The Impact Of Land Use Transition On Vegetation Carbon Sequestration In China

The global warming caused by the surge of carbon emissions poses a serious threat to the sustainable development of human society.The beautiful vision of a carbon-free future makes carbon neutrality increasingly become the strategic appeal of many countries.The Chinese government has announced the strategic goal of achieving carbon peak by 2030 and carbon neutrality by 2060.Since the “doublecarbon” strategy was proposed,China has taken rapid action to reduce carbon emissions and fulfill its the “Paris commitment” as scheduled.However,there are still many practical challenges in carbon neutrality.The key is to maintain a dynamic balance between carbon emissions and carbon absorption,and realize the “net zero emissions” in the society.As an important part of ecological carbon sequestration system,terrestrial vegetation plays an important role in increasing carbon absorption.Compared with artificial carbon sequestration,vegetation carbon sequestration has the unique advantages of low economic cost,high social benefits,large carbon sequestration potential and strong sustainability.In the context of continuous progress of “double carbon” strategy,vegetation carbon sequestration will become an important ecological tool for realizing the long-term development goal of carbon neutralization.However,land use change has become an important cause to change terrestrial biomass production,carbon source and carbon sink.Most of the essential causes of a series of eco-environmental problems in our country point to the rapid change and irrational use of land.It is urgent for the government to adjust the layout of land use and speed up the transformation of land use.Therefore,clarifying the relationship between land use transition and vegetation carbon sequestration is of great significance for the formulation of specific action plans for carbon neutrality.Focusing on vegetation carbon sequestration,this paper explores the impact of land use transition on vegetation carbon sequestration in China from external and internal paths based on the basic analysis framework of land use transition theory.Furthermore,taking cropland protection as an example,the impact of land use transition under policy intervention on vegetation carbon sequestration was discussed.Therefore,the main research contents are as follows:Firstly,combined with satellite remote sensing data,GIS spatial analysis technology was used to calculate the vegetation carbon sequestration data of district and county length series and multiple land use types in China from 2000 to 2020.The temporal variation trend and spatial distribution characteristics of vegetation carbon sequestration were presented by visualization technology,and the differences between the measured results were compared.Secondly,in the external transition path,the index decomposition method was used to quantify the impact of carbon sequestration efficiency and scale change of different land use types on vegetation carbon sequestration at the district and county level from 2000 to 2020,and further combined the characteristics of external form of land use “ebb and flow” and the heterogeneity of vegetation carbon sequestration.The scenario analysis method was used to simulate the possible evolution trend of vegetation carbon sequestration in China in the next 5 and 10 years.Thirdly,in the internal transition path,based on the special theoretical perspective of human appropriation of vegetation net primary productivity,the impact of agricultural land intensification on vegetation carbon sequestration during2000-2020 at the prefecture-level cities was explained by panel econometric model.In the empirical analysis,instrumental variable was used to control the possible endogeneity problems,and a variety of testing methods were tried to increase robustness.Furthemore,the impact of vegetation carbon sequestration of appropriation and its potential risks were further discussed at the provincial level.Finally,with the strict cropland protection policy as the foothold,this paper analyzes how the strict cropland protection policy maintain the quantity and quality stability of cropland by combing the long-term development context of policies,and expounds the mechanism of its influence on vegetation carbon sequestration.On this basis,the cropland quantity target of prefecture-level city was taken as a quasinatural experiment,the cropland red line constraint index was constructed,and the differential difference model was used to verify the growth effect of vegetation carbon sequestration under the cropland red line constraint and its mechanism.The main conclusions are as follows:Firstly,vegetation carbon sequestration in China presents a trend of fluctuation and rise.Woodland was the main source and contributor to growth,followed by cropland and grassland.The spatial characteristics are high in the northeast and southwest,and low in the middle and northwest.By comparing the calculation results,it can be found that the difference of vegetation carbon sequestration of different products mainly comes from classification system rather than precision.Even if this paper resets the product classification system and matching relationship at a higher dimension,the identification deviation is still inevitable,and the subdivision type is even larger.However,different classification systems also provide diverse options for the study of vegetation carbon sequestration.Secondly,the growth of vegetation carbon sequestration in China is mainly attributed to the improvement of the efficiency of land carbon sequestration.The scale of ecological land has a “base” effect,but the inhibition effect of scale reduction on the growth of