Environmental Risk Management For China's Intensive Agricultural Land Use

China has been experiencing rapid economic development,population explosion and ever decreasing arable land in recent decades.The large population has challenged China's agriculture sector.The immediate response to feed the population is to increase agricultural production by intensive agriculture with higher levels of input and output per land area.Intensive agriculture involves increased use of land inputs such as fertilizers,pesticides,mechanized agriculture,etc.Although the excessive use of chemical agricultural chemicals and the agricultural waste discharge has significantly increased crop produce,it has generated negative environmental consequences,such as soil and environmental quality reduction.In China,the land use intensity is higher,and chemical inputs are more excessive in intensive agriculture areas.In these areas,agricultural land use faces double challenges to secure food security and eco-environment safety.Thus,it is an arduous and urgent task to achieve sustainable agriculture and rural development by reducing or controlling environmental risk of agricultural land use.This research has created an environmental risk management framework for agricultural land use system based on the theories and methods of system science,man-land relationship,sustainable development,risk management,rural households' behavior choice etc.We have analyzed the intensive agricultural land use system from a system perspective.This study has chosen Taojiang as a case area to identify,assess,map and control environmental risk at regional scales.The main contents and results from the study are as follows.1.Assessing the effect of China's agricultural land use system on environmental impacts at a national scale.This research has identified major environmental risk sources in China's arable land use system based on a systematic analysis.We have assessed the nonpoint source(NPS)pollution from different arable land use practices.These land use practices involve the application of chemical fertilizers,pesticides and agricultural mulching,and the crop straw disposal.The results have provided comprehensive and baseline knowledge of NPS pollution from arable fanning system within China in 2014.The nitrogen(N)and phosphorus(P)emission loads to water were,respectively,1.44 Tg N and 0.06 Tg P.East and south China showed the highest load intensities of nutrient release to aquatic system.And,Acetochlor was the major source of pesticide loss to water,contributing 77.65%to the total loss.The environmental impacts of pesticide usage in east and south China was higher than other parts.For the agricultural plastic film mulching,19.75%of the plastic film application resided in arable soils,which contributed a lot to soil phthalate esters(PAEs)contamination.In China,14.11%of straw produce were burnt in situ,most occurring in May to July(post-winter-wheat harvest)in North China Plain and October to November(post-rice-harvest days)in Southeast China.All the above agricultural NPS pollution loadings were unevenly distributed across China.In addition,correlations of pollution loads on provincial scale were estimated.Rising labor cost in rural China might be a possible explanation for the general positive correlations of the pollution loads.It also indicated a co-occurred higher NPS pollution loads and a higher human exposure risk in populous regions.2.Environmental risk identification,assessment and mapping for regional agricultural land use system at regional scales.The Dongting Lake basin is one of the most important grain produce areas in China.We took Taojiang County in this area as the study case to explore how to identify,assess and map environmental risks of agricultural land use systems at regional scales.The results have showed that soil heavy metal pollution and eutrophication has been the major environmental risks in Taojiang.And pesticide application and film mulching,and crop straw in situ burning should also be paied more attention in environmental risk assessment.The environmental risk assessment shows that the risk level of N and P erosion loss,pesticide loss and application risk,crop in situ burning and soil heavy metal pollution were relatively high.But the environmental risk level of film mulching was relatively lower.The pollution loads from different sources were unevenly distributed.We have mapped the comprehensive environmental risk from two perspectives,the environmental impacts of the risk factors and vulnerability of risk acceptors.The mapping results indicated that positive spatial correlation was observed between the impacts of risk factors and the vulnerability of risk acceptors.This might lead to higher exposure level of the population and water environment,which reminded us to enhance environmental risk management in the key areas.3.Environmental risk control for agricultural land use system at regional scales.This research has built an environmental risk control framework for regional land use system.This framerok involves three parts,rural livelihood analysis and land use practice optimization,land transfer policy adjustment,soil heavy metal pollution zoing and field control measures.Our analysis is based on vast rural household data and experiment data.The results have showed that rural households'livelihood was in livelihood transition process.It was essential to understand the characteristics of livelihood trasitions for guiding farmers' land inputs to reduce the environmental risk of land use practices.In Taojiang,over half of the arable land was transferred to large scale farmers.Our results showed that the land transfer and large scale farming in Taojiang had led to pesticide and fertilizer use reduction,although which had resulted in crop produce decline.As the frequent land transfer had increased land area of large scale farming,it might reduce the environmental risk of land use practices in the intensive agriculture areas.Governments could control local environmental risk by guiding land transfer in the study area.In addition,soils serve as the most important sink for heavy metal contaminants in the terrestrial ecosystem.Heavy metal pollution is covert,persistent and irreversible.It is very difficult to remove from soils.This research did great efforts to manage soil heavy metal pollution by introducing soil-plant heavy metal synergistic risk for risk zoning and field management.