工业园区建设过程中生态环境变化及农地流失问题的研究

以某工业园区为例,通过对农田生态系统服务功能的分析,以及该区农地价值评估,指出农地城市流转对生态环境产生的影响,及农地流转带来的资源、环境和农地流失问题。

粮食充裕假象与农地流失

当前,所谓"中国粮食充裕"实质是个假象,但是有些人对此缺乏正确认识仍在大肆征购农用土地,使农地大量流失而严重威胁着粮食生产。为此,我国在工业化城市化运作中必须采用一系列政策措施,切实保护农用土地,以维持粮食的正常生产。

乡村振兴战略背景下农地流失现状与保护策略分析

随着乡村振兴战略的提出,越来越多的视线聚焦在农地流失与保护问题上。在我国城市化、工业化进程的加快、用地需求日益强烈的大背景下,农地征用的规模在不断扩大,失地农民人数逐年增加,并迅速扩大为一个社会群体。实践表明,“三农”问题的核心是农民问题,而解决好农民问题的关键就在于解决好农民的土地问题。否则,不仅会加剧城乡矛盾,影响我国的城市化进程,甚至会危及社会主义和谐社会建设。因此,本文在乡村振新的战略背景下,认真研究目前农地流失的现状及其原因,并结合国内外的研究现状,希望能找出有效的治理措施,提出合理的建议。

农地新政与国民经济运行格局的重构

农地流失是一个普遍的事实,但失去土地的农民却未能分享到发展的成果。关键在于,模糊的农地制度安排提供了农地流失的制度供给,政府主导经济增长的体制机制则提供了农地流失的制度需求。中国经济快速增长的"奇迹"在相当程度上是地方政府谋求经济增长及其"土地财政"而以农地资源的广泛流失与浪费为代价的。十七届三中全会通过的《决定》的精神实质与政策指向,旨在通过以土地为核心的制度变革及其政策硬约束,来促进经济增长方式的转变与国民经济运行格局的重构。

分税制、财政压力与政府“土地财政”偏好

分税制导致了地方财政收入和支出间的巨大缺口;而地方财政压力所引发的工业化与城市化冲动,形成了普遍的"占地竞赛"。获取"土地财政"成为政府的普遍"偏好"。分税制进而地方财政压力导致了对土地的掠夺;有必要对政府的"土地财政"进行测算;以阐明农地为什么会成为掠夺的对象。改善分税制的制度设计,强化地方政府预算外和预算资金收入的约束和规制,特别是变革农地产权制度,推进农民土地权利的法律保障以及对农民行使产权行为能力的保护,是改变"分税制"—财政缺口—土地财政—农地流失运行逻辑的关键。

产权安排、征地制度与农民权益保护

由于我国农地产权的形成是国家强制安排的结果,这种赋权方式严重弱化了农户拥有的产权强度,而集体经济组织作为农地的法定所有权人却没能得到法律清晰的界定。产权强度的弱化和产权主体的模糊为政府在征地中侵占农民权利提供了寻租空间。更为严重的是,我国现有的征地制度安排存在诸多问题,没有给农民权益以切实的保护,因此明晰农地产权主体,正确界定公共利益,完善社会保障等成为征地制度改革的选择。

Characteristics of Nitrogen and Phosphorus Losses in Different Crop Rotation Systems in the North of Erhai Lake Basin

[Objective] Nitrogen and phosphorus losses of surface runoff in various crop rotation systems in the north of Erhai Lake basin were studied with the objective to provide references for risk evaluation of environmental pollution and formulating countermeasures to control the nonpoint source pollution from agriculture.[Method] Water samples collected in four typical crop rotation systems distributed in seven towns（townships） in the north of Erhai Lake basin were investigated,as well as the fertilizer input,to explore the dynamic change of nitrogen and phosphorus content in surface water of farmland and ditch water,and the correlation between fertilizer input and the concentrations of nitrogen and phosphorus in the surface water of farmland and in the ditch water.[Result] The results showed that nitrogen loss in surface water of farmland in different crop rotation systems differed greatly,and the risk of nitrogen loss was 38% lower in broad bean-rice crop rotation than that in garlic-rice crop rotation.The water soluble nitrogen was the primary form of nitrogen loss.The content of water soluble nitrogen was significantly higher in garlic-rice crop rotation than that in the other rotation systems,and the concentrations of nitrogen in the surface water of farmland in different crop rotation systems followed the sequence below：garlic-rice crop rotationryegrass-rice crop rotationbroad bean-rice crop rotationrape-rice crop rotation.The loss of phosphorus in the surface water of farmland was relatively low and phosphorus combined with silt was the primary form for phosphorus loss.There was no significant difference of the loss of various forms of phosphorus in different crop rotation systems.The contents of total nitrogen and total phosphorus in the surface water of farmland were higher than that in ditch water,with increasing rates of total nitrogen and total phosphorus in ditch water of 72% and 82%,respectively.Topdressing was the critical reason for the high concentrations of nitrogen and phosphorus in the surface water,which also caused the increasing load to the ditch water.[Conclusion] Both the nitrogen and phosphorus loss were the highest in garlic-rice crop rotation.Reasonable crop rotation systems should be established based on both the environmental and economic benefits.This study provided references for controlling the nonpoint source pollution of farmland and improving the water quality of Erhai Lake.

An Integrated Quantitative Method to Simultaneously Monitor Soil Erosion and Non-Point Source Pollution in an Intensive Agricultural Area

In China, some areas with intensive agricultural use are facing serious environmental problems caused by non-point source pollution(NPSP) as a consequence of soil erosion(SE). Until now, simultaneous monitoring of NPSP and SE is difficult due to the intertwined effects of crop type, topography and management in these areas. In this study, we developed a new integrated method to simultaneously monitor SE and NPSP in an intensive agricultural area(about 6 000 km2) of Nanjing in eastern China, based on meteorological data,a geographic information system database and soil and water samples, and identified the main factors contributing to NPSP and SE by calculating the NPSP and SE loads in different sub-areas. The levels of soil total nitrogen(TN), total phosphorus(TP), available nitrogen(AN) and available phosphorus(AP) could be used to assess and predict the extent of NPSP and SE status in the study area.The most SE and NPSP loads occurred between April to August. The most seriously affected area in terms of SE and NPSP was the Jiangning District, implying that the effective management of SE and NPSP in this area should be considered as a priority. The sub-regions with higher vegetation coverage contributed to less SE and NPSP, confirming the conclusions of previous studies, namely that vegetation is an effective factor controlling SE and NPSP. Our quantitative method has both high precision and reliability for the simultaneous monitoring of SE and NPSP occurring in intensive agricultural areas.