Research On Identification And Evaluation Of Critical Ecological Spaces In The Dongjiang River Basin

The Dongjiang River Basin has been one of the most important parts in the Pearl River Delta in Guangdong Province,southern China.But the ecological environment of the river basin has been regional fragile in recent years,due to the frequent soil erosion.It is a high demand to identify the critical ecological spaces for the environmental security in the sustainable development of the main ecosystem.In this study,an evaluation system was constructed to quantitatively reveal the distribution characteristics of the critical ecological space from2000 to 2020 using importance and sensitivity.Five aspects were selected to identify the regional critical ecological spaces,including the water conservation function,soil and water conservation function,biodiversity function,soil erosion sensitivity,and geological hazard sensitivity.Specifically,an evaluation model was established to fully meet the typical red soil in the ecologically vulnerable areas.We constructed a local evaluation index system to accurately identify the critical ecological space using the NPP(Net Primary Production)quantitative evaluation.A comparative analysis was carried out to verify the accuracy of the identification using Google Earth images and the territorial spatial planning data of the cities and counties in the study area.Finally,the distribution of various critical ecological spaces was explored for the ecological security of land use.The results showed that:(1)The importance of the comprehensive service functions of the ecosystem in the Dongjiang River Basin was relatively balanced,and the overall service functions were relatively strong.From the perspective of spatial distribution,it showed that the lower reaches< upstream < middle reaches;the comprehensive sensitivity of the ecosystem in the Dongjiang River Basin was mainly sensitive,and from the perspective of spatial distribution,it showed that the middle reaches < upstream < downstream.(2)From 2000 to 2020,the critical ecological spaces in the Dongjiang River Basin were mainly distributed in the middle and lower reaches,among which the urgent ecological space was mainly distributed in various nature reserves and scenic spots,which was more consistent with the ecological conservation redline space in national land space planning;while the crisis ecological space was mainly distributed the downstream developed cities.The crisis ecological space was mainly distributed in the lower reaches of the Dongjiang River Basin,around the urgent ecological space,and was relatively close to the area of human activities.(3)From 2000 to 2020,the critical ecological space in the Dongjiang River Basin showed a trend of decreasing by 1% every 10 years,and the urgent ecological space was almost unchanged,which was mainly reflected in the crisis ecological space,and the crucial type of non-critical ecological space and suitable for development has changed.The crisis ecological space,a crucial ecological space or suitable development ecological space,the change areas were mainly located in the areas with frequent human activities in the upper,middle,and lower reaches of the Dongjiang River Basin and around the construction land.(4)The increase in ecosystem services mainly occurred in the areas where the forest area increased and the construction land decreased,while the ecosystem sensitivity was the opposite.A large part of the construction land and cultivated land occupies critical ecological space,and they were concentrated in the crisis ecological space.The land types of each ecological space were mainly forest land and cultivated land.When land use was relatively tight,crucial ecological space can be effectively used.In the past 20 years,the proportion of construction land and cultivated land occupying critical ecological space has increased,but the overall change has not changed much,it showed that the development boundary of the river basin can be strictly controlled when urban construction land and cultivated land were developed,and the critical ecological space can be effectively protected.