Prediction of Fall Webworm's Potential Suitable Geographic Distribution in Different Weather Conditions in China
|School||Chinese Academy of Forestry|
|Keywords||Fall Webworm climate warming suitable geographic distribution generations risk level|
Hyphantria cunea, the Fall Webworm, which native to North America, is a very commonpest, however, after spreading to Eurasian continent, it becomes a very threatening pest to localecology environment, now Fall Webworm occurs in nine provinces in middle and east China,according to reports from State Forestry Administration Forest protection station. The affectedarea increases significantly in the last ten years, reaching1,142,200hectares annually. The statecouncil issued a special notice on Fall Webworm control in year2006.Under history weather conditions, Fall Webworm widely distributes in China, with aestimated suitable area of5.187million square kilometers, which accounting for55%of theland area, a very large area. The EI average value is33.8, distributed in the area of eastlongitude77-134degrees, north latitude9-49degrees, North to Inner Mongolia Yakeshi of49.5degrees north latitude, west to77degrees east longitude Xinjiang da Qi County, and the maindistribution areas locate in middle-east and south west China, including Hainan, Guangdong,Guangxi, Yunnan, Guizhou, Hunan, Jiangxi, Fujian, Zhejiang, Jiangsu, Anhui, Hubei,Chongqing, Sichuan, southern Gansu, Ningxia, Shaanxi, Henan, Shandong, Shanxi, Hebei,Liaoning, Jilin, and southeast of Heilongjiang.CLIMEX is a modeling software predicting the potencial suitable distribution areas of acertain species. The initial parameter values set up according to Fall Webworm’s bioecologydata and the data in CLIMEX model. Based on the prediction of Fall Webworm’s geographicdistribution in the origin area, the parameter values are adjusted till the prediction and realitymatches, and this will be the final parameter values which predicts the geographic distributionin China. After importing the historical weather conditions data and the predictions in future toCLIMEX, working out the EI values of each area respectively, then importing the EI values toArcGIS9.3, with the analysis of Inverse Distance to a Power, making out the distribution chartsof Fall Webworm under the two different weather conditions. The concept of PDD is introduced when CLIMEX predicts Fall Webworm’s potentialdistribution areas, the factor PDD has been considered when calculating the EI values as wellas DD values based on DV0and the climate data of target areas. The ratio of DD and PDD willindicate the generations of Fall Webworm in target areas.Use EHCAM4climate A2, B2, B1, A1FI, the four scenarios to predict the suitable areasof Fall Webworm in China, it is found that the prediction areas are not so different under thefour scenarios, all distributed in the range of75-135degrees east longitude and north tolatitude51degrees, but the area and the degree showing a trend enhanced. The suitable area ofFall Webworm under the four scenarios is5.7million square kilometers,5.81million squarekilometers,6.01million square kilometers and6.09million square kilometers respectively, theincreased area mainly located in Heilongjiang and Inner Mongolia. The average value of EI is22.7,22.8,23.2and23.6respectively.Compared to the suitable history weather conditions, under the assumption of futureclimate warming scenarios, the suitable range of the Fall Webworm in China will furtherexpand, three Longitudes east and westward, and1.5Latitude northward. Inner Mongolia andHeilongjiang will become the critical areas for Fall Webworm. Based on the assumption ofglobal warming, compared to historical weather conditions from low to high, the suitable areaswill expand approximately520,000square kilometers,620,000square kilometers,820,000km2and910,000km2respectively.Under ideal conditions, without considering other biotic or abiotic factors, such as host,climate, natural enemies, Fall Webworm can occur1-8.5generations under history weatherconditions in China, at least two generations in most suitable area, and at least four generationsin the south areas. Among there areas, at least one generation occurs at27-48degrees northlatitude and78-135degrees east longitude,2generations of distribution in the region of26-47degrees north latitude and east longitude82-129degrees,3generations mainly located in thearea of32-41degrees north latitude and105-124degrees east longitude, and4generationscover the range of China southmost to34degrees north latitude and98-123degrees eastlongitude. All has the same trend of generations occurrence under the four different scenarios, justwith a difference in degree.The main difference is the one generation areas will gradually shift to2generation areas,and the3generations areas will expand north and eastward, the four generations areas willexpand under the same range.Compared to the generations under the history weather conditions, Fall Webwormgenerations will expand with the global warming, increasing approximately0.4,0.6,0.8,0.9generations compared to the history weather conditions. And the distribution range also change:one generation a year remains basically unchanged, but the area will increase, from scatteredareas to conjointed ones; the2generations region will expand northward of two latitudes,seven longitudes eastward and six longitudes westward, the distribution area also increased;The3generations distribution range will expand two latitudes northward and one longitudeeastward,18longitudes westward, but the distribution area decreased;4generations or morerange expands six latitudes northward, six longitudes westward with a increase distributionarea.Based on the risk assessment analysis, it is found that all the other provinces will bethreatened by Fall Webworms besides Beijing, Tianjin, Hebei, Liaoning and Shandong,especially the affected areas adjacent to Heilongjiang, Inner Mongolia, Shanxi,Hubei, Jiangxi,Zhejiang, Sichuan, Chongqing and other provinces and cities. Therefore we strongly suggestthat more work like quarantine, monitoring, controlling and propaganda should be done tocontrol the Fall Webworm spreading in China.