| In the context of global change,the shift in land use from natural areas to agricultural and human settlements has caused habitat disturbance,leading to habitat fragmentation and habitat marginalization,which in turn has led to a global loss of species diversity.According to relevant estimates,globally monitored wildlife populations decreased by an average of 68%between 1970 and 2016.With current national and worldwide trends of increasing land development and ecological footprint,the impact of habitat change on biodiversity will further increase in this century.Related projections indicate that by 2070,approximately 1700 species are at risk of extinction due to habitat area reduction alone,accounting for approximately 8.7%of Terrestores,mammals,and amphibians monitored globally.How to maintain the sustainability of species habitats and thus conserve species diversity is a key theoretical and practical issue worldwide.Shanghai,a mega-city in the Yangtze estuary region,has expanded its urban land area by 400%between 2000 and 2020.During the urbanization process,the Yangtze estuary has become one of the most severely impacted areas of human activities in the world due to the high intensification of human activities and the pursuit of high land values,and the drastic land cover changes.The overlap of land development areas and biological preference areas will increase the impact of human activities on species’habitats.Birds,as indicator organism that is more sensitive to the response of environmental changes,can reflect the impact of habitat changes in an integrated manner.In the context of urbanization,is the area of bird habitat in the Yangtze estuary on an increasing or decreasing trend in the past and at the present stage?What is the future situation?If sustainable habitat management is the goal,how should measures to balance future regional development and bird habitat conservation be determined?These are the core questions that this study will focus on.This paper systematically analyzes the species,abundance,and spatial distribution of six major ecological groups of birds in the Yangtze River estuary in 2020,explores the important environmental factors affecting the presence/absence of birds in the Yangtze River estuary,and predicts future scenarios based on historical data of important environmental factors.Based on the presence data of birds in six ecological groups and the data of important environmental factors in the past,present,and future,we simulated the distribution of birds and explored the spatial and temporal evolution of suitable habitats and population response trends of birds in the context of urbanization.Finally,the expressions of bird habitats in the Yangtze River estuary were obtained based on logistic regression analysis,as well as hotspots for bird conservation and management in the Yangtze River estuary based on comparative spatial analysis,and provide solutions for the construction and optimization of priority conservation and management areas.(I)Study on the distribution of birds in the Yangtze River estuary and their influencing factorsBased on the presence/absence data and potential influencing factors(meteorological data,land use distance data,and socio-economic data)of six ecological taxa(Terrestores,Raptatores,Passeres,Grallatores,Natatores,and Scansores)in the Yangtze River estuary,we used typical correlation analysis to screen the important environmental The linear relationship between bird presence/absence and important factors was explored.The results showed that the presence/absence of birds in each ecological group was significantly correlated with the distance from each land use type in the Yangtze River estuary,and the important factors affecting the presence/absence of each ecological group were related to their habits.The distance to farmland,wetland,urban greenland,urban build-up,bare land,and water were the most important factors influencing the distribution of birds in the Yangtze River estuary at 99%confidence level,and the cumulative contribution of the six environmental factors was>90%.The cumulative contribution of the six environmental factors is>90%.(II)Spatial and temporal evolution of land use in the Yangtze River Estuary from2000 to 2037After determining the important influencing factors of bird habitat in the Yangtze River estuary,the PLUS model was used to predict its future scenarios and analyze its spatial and temporal evolution and development trend to provide data support for bird habitat research.The results show that(1)urban build-up,farmland,and water are the main land use categories in the Yangtze estuary from 2000 to 2037,and the landscape characteristics in the study area have changed profoundly,especially urban build-up and farmland;(2)the Yangtze estuary region mainly meets the demand for urban expansion by occupying farmland to meet the demand for urban expansion,resulting in a continuous increase in built-up land area,which increased by 6243 km~2,while farmland decreased at a similar rate,decreasing by 6333 km~2;(3)during 37 years,the land use/land cover of the Yangtze estuary continued to fragment and complicate;(4)2010 was a more critical year,with land use area changes,the spatial pattern changes were different before and after 2010.The four periods(2000-2010,2010-2020,2020-2029,and 2029-2037)show a trend from fast to slow.(III)Bird habitat simulation and conservation management in the Yangtze River Estuary from 2000-2037Based on bird presence data and land distance data,the Maxent model was used to simulate the distribution of birds in the Yangtze River estuary,analyze the evolution of spatial and temporal patterns of suitable habitats,important influencing factors,and linear relationships between suitable/non-suitable bird habitats and important influencing factors,and explore bird conservation hotspots and future regional development strategies for bird conservation purposes.The results of the study show that(1)urban construction and farmland are key factors influencing bird habitat.The habitat change of birds was positively correlated with farmland change and negatively correlated with urban build-up area change,and the buffer zone 300 m away from urban build-up was the key area for bird habitat maintenance and protection.The expression of the linear relationship between suitable/non-suitable and distance from farmland and urban greenland for overall bird habitat in Yangtze estuary:ln(p/(1-p))=-0.017*Dist＿farmland-0.001*Dist＿greenland+6.696.(2)In terms of ecological groups of birds,around 2010,the area of bird habitat for each ecological group changed dramatically around 2010.The trend of change in the area of suitable habitat for birds of all ecological groups except Raptatores and Scansores shifted from increasing to decreasing.the outlook for Scansores is relatively optimistic,but for Terrestores and Natatores groups,the habitat almost disappears after 2029.Future management of Terrestores and Natatores habitat should be prioritized.For Terrestores,the creation of new green spaces in nearby suburban areas as ecological corridors for birds is necessary.For Natatores,it is necessary to optimize the land use type at the edge of the watershed,and the land use type of farmland is superior to built-up areas,and maintaining or increasing the area of water and farmland ecotone will help protect Natatores.(3)In terms of overall spatial and temporal changes in bird habitat,the bird habitat of each ecological group in the Yangtze River estuary region tends to be fragmented and complex between 2000 and 2037,with increasing spatial overlap,and the proportion of suitable area decreases from 66%to 45%,a decrease of about 4340 km~2,with a smaller and smaller habitat area.Future interspecific competition is increasing and suitability is decreasing.There is an urgent need to increase crop structural diversity and crop diversity within existing habitats in order to maintain or increase bird populations in the Yangtze estuary with highly intensive agricultural processes.(4)Control with bird habitat as the core objective should not only focus on national nature reserves but also bird habitats in Chongming,Jinshan,Fengxian,Pudong,and Taihu Lake areas,especially those within 300 meters of built-up areas,need to be managed and protected as a priority.For Chongming bird habitats with diverse ecosystems,increased protection efforts are needed to reduce or even avoid further fragmentation of bird habitat patches,and to maintain or even increase their patchy connectivity by increasing green areas.Bird habitats in other areas need to increase the connectivity of habitat patches by establishing bird corridors,such as establishing and protecting multi-level vegetation structures. |
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