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城市近郊耕地流失的贝叶斯机制解析及风险评估

Mechanism analysis and risk assessment of cultivated land loss based on Bayesian network in the urban periphery

  • 摘要: 解析城市近郊地区耕地流失时空特征并揭示空间要素驱动机制,对维护国家粮食安全、促进耕地保护与科学管理具有重要意义。该研究以浙江省宁波市鄞州区为例,基于历年土地利用变更调查数据和GIS空间分析解析城市近郊耕地流失的时空变化特征,在构建耕地流失贝叶斯网络模型的基础上,通过节点的重要性对耕地流失的关键驱动因子进行系统甄别,并利用诊断性分析和概率推理创新性地对现存耕地流失风险进行预判。研究结果表明:2009—2021年间研究区耕地流失较为剧烈,耕地流向以建设用地和林地为主,耕地流失模式反映了城市化扩张、生态经济转型和特色产业发展对耕地利用和结构性转变的驱动作用。农业结构调整惯性力因子对耕地流失的驱动作用显著,建设占用惯性力次之;而耕地功能重要性对耕地流失的影响效果相对较低。政策规划因子对耕地流失概率作用较大,特别是耕地保护补贴对耕地流失起到了较强的作用效果。鄞州区耕地流失风险呈现不同程度的空间分异特征,兼具优越生态本底条件与显著优势区位的区域面临耕地流失的多重胁迫风险。该研究认为,应当针对不同风险等级耕地空间实施差异化策略,多措并举加强政府、市场、农业经营主体在耕地保护与利用中的互动性连结,实现耕地资源高效治理。

     

    Abstract: Spatial and temporal features of the cultivated land loss in the urban periphery are of major significance for food security. The influencing factors can also dominate the resource allocation of the cultivated land. This study aims to analyze the spatiotemporal features of the cultivated land loss using the land use change survey data and GIS spatial analysis. A case study was taken of the Yinzhou District in Ningbo City, Zhejiang Province, China. Then, a Bayesian network model was constructed to identify the key influencing factors on the cultivated land loss using the node importance. The risk of the cultivated loss was also predicted using diagnostic analysis and probabilistic inference. The results indicate that: 1) A total of 11 153 original cultivated land patches were lost from 2009 to 2021. And 50 345 new patches emerged to cover a cumulative area of 8,599.54 hectares after transformation and fragmentation, which accounted for 40.6% of the total cultivated land area in 2009. Only 59.4% of the cultivated land remained under stable utilization. The primary pathways of the cultivated land loss were converted to construct the cultivated and forest land. Specifically, approximately 38.7% of the lost cultivated land was converted into construction land. While about 26.2% was transformed into forest land. Such a transformation pattern represented the urban expansion, ecological-economic reconstruction, and the characteristic industries of the cultivated land use. 2) The driving force of the agricultural structure had a significant effect on the probability of the loss of cultivated land, followed by the driving force of the construction occupation. There was a relatively low importance of the cultivated land functions on the cultivated land loss. While decision-making factors had a significant impact on the probability of the cultivated land. Especially, the subsidies for the cultivated land also played a relatively strong role in the loss of cultivated land. There were the polarized patterns of the agricultural protection subsidy factor. The agricultural structure was significantly impacted by farmland protection subsidies, either very large or extremely low. “Threshold Effect” in behavioral economics was attributed to the polarization of the agricultural protection subsidies. Behavioral change only occurred when the subsidy level surpassed the “significance threshold” in farmers’ minds. Besides, there was the relatively small influence of the neighborhood and natural factors on the probability of cultivated land loss. 3) The risk of the cultivated land exhibited spatial differentiation. Urbanization frontier regions (like Xiaying, Panhuo, and Meixu) were geographically associated with the high-risk locations. The sub-high-risk locations were observed in the intersection of Shounan, Yunlong, and Dongqian Lake, as well as the shoreline of Zhanqi and Xianxiang. The majority of the medium-risk locations were found in the transitional spatial units, including Wuxiang, Tangxi, and Hengxi. The primary locations of the low-risk areas were found in the towns and villages with flat terrain and an endowment of cultivated land. Overall, the high risks were observed in both favorable ecological and advantageous geographic locations, due to the multiple overlapping pressures. In conclusion, some strategies must be employed according to the varying risk levels of the cultivated land. While the various measures were concurrently implemented to enhance the interactions among the management, the market, and agricultural entities in the cultivated land use. Thereby, the findings can also provide a strong reference for the decision-making on the cultivated land resources.

     

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