Degradation And Regime Shift Of Wetland Ecosystem In Beijing-Tianjin-Hebei Region In Recent 30 Years

In recent years,due to the rapid improvement of the economic level and the increase in population in Beijing-Tianjin-Hebei region,the irrational use and occupation of wetlands has led to a rapid decline in wetland area and quality,posing a threat to regional ecological security.Under the background of Integrated development of Beijing,Tianjin and Hebei has become one of the three major national strategies,it is required to ensure the quality of the Beijing-Tianjin-Hebei ecological environment to promote regional sustainable development.Ecosystem resilience plays an important role in the maintenance of ecosystem status and services in the context of human activity disturbances and changing natural environments.Therefore,it is necessary to comprehensively assess the status of wetland degradation and use resilience research to provide scientific advice for protecting wetlands and promoting the sustainable development of wetland health.Based on the above situation,this paper quantitatively analyzes the degradation of the Beijing-Tianjin-Hebei wetland from 1980 to 2015 from three perspectives:wetland area,structure and function.Eight river basins(Lower Beishi River Plain,Beishan River Mountainous Area,Ziya River,Heilonggang and Yundong Plain,Daqing River,Yongding River Mountainous Area,Inland River and Luanhe River)are the research units to comprehensively evaluate the degree of wetland degradation;Five typical wetlands of Beijing-Tianjin-Hebei:Anguli Wetland(Bashang Plateau Ecological Zone),Yeya Lake Wetland(Mountain Ecological Zone),Baiyangdian Wetland(Plain Ecological Zone),Beidagang Wetland(Plain Ecological Zone)and Luanhe Delta Wetland(Coastal Sea Ecological Zone)were selected.This paper analysis the regime shift of the typical wetlands through time series regime shift detection.The spatial intensity distribution and the ecosystem characteristics of the key years of the regime shift,and the evaluation of the ecosystem resilience under different steady states of each typical wetland were shown;Finally,this paper analysed the natural and human factors on the degradation of wetland and the resilience changes of the typical wetlands to the scientific restoration of the wetlands.And the major conclusions are as follows.:(1)Wetland degradation in the Beijing-Tianjin-Hebei region is divided into three stages.In the first stage,the structural degradation was dominated in 1980-1995,followed by functional degradation,area degradation.The second stage was in 1995-2009,and the degree of area,structure and function area degradation continued to increase.The degree of degradation is obviously aggravated in 2000-2010.The stage is dominated by functional degradation,followed by structure degradation and area degradation.The third stage is from 2009 to 2015,which is mainly characterized by functional degradation,followed by area degradation and structural degradation.Overall,the comprehensive degradation rates of the Beijing-Tianjin-Hebei wetland in 1995,2000,2009,and 2015 were 13.6%,19.1%,29.1%,and 27.0%.The degree of wetland degradation continued to increase from 1980 to 2009,and it has been reduced from 2009 to 2015.(2)In terms of wetland area degradation,the wetland area in the Beijing-Tianjin-Hebei region generally showed a decreasing trend.From 1980 to 2015,the reduction area was 2,980.60 km2,a decrease of 21.32%,and the reduction of the coastal saline,beaches and marshes was the largest;wetland reduction areas.It is mainly concentrated in the Bohai Sea area of Beijing-Tianjin-Hebei and the Bashang area in the northwest.In terms of wetland structural changes,the changes in the connectivity of the eight basins in Beijing-Tianjin-Hebei can be divided into three types:first decline and then increse,continuous decline,and fluctuation change.In the continuous decline type,the connectivity of the wetland wetland decreased as much as possible from 1980 to 2015.41.8%;through the type level and landscape level landscape index,it shows that the landscape fragmentation of the Beijing-Tianjin-Hebei wetland is enhanced and the shape of the wetland become simple.In terms of the functional degradation of habitats provided by wetlands,the suitable habitat area of the wetland as the main waterfowl in Beijing and Tianjin has decreased by 45.0%in the past 30 years;the area of low suitable area is the most obvious.(3)Two or more regime shift occurred in each typical wetland in the past 30 years,and the number after 2000 were greater than before 2000.For the characteristics of the typical wetland regime shift years,different typical wetlands have happened different water and vegetation changes,and the steady-state transition has obvious hysteresis effect,which is obviously affected by the precipitation or water accumulation in the early stage.The wetland in typical plain ecological zone is affected by artificial hydration,and the wetland in the coastal and marine ecological zone greatly affected by artificial farming.(4)The resilience level of each typical wetland is:Yeya Lake>Baiyangdian>Beidagang>Luanhe Delta>Anguli.The typical wetland resilience shows a continuous downward trend in the Bashang ecological zone and coastal sea ecological zone where the ecological environment is relatively fragile.while in the plain ecological zone with the strongest human activity,the typical wetland resilience shows volatility under human disturbance.Due to wetland protection measures and relatively few human disturbances in the mountainous ecological zone,the resilience change of typical wetlands is relatively stable.(5)The occurrence and development of the degradation of the Beijing-Tianjin-Hebei wetland is mainly affected by social and economic factors,followed by natural factors.In terms of social economy,the rapid population growth in the Beijing-Tianjin-Hebei region in the past 30 years has increased the demand for food,resulting in the continuous encroachment of cultivated land and construction land to wetlands.At the same time,the construction of watershed projects has reduced the seasonal inundation area.A large number of wetlands have been lost and the fragile wetland ecosystem has been severely damaged.The surface water and groundwater reserves of Beijing-Tianjin-Hebei were mainly declining from 1980 to 2015,and it had a negative impact on the degradation and natural restoration of wetlands.The characteristics of the warming and drying of the regional climate have gradually reduced the wetland area,especially for the Bashang area where the precipitation is less,and it has accelerated the degradation of the wetland.The implementation of the wetland protection project has alleviated the degree of wetland degradation,which has enabled the ecological resilience of the wetland to be maintained or rebounded.