农业集聚对农业面源污染的影响——基于中国地级市面板数据门槛效应分析

农业集聚的环境效应相比其他产业更为复杂,然而学术界对此探讨较少。在理论分析的基础上,利用2007—2015年中国337个地级市面板数据,核算农业集聚水平与农业面源污染排放量,并采用空间分析技术、计量模型,实证探究农业集聚与农业面源污染的时空特征及农业集聚对农业面源污染的门槛效应。结果显示：① 农业集聚与COD、TN、TP三种农业面源污染在时序变化、空间布局、空间关联以及空间趋势变化上特征相异。② 农业集聚对COD、TN、TP农业面源污染皆呈现正相关的单门槛效应。低于门槛值阶段,农业集聚水平的提高显著加剧了农业污染,集聚水平跨过门槛值后,污染加剧形势有所缓和。③ 农业集聚与农业面源污染之间经历的两个阶段,取决于规模效应、结构效应、技术效应、社会效应、累积效应分别对农业面源污染排放的加剧与制约作用。随着农业集聚水平提高,各效应增污作用明显,导致污染水平显著提高,进入高于门槛值的阶段,各效应对污染排放的抑制能力提升,削弱了部分负环境外部效应。④ 农业经济水平、农业生产条件在一定程度上加剧了COD、TN、TP污染;畜牧业结构、环境规制对COD、TP污染存在显著的正相关关系;生产者素质的提高可以影响农户生产行为并改善农业环境。⑤ 农业集聚对COD污染的降污效应较弱,农业COD污染较为严重且主要来源于畜牧业养殖,畜牧业污染防治亟待加强。

Impact of agricultural agglomeration on agricultural non-point source pollution: Evidences from the threshold effect based on the panel data of prefecture-level cities in China

The environmental effect of agricultural agglomeration is more complicated than that of other industries, but there is a deficiency of the research on it. This study calculated the level of agricultural agglomeration and the emissions of agricultural non-point pollutants in Chinese prefecture-level cities by using the panel data of these cities on the basis of the theoretical analysis. Then we investigated the spatial and temporal characteristics of agricultural agglomeration and agricultural non-point source pollution and the threshold effect of agricultural agglomeration level on agricultural non-point source pollution based on GIS spatial analysis and econometric model. The main conclusions can be drawn as follows: (1) Agricultural agglomeration and agricultural non-point source pollution of COD, TN and TP show different characteristics in temporal variation, spatial distribution, spatial correlation and spatial trends. (2) Agricultural agglomeration has single threshold effect on COD, TN and TP pollution, and positive correlation with them. When the level of agricultural agglomeration is below the threshold value, it contributes to agricultural pollution significantly, and as the level of agglomeration becomes higher than the threshold value, the situation of rapid pollution will be mitigated. (3) The change from agricultural agglomeration to emissions of three agricultural non-point source pollutants develops in two stages. This change depends on the intensification and restriction of the scale effect, structure effect, technical effect, social effect and cumulative effect on the emissions of agricultural non-point source pollution produced by agricultural agglomeration and it is reflected in the concrete agricultural production behavior. With the increase of agricultural agglomeration, the effect of each effect is obvious and the level of pollution increases significantly, however, the inhibition ability of pollution emission is improved and the external effect of negative environment is weakened at the stage of crossing the threshold. (4) The agricultural economic level and agricultural production conditions aggravate the COD, TN and TP agricultural non-point source pollution to some extent; the structure of animal husbandry industry and environmental regulation have a positive correlation with COD and TP agricultural non-point source pollution; the improvement of producer quality can affect farmers' production behavior and improve the agricultural environment. (5) The effect of agricultural agglomeration on pollution reduction of COD agricultural non-point source pollution is weak and COD agricultural non-point source pollution is more serious and mainly from animal husbandry.