基于随机森林模型预估气候变化对动物物种潜在生境的影响

Assessment of Effect of Climate Change on Potential Habitat of Animal Species Based on Random Forest Model

以白冠长尾雉(Syrmaticus reevesii)、中华穿山甲(Manis pentadactyla)和藏酋猴(Macaca thibetana)这3种动物作为研究对象,采用当前(1950—2000年)、2050年和2080年3个时期的气候数据,利用随机森林模型预估气候变化对动物物种潜在生境的影响。其中,2050和2080年的气候数据由3种大气环流模型(MIROC32-medress、CCCMA-CGCM2和BCCR-BCM2.0)和1个温室气体排放预设情景(SRES-A2)下2050和2080年的气候数据进行平均后得到。每一时期的气候数据包含19个生物气候因子,将19个生物气候因子全部作为环境变量,通过随机森林模型分别模拟并预测这3种动物在当前气候条件下的潜在生境,以及未来2050和2080年气候条件下的潜在生境,并用潜在生境质心(centroids)的位置变化来表征物种潜在生境的偏移情况,分析潜在适宜生境面积及物种最适宜海拔高度的变化,采用受试者工作特征曲线和真实技巧统计值评价模型的预测精度。结果表明,3种动物的潜在生境逐渐向北偏移,最适宜海拔高度逐渐升高。其中,中华穿山甲潜在生境的北移速度最快,至2080年北移量达133 km;白冠长尾雉的最适宜海拔高度上升最快,至2080年上升152 m。3种动物的潜在生境面积均逐渐增加,白冠长尾雉的增幅最大。建议在动物保护行动中考虑气候变化对物种的影响,制定长期的保护策略。

Species distribution models are widely used to assess the effects of climate change on species distribution.Random forest （RF） model is a relatively novel machine learning method among species distribution models,quite high in accuracy.To use the method to assess effects of climate change on potential habitats of animal species,three animal species,Syrmaticus reevesii,Manis pentadactyla and Macaca thibetana,were selected as research subjects and the meteorological data of 2050 and 2080 were figured out with the aid of the three atmospheric global circulation models （GCM）,i.e.MIROC32-medress,CCCMA-CGCM2 and BCCR-BCM2.0 and a greenhouse gas emission default scenario （SRES-A2）.The climate dataset of each period consists of 19 bio-climatic factors,which were all cited as environment variables for the random forest model to predict potential habitats for the three species of animals under the current climate conditions and in the two future time periods （2050 and 2080）,characterize shifts of the potential habitats of the species with movement of the potential habitat centroids in position,and analyze changes in area and altitude of the potential suitable habitats of the species.At the end,prediction accuracy of the model was evaluated with the receiver operating characteristic （ROC） curve and the true skill statistics （TSS） methods.Results show that the potential habitats of the three species would move gradually northwards and upwards in altitude.Among them,Manis pentadactyla＇s would move the fastest and in 2080 it would reach as far as 133 km up to the north,while Syrmaticus reevesii＇s would move upward in altitude the fastest and in 2080 it would be 152 m higher than the current.Besides,the potential habitats of all the three species would gradually expand in area,with Syrmaticus reevesii＇s expanding by the largest margin.It is,therefore,suggested that the impact of global climate change on species should be taken into account in develop long-term protection strategies for wild life.