| The Siberian crane(Grus leucogeranus)is a nationally protected wildlife species in China and is known as a"living fossil"among bird species.It is listed as critically endangered in the International Union for Conservation of Nature(IUCN)Red List of Threatened Species.Based on its migration routes,it can be divided into three wintering populations:eastern,central,and western.Today,the central and western populations have almost disappeared,and only the eastern population,which winters in China and breeds in Siberia,remains with a population of about 4,000.However,in recent years,the suitable habitat area for the eastern population of Siberian cranes has undergone significant changes due to climate change and human activities,threatening their migration and breeding.Therefore,studying the habitat suitability of Siberian cranes is crucial for protecting rare and endangered species like the Siberian crane and maintaining biodiversity.In this study,based on the different distribution of Siberian cranes,we focused on three aspects:the breeding area(Siberia),wintering area(middle and lower reaches of the Yangtze River),and migration stopover area(northeast and north China).Using MaxEnt modeling and various data sources such as the corresponding distribution sites,vegetation,terrain,and global climate model data(BCC-CSM2-MR,Can ESM5,and CNRM-CM6-1),we simulated the suitable habitat distribution pattern of Siberian cranes and analyzed the relationship between their suitable habitat and various environmental factors.We also used CMIP6 multi-model multi-scenario data to estimate the temperature and precipitation before2060 and analyzed the effects of temperature and precipitation changes on the habitat suitability of Siberian cranes.The main findings are as follows:(1)The MaxEnt model was used to simulate the suitable habitat distribution of the Siberian crane on a global scale.The results showed that the Siberian crane was mainly distributed in the Asian region.A small number of suitable habitats were distributed in the Siberian region of Russia near the Arctic Circle,mainly concentrated near the Kolyma River basin and Lena River basin.There was also a relatively wide distribution of suitable habitats in the central and northern regions of India,centered around the eastern part of Rajasthan and the upper reaches of the Ganges,spreading out in all directions and downstream along the Ganges basin.The most important suitable habitat for the Siberian crane was distributed in the eastern region of China.In the southern region of eastern China,the Siberian crane was mainly distributed in the Poyang Lake area of the middle and lower reaches of the Yangtze River.In the northern region of eastern China,the Siberian crane was mainly distributed in the Songliao Plain in the northeast region.(2)In the breeding area of the Siberian crane,the dominant factors affecting the distribution of suitable habitats are the precipitation in the wettest month(31.8%)and altitude(28.5%).In the wintering area,the dominant factors are the precipitation in the driest month(42.5%)and altitude(40.2%).In the stopover area during migration,altitude(43.9%)and precipitation in the wettest month(19.0%)are the dominant factors affecting the distribution of suitable habitats for the Siberian crane.The contribution of the normalized difference vegetation index(NDVI)factor varies in different study areas.The contribution rates of the NDVI factor in the breeding area,wintering area,and stopover area are 7.5%,2.3%,and 9.2%,respectively,indicating that the degree to which environmental factors affect the distribution of suitable habitat varies in different habitats.(3)Based on the MaxEnt model simulation during the contemporary period(1970-2000),in the breeding area of the Siberian crane,the high suitability zone was approximately 2.40×10~4km~2,accounting for only 0.3%of the total breeding area,while the low suitability zone covered an area of 53.30×10~4km~2,accounting for approximately 6.66%of the total breeding area.In the wintering area,the high suitability zone was 5.47×10~4km~2,accounting for approximately 6.84%of the total wintering area,while the middle and low suitability zones covered areas of 8.15×10~4km~2and 16.59×10~4km~2,respectively,accounting for 10.19%and 20.74%of the wintering area.(4)Between 2021 and 2060,according to scenario projections based on the BCC-CSM2-MR,Can ESM5,and CNRM-CM6-1 models,the suitable habitat areas for the Siberian crane are expected to generally decline.This decline is particularly significant under the SSP5-8.5 scenario,with a clear trend toward fragmentation.Specifically,the high suitability habitat areas for breeding will significantly decrease,while the low suitability habitat areas will increase.Furthermore,the high,medium,and low suitability habitat areas for wintering will all decrease,with a trend towards higher latitudes and higher elevations.However,under the SSP2-4.5 emission scenario,the change in suitable habitat areas for the Siberian crane is relatively small,which is beneficial for the protection of their habitat.(5)According to scenario projections based on the BCC-CSM2-MR,Can ESM5,and CNRM-CM6-1 models,the temperature and precipitation changes between 2015 and 2060indicate that,compared to the wintering area,the breeding area will experience faster and larger temperature increases,but with a decrease in annual precipitation.The temperature in the breeding area is projected to increase by 2.6-5.8℃with an increase of less than 70%,while the precipitation is expected to increase by approximately 25%.The wintering area is projected to experience a temperature increase of 2.4-4.6℃with an increase of around 30%,and average precipitation increased by about 35%.The projections from all three models suggest that the annual temperature and precipitation will increase with the increase of radiative forcing,and that the rapid temperature increase in the future will have a significant impact on the suitable habitat of the Siberian crane,especially in the summer breeding area.Under the SSP5-8.5scenario,the temperature increase is most significant,and precipitation fluctuations are the greatest,resulting in a significant decrease in the high suitability habitat area for the Siberian crane.Therefore,global climate change may have a significant impact on the breeding,wintering,and migration of the Siberian crane.It is crucial to comprehensively assess the survival status of the Siberian crane,understand the impact of various environmental factors on them,and strengthen the protection of their suitable habitats,providing data support and a theoretical basis for the protection and management of endangered species. |
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