Land Use/Cover Change And Its Impact On Carbon Storage In Hainan Island Coastal Zone

As a special transition zone between land and sea,coastal zone is a typical wetland ecosystem with unique functions.However,due to long-term Marine and terrestrial interference,especially the accelerated development of urbanization and the increasing expansion of human activities,the structure and functional surface of the coastal zone ecosystem have been seriously damaged.The deterioration of regional ecological environment quality has become an obstacle to the economic and social development of coastal zones,and this problem is attracting more and more attention.Based on this,this study took the coastal zone of Hainan Island as the research object,takes the multi-temporal land use data from 1990 to 2020 as the main data source,and used Arc GIS and InVEST model to explore the spatio-temporal evolution of regional land use and its response to carbon storage in the past 30 years.Then studied the effects of complex land use change processes on carbon sink services in tropical and subtropical coastal zones.The"top-down"macro-control and"bottom-up"SD-FLUS models were constructed to explore the characteristics of multi-scenario land use change and its impact mechanism on ecosystem carbon stocks under different scenarios in the future.In order to reveal the effects of future multi-scenario land use change on regional carbon sources and sinks.It can provide scientific basis and theoretical basis for optimizing land use structure,rational utilization,planning and decision-making in coastal zone,and provide technical support and scientific basis for realizing regional sustainable development.(1)The land use structure of the study area in 1990,2000,2010 and 2020 is dominated by forest land and cropland in the current pattern.Forest land occupies the dominant position,with the area proportion accounting for 39.20%,39.73%,39.04%and 37.81%of the total area respectively,showing a trend of rising and then declining.Arable land occupies the second position,with the area proportion of 27.28%,26.77%,26.30%and 25.34%of the total area,showing a continuous decreasing trend.The rate of change of grassland area was divided into-15.97%,-8.48%and 2.65%,showing a decreasing and then increasing trend,with an overall decreasing trend.The overall rate of change of water area is 173.71%,showing a trend of increasing and then decreasing.The area of construction land increased year by year,with annual change rates of 3.12%,3.49%and 5.47%respectively.The proportion of unused land to the minimum area.(2)From 1990 to 2000,the largest area transformation map was"grassland→forest land",accounting for 30.74%of the total area of the transfer map.From 2000 to 2010 to2020,the conversion of land use type was mainly concentrated among cultivated land,forest land and construction land.From 2000 to 2020,"cropland(forest land)→built-up land"is the main land conversion type.Haikou City and Sanya City are the main places where land use change is drastic.(3)In 1990,2000,2010 and 2020,the carbon stocks in the study area were 4.36×10~7 t,4.3×10~7 t,4.22×10~7 t and 4.21×10~7 t,showing a continuous decreasing trend.In the past 30years,the carbon stocks in the study area were most significantly changed to"unused land→grassland",reaching 1.25×10~5 t."Forestland→grassland"followed,with 1.06×10~5 t.The mangrove and wetland areas in the southwest and northeast of Hainan Island are high-high concentration areas of carbon storage.The ocean is a low-low concentration area of carbon storage.(4)The most significant reduction of carbon storage was grassland→forest land(plantation forest),which was 5.68×10~5 t.It was followed by"grassland→water area",which was 3.62×10~5 t.From 1990 to 2000,"grassland→forestland(artificial forest land)"accounted for the largest proportion of regional carbon storage reduction,and from 2000 to2010,"grassland→water area"was the most significant change of carbon storage reduction.From 2010 to 2020,"forest land→built-up land"is the most obvious map change of carbon storage reduction.Unreasonable human activities lead to dramatic changes in regional carbon stocks,and the influence of human factors on carbon stocks increases.(5)In the three prediction scenarios from 2020 to 2030,forest land was effectively protected and its area increased only in the ecological priority scenario.Construction land expanded to different degrees in the three prediction scenarios.The growth rate was the largest in the development priority scenario.Under baseline and priority scenarios,regional carbon stocks decreased by 1.29×10~5 t and 2.45×10~5 t,respectively.Under the ecological priority scenario,the carbon sequestration capacity was increased by 1.34×10~5 t,and the decrease of cultivated land area was controlled effectively.Therefore,it is urgent to strengthen the integrated and coordinated management of land use.In order to improve the current land use policy more comprehensively and achieve the carbon target.