Impacts Of Climate Change And Human Activities On The Potential Distribution Of Invasive Plants And Identification Of Risk Areas

The invasion of alien plants poses serious threats to local ecosystems and biodiversity. Climate change and human activity affect plant invasion simultaneously.Yunnan, a province located in the southwest of China, is not only one of the biodiversity hotspots, but also an area with seriously disturbing of invasive plants. In this paper, with occurrence records and environmental factors including climate change, human activity,soil characteristics, hydrology and topography, based on MaxEnt software, the combination of China climate niche model and regional environment niche model was applied to analyze the effect of climate change and human activity on the potential distribution of eight invasive plant species in Yunnan Province. Zonation was combined with the results from niche models to identify priority areas with high invasion risk for monitoring. This will provide decision support for preventing and controlling the spread of invasive plants, and therefore decreasing the negative impacts of climate change,human activity and plant invasion on biodiversity in Yunnan Province. The results showed that:(1) The most important factors influencing the potential distribution of invasive plants in Yunnan Province were climate suitability (permutation importance, 43.4%)and human activity (40.4%, including landcover (17.1%), human influence index(14.8%) and distance to crops (8.5%)).(2) The importance and effects of environmental factors differed obviously among invasive plant species. Climate suitability was the most important factor influencing the potential distribution of Mikania micrantha, Tithonia diversifolia, Chromolaena odorata, Ageratina adenophora and Ageratum conyzoides. As climate suitability increased, the relative occurrence probability of invasive plants increased gradually.However, when climate suitability >0.7, the occurrence probability of Ageratina adenophora decreased slightly. Landcover was the most important factor influencing the potential distribution of Conyza sumatrensis and Alternanthera philoxeroides. The relative occurrence probability of Conyza sumatrensis was dramatically higher in built-up areas. The probability of Alternanthera philoxeroides was significantly higher in built-up and aquatic areas. Human influence index was the most important factor influencing the potential distribution of Parthenium hysterophorus. With an increase of human influence index, the occurrence probability of Parthenium hysterophorus increased in the form of s-shaped curve.(3) Under current climate conditions, climate suitability of invasive plants.decreased gradually from south to north, and regions with high climate suitability were mainly distributed in the south, where altitude was low and climate was warm and humid. Plant invasion risk increased gradually from north to south and from east to west. Invasion risk was generally high in the south regions with high climate suitability.Besides, it was also high in some regions with low climate suitability, such as Erhai Lake Basin,Dianchi Lake Basin and Fuxian Lake Basin. Under future climate scenarios,climate suitability would decrease in the south while increase in the north, and invasion risk decrease in the south while increase in the east. Consequently, regional difference of climate suitability and invasion risk of alien plants would decrease in Yunnan Province under climate change.(4) The area of high invasion risk region was 77946km2, which occupied 20.4%of the study region. The high-risk region was mainly distributed in the west and south of Yunnan Province, such as Dehong Prefecture, Nujiang River valley and Yuanjiang River valley, low altitude area in Lincang City, the south of Puer City, the middle and south of Xishuangbanna Prefecture, Honghe Prefecture and the south and east of Wenshan Prefecture. Besides, Erhai Lake Basin, Dianchi Lake Basin and Fuxian Lake Basin were also in high invasion risk. According to landcover in high-risk region, we concluded that croplands, built-up and aquatic areas suffered plant invasion most seriously. The geographical distribution center of high-risk region was predicted to move towards areas with higher latitude and altitude under future climate scenarios.The area of high-risk region within nature reserves was 3185km2, which occupied 14.9%of the nature reserves. The high-risk region was mainly distributed in nature reserves located in the west and south boundary of Yunnan Province, such as Tongbiguan,Xishuangbanna, Huanglian Mountain and Dawei Mountain Nature Reserves. Besides,Erhai Lake Nature Reserve was also in high invasion risk.The results provide theoretical basis for pointedly taking effective measures to prevent, monitor and renovate plant invasion for biodiversity protection in Yunnan Province.