Impacts Of Historical Climate Change And Human Activities On The Distribution Of Threatened Birds In China

China is one of the countries with the richest biodiversity in the world.But at the same time,species are also facing great risk of being threatened.The intensification of climate change and increasingly human activities are two major factors threatening biodiversity,which will lead to the change of distribution area,population decline or extinction.So far,no studies have assessed the impacts of climate change and human activities on threatened bird distribution in China,especially from a historical perspective.This study based on distribution information of all Chinese birds and threatened birds at the prefecture level,combining the data of climate change(temperature and precipitation)over past 100 years and human activities(forest,cropland,grassland,population density)over past 300 years.Finally,the correlations between the environmental factors and human activity factors and China threatened birds were analyzed.The main conclusions were as follows:(1)This study counted 310 threatened birds in 214 prefectures,accounting for22% of all bird species in China.The distribution of the number and proportion of threatened birds in China showed similar patterns,i.e.,there were more endangered birds in Northern China than in Southern,especially in Northeastern and Northwestern China.(2)The trends of temperature changes in Northern China over the past 100 years were different,i.e.,the first 50 years of coldest month showed a cooling trend,while the last 50 years showed a warming trend.The temperature changes of breeding season were not obvious in first 50 years,but the temperature was rising in last 50 years.The distribution of endangered birds was significantly correlated with temperature changes,while precipitation changes are not significantly correlated.There was a negative correlation between threatened bird distribution and climate changes in the first 50 years but a positive correlation in the last 50 years.These results indicate that the relatively stable temperature in the first 50 years in Northern China may protect the bird diversity in this region,but the rising temperature in the last 50 years may have promoted the increase of endangered birds.(3)The intensify of forest and cropland changes in Northern China was relatively smaller during 1700-1800,especially in Northeast and Northwest China.However,the area of cropland in this region increased significantly in the last 100 years.Notably,the variables with the highest correlation with the distribution of endangered birds are the intensify of forest and cropland changes between 1700 and1800,which means that the regions with less historical land use may have protected the bird diversity.Nevertheless,the increased human activities in these regions in recent 100 years may have caused the increase of endangered birds nowadays.To sum up,our research showed that currently bird diversity in China is facing enormous challenges.The distribution of threatened birds may be affected by climate changes and human activities in different historical periods.The relatively stable temperature and less historical human activities in Northern China may have protected the bird diversity.However,recently dramatic climate changes and human activities may be one of the drivers for the increase of endangered birds.This study comprehensively analyzed the correlations between distribution pattern of threatened birds in China and historical climate changes and human activities,which provided an important scientific evidence for biodiversity conservation in China under the background of global change.