Soil Erosion Prediction In Red Soil Area Of Southern China Based On Trade-off Between Soil And Water Conservation And Agriculture Development

Soil erosion is the leading factor of land degradation,which in turn threatens food security.In recent years,China has implemented ecological projects on a large scale to control soil erosion,and soil erosion has shown a continuous reduction in area and a significant decrease in intensity.However,under the new erosion environment and social demands,the focus of soil erosion control should shift from comprehensive management to ecological regulation,with the main focus on enhancing ecological functions and seeking synergistic ways for sustainable development of soil and water conservation and agriculture.Soil and water conservation and agricultural development have complex reciprocal feedbacks,and revealing the intrinsic correlation between them can help to better predict future soil erosion patterns and provide scientific basis for national ecological civilization construction.This paper analyzes the pattern of soil and water conservation in the southern red soil zone from 2000 to 2020 using the CSLE model and soil and water conservation bulletin data;constructs the assessment system of agro-ecological subsystem and agro-economic subsystem in the study area by the integrated index method,and further evaluates the development status of the coupled agro-ecological-economic system by using the coordination degree,revealing the development trend of agriculture in the study area in the past 20 years;on the basis of the above results,the multi-year average of the coordination degree of agro-ecological-economic system in 69 cities in the southern red soil area was classified,and the inner relationship between different conditions of agricultural development and soil and water conservation was analyzed;the relationship between the two was considered comprehensively and used as a constraint to predict the soil erosion pattern in 2050 in the southern red soil area under different development scenarios（natural development scenario and sustainable development scenario）,aiming to provide a reference for soil and water conservation and The paper aims to provide reference for soil and water conservation and ecological environment construction in the region.The main results of this paper are as follows:（1）The analysis of soil erosion modulus results and soil and water conservation bulletin data shows that soil erosion in the southern red soil area has been effectively controlled in the past 20 years.77647.91 km² of soil erosion area was reduced from 2000to 2020,of which 55111.10 km²was reduced by mild erosion,accounting for 70.98%of the total reduced area.Secondly,the erosion control area increased from 104446.3km²in2000 to 224006.2 km² in 2020,and the total control area reached 119559.9km²in the past20 years,accounting for 18.37%of the total area;the erosion control efforts and the erosion control area showed a simultaneous increase,and the spatial characteristics showed a gradual increase from southwest to northeast,which is related to the regional natural conditions and the investment in soil and water conservation.（2）In the past 20 years,the agricultural development status of the southern red soil area has improved year by year and showed a spatial divergence pattern,with the southeast coastal cities developing better than the northern inland areas.The evaluation results of agro-ecological and agro-economic subsystems show that the development level of both subsystems is gradually improving in a stable manner,with the evaluation index of agro-ecology increasing from 0.53 to 0.56 and that of agro-economy increasing from0.15 to 0.24 during the period of 2000-2020.The evaluation results based on the coupled coordination model show that the coupling degree of the coupled agro-ecological-economic system has been at a high level,and the coordination degree increases linearly with time;the spatial coordination degree is high in the southeastern coastal cities and low in the northern regions.These results indicate that the northern region needs to increase investment in agricultural development,uphold the concept of sustainable development,focus on ecological protection,and realize rural revitalization.（3）The results of Granger causality test and empirical analysis show that soil and water conservation and agricultural development have a mutually reinforcing relationship in the past 20 years,but their relationship is limited by the degree of coordination of the agro-ecological-economic system.According to the results of the classification of the multi-year average of the coordination degree from 2000 to 2020,there are 69 cities in the southern red soil region,among which 11 cities are at the stage of near disorder,where soil and water conservation promotes agricultural development;45 are at the stage of barely coordinated,where soil and water conservation and agricultural development are mutually driven;13 cities are at the stage of primary coordination,where agricultural development drives soil and water conservation development.（4）Based on the results of climate and land use simulations,this paper predicts the soil erosion conditions in the southern red soil region under different development scenarios（natural development&sustainable development）.The results are as follows:compared with the soil erosion in the past 20 years,the average soil erosion modulus in2050 increases significantly,which may be related to the extreme rainfall events in the future;the soil erosion modulus under the sustainable development scenario is 876.56t·km^-2·a^-1,which is 99.19 t·km^-2·a^-1 less than that of the natural scenario.The optimization of land use structure and spatial pattern is conducive to reducing the risk of soil erosion.