中国耕地非农化趋势及其对碳收支影响的模拟

Simulation of cultivated land conversion trend and its effect on carbon budget in China

伴随快速工业化、城镇化进程,中国耕地非农化不断加快,由此带来碳排放迅速增加、生态环境和温室效应不断恶化。鉴于此,该文将耕地非农化与碳收支纳入统一框架,运用系统动力学方法模拟1996-2020年间耕地非农化带来的碳收支盈亏量。结果表明:1)整体分析判断,中国耕地非农化处于递增趋势且空间分布主要集中在东部,并呈现耕地规模递减、建设用地递增状态。2)模拟结果显示,1996-2020年全国耕地由1.293×108hm2减少到1.204×108hm2,建设用地从2.407×107 hm2增加到3.073×107 hm2,并且耕地非农化碳汇量由7.90×108t减少到7.48×108 t,碳源量从9.34×109t增加到1.17×1010 t。3)区域比较发现,全国耕地非农化碳收支表现为碳源且总体上呈递增趋势,并且2020年东部地区碳支出量最大为5.029×109 t,西部次之为2.261×109 t,中部略小于西部为2.216×109 t,东北地区最小为1.084×109 t。

Along with the rapid industrialization and urbanization, China is undergoing increasingly aggravated cultivated land conversion. Consequently, it causes great damage to environment and the worsening of the greenhouse effect. Therefore, this paper puts the cultivated land conversion and carbon budget into a unified framework, and uses the system dynamics method to simulate and measure the carbon budget change caused by the farmland conversion from 1996 to 2020. Using the system dynamics software Vensim, the carbon budget system model based on cultivated land conversion is built, which emphasizes the population subsystem, economic subsystem, cultivated land subsystem and construction land subsystem. Then the dynamic behavior of each system is simulated and the change law is revealed. Firstly, through simulating and comparing the data of the cultivated land and construction land from 1996 to 2020, it is found that the cultivated land conversion is concentrated in the eastern region, and the area of China＇s cultivated land is decreasing while the construction land is increasing. The simulation results indicate that the area of cultivated land has reduced from 1.293×10^8 hm^2 in 1996 to 1.204×10^8 hm^2 in 2020, and the construction land has increased from 2.407×10^7 to 3.073×10^7 hm^2. Secondly, in the process of simulating the national carbon budget, the paper mainly selects the 4 variables which are construction land green area, ecological restoration, cultivated land and construction land. And their carbon sink/source correlation coefficients are obtained from previous research. The carbon budget measurement shows that from 1996 to 2020, the carbon sink based on national cultivated land conversion reduces from 7.90×10^8 to 7.48×10^8 t, the carbon source increases from 9.34×10^9 to 1.17×10^10 t, and the national carbon budget of the cultivated land conversion generally presents that the carbon expenditure increases from 8.55×10^9 to 1.10×10^10 t. Thirdly, the paper divides China into 4 regions（northeast, east, center and west） and makes regional comparison. The selection and estimation of parameters are similar to the whole country. The regional simulation results show that the carbon expenditure in the east is 3.569×10^9 t, in the west is 2.065×10^9 t, in the central is 1.991×10^9 t, and in the northeast is 8.99×10^8 t in 1996; and in the year 2020, the carbon expenditure in the east is 5.029×10^9 t, in the west is 2.261×10^9 t, and in the central is 2.216×10^9 t, and in the northeast is 1.084×10^9 t. And the capacity of carbon sink will be decreasing in 4 regions, the carbon source will be increasing significantly in future, and the carbon budget will present carbon expenditure which is predicted to increase but the increase is not huge. By comparison, the carbon source and carbon budget in east will increase mostly. The carbon sink, carbon source and carbon budget will be stable in northeast. So, the imbalance status of carbon budget in China is mainly caused by the eastern region.