vegetation carbon sequestration has begun to emerge.The decomposition results at the district and county level are consistent with those at the national level,but the effect of land carbon sequestration efficiency has temporal and spatial heterogeneity.The results of scenario analysis show that,compared with 2020,the total amount of vegetation carbon sequestration in China will increase by 4.4% in 2025 and 8.9% in 2030 under the natural scenario.The relative optimal scenario increases further to 7.9% and 12.6%,but this is the ideal condition.In the relative worst scenario,the total would fall by 7.2% and 3.1%.Thirdly,under the dual influence of controlling natural and social factors,agricultural land intensification in prefecture-level cities has a significant driving effect on vegetation carbon sequestration.This conclusion is still supported under many robust conditions,and the use of city distance as an instrumental variable effectively alleviates the possible endogenous bias.However,the results of instrumental regression also imply that the improvement effect of land intensification may be underestimated.Further discussion shows that land intensification also increases the scale of appropriation of vegetation carbon sequestration,which leads to increased potential risks to ecosystem stability and sustainability.However,due to the lack of specific threshold value of ecological overspending,the measurement of its potential risk is only a characterization of the data.Meanwhile,due to the limitation of data sources,the discussion is limited to the provincial level.Fourthly,the strict red line constraint of cropland significantly improved the vegetation carbon sequestration.However,this positive effect has a one-year lag,and the policy effect shows a trend of rising fluctuation to gradually decreasing and then flattening.This may be directly related to the fact that local governments overused the cultivated land quantity target when the red line constraint of cropland was relatively loose,which gradually increased the constraint in the later period,forcing the central government to moderately relax the cropland constraint target.The above conclusions are confirmed under a variety of robust conditions.Further discussion showed that land use transition significantly enhanced the growth effect of vegetation carbon sequestration under the red line constraint of cropland,but the impact degree was relatively small.It may be caused by the small scale of land conversion during the study period,or other mechanisms.The innovation of this paper mainly includes the following three aspects:(1)The innovation of research perspective.This paper focuses on vegetation carbon sequestration.Based on the basic analysis framework of land use transition theory and satellite remote sensing data,the effects of land use transition on vegetation carbon sequestration in China were revealed from external and internal transition paths.The impact of the “quantitative change” characteristics of land use transition was discussed in the external path,focusing on the change of land carbon sequestration efficiency and land scale,and extended to the future evolution trend.In the internal path,the impact of the “qualitative change” characteristics of land use transformation was explored,and the promoting effect of agricultural land intensification was investigated.The increasing effect of vegetation carbon sequestration by the strict cropland protection policy was demonstrated(2)The innovation of research data.To meet different research needs and application scenarios,this paper combined a variety of satellite data products to calculate the long-term time series and multi-land use types of vegetation carbon sequestration data in China.Detailed data on vegetation carbon sequestration can extend the research on carbon neutralization to the county scale,and the information of different regions can also be deduced from the bottom up.Meanwhile,according to the characteristics of the data products provide the user with the appropriate choice scheme.It not only fills the deficiency of the basic data of vegetation carbon sequestration in existing studies,but makes up the weakness of the authenticity and accuracy of the traditional measured data.(3)The innovation of research content.(1)In terms of influence mechanism,this paper combined the “quantitative change” and “qualitative change”characteristics of land use form to clarify the impact of land use transition on vegetation carbon sequestration.In the process of “quantitative change”,land scale and land carbon sequestration efficiency were incorporated into the same decomposition framework,and the main causes affecting vegetation carbon sequestration growth were identified at the district and county level.In the process of “qualitative change”,based on the perspective of human appropriation of net primary production,the positive effect of land intensification on vegetation carbon sequestration was discussed at the prefecture-level city level.(2)In terms of the evaluation of policy effects,this paper takes the strict cropland protection policy as an example and explores how local governments maintain stable quantity and quality of cropland in the “top-down and multi-level decomposition” mandatory management through the analysis of institutional background and mechanism,so as to create conditions for the growth of vegetation carbon sequestration.In the empirical analysis,the cropland red line constraint index was constructed of prefecture-level cities to depict the cropland constraint pressure faced by local governments,and the continuous differential model was used to test the impact of the strict cropland protection policy on vegetation carbon sequestration and its mechanism.