Environmental Risk Warning Of The Intensitive Agricultural Land Use Based On Material Flow Analysis

Facing the increasingly scarce of agricultural land resources and rising food demand, the intensive agricultural land use pattern has become an important measure to increase the agricultural production. However, the environmental risk induced by intensive agricultural land use has become a significant problem, which affects both the social economic development and livelihood. Therefore, this dissertation used the material flow analysis, the environmental risk pre-warning theory, the landscape ecology theory and the scenario analysis method to analyse the agricultural land use systematically, taking the important grain producing area in China——Dongting Lake basin as an example. Along the thought of "analyzing the material flow of the agricultural land use system——evaluating the environmental risk and influence factors——pre-warning of the environmental risk in the future——preventing the environmental risk based on moderate intensification of agricultural land use", this paper explored arable land use pattern which showed lower environmental risk and better sustainability. The research achievements were as follows:(1) The material flow analysis of high intensive agricultural land use systemThis dissertation established the material flow analysis method for agricultural land use system, to quantificationally analyze the material flow between agricultural land use system and the environment. The material input contained the fertilizer, pesticide, fodder, irrigation water, and oxygen. The material output contained the pollutant discharged by straw burning, the respiration of soil and livestock, the fertilizer surplus, the pesticide surplus and the pollutant from the livestock manure. The material flow storage contained the crop production and meat production. The result was as follows:affected by the change of planting structure, the direct material input (DMI) declined from 18669 million tons to 15733 million tons. On the contrary, the domestic processed output (DPO) increased from 57.70 to 73.66 million tons. Among the material input, the fodder, oxygen increased more than 2 times, the fertilizer and pesticide increased 55.28%、 152.77%, respectively. Among the material output, the pollutant discharging from staw burning, respiration, fertilizer surplus, pesticide surplus and livestock manure increased 9.73%、32.17%、 39.63%、147.06%、268.39%, respectively. The material input and output were much higher at suburban places on the edge of cities, which indicated that the urban area has become an ecological vulnerable place for agriculture. The agricultural economic output per unit of DMI and the agricultural economic output per unit of DPO increased by 24 times and 15.31 times, respectively, which showed that the agricultural economic benefit turned to rely less on resource consumption and pollution.(2) Evaluation of the composite environmental risk in the high intensive agricultural land use system and analysis of the influence factorsOn the basis of pollutant output, the environmental risk of high intensive agricultural system was classified into four categories:the greenhouse emission, the air pollutant emission, the eutrophication elements and the accumulated viruieni pollutant. We used the entropy weight method to calculate the composite environmental risk index, and used the principle component analysis method to analyze the influence factors of the environmental risk. The result was as follows:the greengas emission, the air pollutant emission, the eutrophication elements and the accumulated virulent pollutant increased 24.77%.8%.31.58%.256.25%, respectively. The composite environmental risk index in the suburban areas and the traditional agricultural couties was much higher than the other areas. In addition, affected by the industrial restructuring during the urbanization process, the composite environmental risk in Zhuzou City, Xiangtan City, Changsha City and Yueyang City increased lessly than the other areas. Moreover, the influence factors of environmental risk could be divided into two principle components:one is economic development and consumption need, the other one is government control and technology improvement, which showed a significant influence on the agricultural environmental risk.(3) Pre-warning of environmental risk in the future agricultural land use scenariosUsing the two principle components which affected the environmental risk as the uncertainty axis and taking 2030 as the objective time, this dissertation established the agricultural land use scenarios(ND, PD, MI and LR scenarios) under different economy and technology levels to analyze the food demand, arable land demand, material input, material output and environmental risk in the future. The results were as follows:the production of crop and meat will be 37.8,40.31, 39.48 and 32.42 million tons in ND, PD, MI, LR; the arable land demand will be 2.065.1.86.1.95. 1.78 million ha; the material input per ha will be 11.28,12.21,11.15.11.33 thousand tons/ha; the total pollutant output will be 113.17,180.23,95.31,64.52 millon tons.The composite environmental risk index shows a higher data in suburban areas. Though the intensive use of agricultural land showed advantages in sparing land, whereas it brought huge chanllenge to the environmental load capacity, as a result, the moderate intensive use of agricultural land is of great importance.(4) The regulating measures of the environmental risk at the basis of moderate intensive agricultural land useFrom the viewing angle of moderate intensive agricultural land use, this study put forward three regulating measures of environmental risk:First, control the material inputs and outputs. To satisfy the food need and production task of Dongting Lake basin, in 2030, the crop and meat production would be 32.95 and 6.53 million tons, respectively. On the basis of reduction of material input and output in the land use system, the controlling target were set:the nitrogen fertilizer, the phosphorus fertilizer, the potassium fertilizer, the pesticide input should be 0.14-0.15t/ha.0.10～0.11t/ha.0.20～0.21t/ha、0.012～0.016t/ha, respectively; The effective utilization rate of the nitrogen fertilizer, the phosphorus fertilizer, the potassium fertilizer, the crop straw, the pesticide and the livestock’s manure should be higher than 40%、25%、50%、75%、45%、50%.Second, optimize the spatial distribution of the arableland. After analyzing the spatial data of the land’s production potential, economical zone bit, and the ecological security, we found that the high quality arable land and the cultivated land reserves were located in the zonal area around Dongting Lake, whereas the inferior low quality arable land located in the west-northern Wuling mountainous area, the east-southern hilly area, and the densely populated big cities and their surrounding area. The area of arable land which has medium and high quality was larger than 19509 km2, which indicated that after land consolidation of the medium and high quality land, the total area of arable land in 2030 could satisfy the land need of agricultural production. In the future agricultural planning and land-use planning process, more focus should be put on the adjustment of arable land distribution, to move more agriculture to the high quality land. The arable land should be more concentrated and quit from the city development area appropriately, in order to release more space for urban expansion.Third, regulate the policy system of environmental protection. The policy regulation should emphasize more on the protection of agricultural land area, the scale operation of arable land, the adjustment on overall plan for land utilization, and the agricultural funds safeguard, etc. Through these diversificated measures, the environmental risk in agricultural land use system could be effectively controlled in the future.In general, mastering the possible change of environmental risks during the intensive agricultural land use process, and realize the moderate agricultural land use from making reasonable agricultural plan, improving production effiency, optimize the arable land distribution and policies, showed a significant importance in avoiding the possible environmental risk in advance.