region. There are great fluctuations in climate warmingbetween years, which results in much variation between-year in the number of generationsof the brown planthopper. The number of generations of the brown planthopper in2050islikely to increase by less than1generation in the North and Central China rice-growingregions, and about1generation in the South China rice-growing region. |
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