Spatial Identification And Conservation Proposals For Roadless Areas In China

Roads are globally expanding at an unprecedented scale,and the spatial extent of road impacts goes far beyond roads themselves.Generally,ecosystem function is significantly inhibited within the road effect zones,recovering as it moves away from the road’s edge.Thus,relatively undisturbed roadless areas are increasingly important.Roadless areas are natural or semi-natural landscapes that represent normal undisturbed ecosystems and have an irreplaceable role in maintaining ecosystem processes,buffering climate change and conserving biodiversity.Although the ecological significance and conservation value of roadless areas have been widely recognized,there is a lack of identification and emphasis on roadless areas in the current conservation framework.China is the most populous country in the world,hosting high biodiversity value and committed to be a rank-top country in terms of transportation scale,quality and greenness,in which identifying roadless areas and their conservation value provides a scientific basis for the effective expansion of protected areas and the optimal layout of road networks.Given this,this study used a combination of machine learning methods and GIS approaches to identify,map and evaluate roadless areas in China.The Normalized Difference Vegetation Index(NDVI)was used as a proxy for vegetation dynamics to indicate the ecological impact of roads.Machine learning methods were used to estimate the effect zones of different level of roads in different geographic areas.Based on the spatial complementary relationships between road effect zones and roadless areas,roadless areas in 2015 and 2018 in China were mapped,and their variation,pattern,conservation value,and vulnerability were evaluated and analyzed.The main research findings are as follows:(1)The threshold of roadless areas in China ranges from 1 km to 20 km,varying by road levels and geographic areas.The total area of roadless areas was 5,597,269.87 km~2 and 5,014,519.54 km~2 in 2015 and 2018,covering about 58.30% and 52.23%of the territory,respectively.Roadless areas mainly distributed in Xinjiang,Tibet,Inner Mongolia,Qinghai,Sichuan,Gansu,Heilongjiang and Yunnan.In general,the total number of roadless areas is increasing while the average area is decreasing,with a clear trend towards fragmentation,especially in Tibet.The landuse of roadless areas is mainly grassland,with an average altitude over 1000 km.In 2018,82.51%(953,957.20 km~2)of the national nature reserves were roadless,accounting for 19.02% of the total area of roadless areas,so there were still about 80% of roadless areas that have not been strictly protected.(2)The conservation value of roadless areas can be roughly divided into four classes.The first class has a high conservation value and mainly includes roadless areas with large patch sizes or located in areas with superior biogeographic backgrounds.The second class is mainly located in the northwest and northeast regions,with some smaller patches of roadless areas in the south also having high conservation value,and a large proportion of the roadless areas in these regions are national protected areas.The third class of conservation value is mainly located in the Tarim Basin and south of the Yangtze River.The fourth class of conservation value is mainly located in the North China Plain,the Inner Mongolian Plateau,and near the Upper Himalayan Mountains.The highest vulnerability of roadless areas are located at the junction of the three provinces of Xinjiang,Tibet and Qinghai,and are also the largest in size,followed by roadless areas on the edge of the big roadless areas in Xinjiang.In addition,roadless areas located in the transition zone between the first and second terraces also have high vulnerability,mainly including those located in Sichuan and Gansu.(3)Roadless areas with high conservation value and high vulnerability are the key areas to be considered for future protected area expansion,which are spatially dispersed,including the southern Tibetan region,the area around the Sichuan Basin,and the northeastern China.Roadless areas with high conservation value and low vulnerability are more widely distributed and numerous,mainly in South China,Northwest and Northeast China.Roadless areas with low conservation value and high vulnerability are mainly located in the North China Plain,the edge of the Inner Mongolia Plateau,and the Sichuan Basin.One of the common features of these areas is the small size of the patches and the high degree of fragmentation.The roadless areas with low conservation value and low vulnerability are basically located in the west,with a concentrated but fragmented distribution.