Feedback & Simulation Study On Ecosystem Management For Rural Pig Production Area And Its Application

The pig production has been transferred from outskirts of big cities to the agricultural regions in Midwest China since 2002. The pig production belt is formed with the Middle & Lower Area of Yangzi River as its center, and spreading towards Southern and Northern regions. Due to the scale efficiency, favorable breeding conditions in South China, and the encouragement of government, the Specialized Pig Breeding Households are developing rapidly. The professional pig farming family and the medium-and small-scale specialized pig breeding household are the principal part of pig production in China rural areas now, and even a long periods aftertime.The scale pig production has brought more and faster comparative benefits to farmers than planting in agricultural regions. However, the severe pollution of cumulated breeding wastes are accompanied with the rapidly growing pig numbers, the great environmental damage which brings to the agricultural ecosystems are not allowed to be left alone again. Therefore, the government has invested largely to build anaerobic digesters for farmers, and encouraged them to use anaerobic digestion technology to dispose of the pig production excreta in recent years, which have greatly solved the pollution from excreta discharge.Unfortunately, the second pollution caused by the residual product of anaerobic digestion is flowing automatically. Investigation shows that in most farming areas, especially in many remote villages, the anaerobic digestion liquid, biogas is let directly into atmosphere due to the lack of consumers and funds. The main components of the biogas released are CH4 and CO2 that are two kinds of greenhouse gas. Additionally, abundance of organic wastes in the effluent after digestion flow freely into backward water area thus polluting water areas on the way, potable water, agricultural ecology, and living environment severely.The actuality always is one pig breeding Household pollutes the whole agricultural system in farming areas.The dissertation selects Jiangxi province, which is a main paddy production region in the Middle & Lower Area of Yangzi River, as its research spot, and Taihua pig production farm, which is a pig fanning family, owned by Pen Yuquan, located in Paishang town, Pingxiang Region, Jiangxi Province is selected as a case study. The farmers' income, the resource utilization of farming residues, and paddy planting in the case are considered as a part of the scale pig production environmental management. With the SD feedback dynamic complexity analysis theory and approaches, a series of management strategies for eliminating second pollution in rural areas of Jiangxi Province are given and the engineering for implementing the strategies are also designed, which will ensure the aim of economy development and the environment in farming areas to be protected.The main research conclusion was summarized as follows:1. The evaluation indicators and methods to assess the environmental impact of farms are extended to the regional level environmental impact evaluation. Four environmental indicators, such as ecological footprint, loading of pig production excreta nitrogen per hectare arable land, loading of pig production excreta phosphorus per hectare arable land, and global wanning potential(GWP) expressed as kg CO2-eq/kg FPCM the component are adopted and calculated by component approach, the trail measurement and the discharge coefficient method, and the method advised by the IPCC Guidelines respectively, to assess the environmental impact of pig production in Jiangxi Province in year 2005. The assessing result shows that scale of pig production within Jiangxi province is still within its biocapacity; the pollution caused by pig production in rural areas is due to lack of piggery residues resource utilization as to leave the excreta cumulated in farming areas.2. Based on graph theory and system dynamics causal loop diagram theory, a new systemic analysis approach named vertex weighted causal loop diagram model approach to feedback dynamic complex system is presented is the dissertation. And the approach is applied to the analysis of growing limitation of Taihua scale pig production ecosystem.The stock flow diagram of complex systems always involves large numbers of variables, some relationship between them are ambiguity, some are depending on experimental dates, so it is difficult or even unable to put their relationships into mathematics equations some times, even more, the reliability of the equations are incapable to be tested. Therefore, a midst model between causal loop diagram model and stock flow diagram model of system dynamics was constructed in this dissertation, which was named the vertex weighted causal loop diagram model. The vertex weighted causal loop diagram approach is a qualitative and quantitative combined analysis approach, it starts from the value of the key variable of the system at a given time, and with this initial value, by equations of the correlated arcs or tested results of the vertexes, calculate the value of every vertex in the given time. After the value of every vertex is put into the casual diagram, the corresponding vertex weighted causal loop diagram of the studied system in the given time is generated; then by compare the dynamic variety of values of vertexes in different times, analyze the law of feedback effect of each positive and negative feedback loops of the system, to identify key leverage points and to design intervention strategies.The approach is applied to analyze the primary limits to the growth of Taihua scale pig production ecosystem, and five management strategies are put forward after that.3. A SD model of Taihua scale pig production ecosystem is constructed and three dominant archetypes for three corresponding main contradiction problems are generated respectively. The efficiency of strategies put forward after vertex weighted causal diagram analysis are simulated with the corresponding dominant archetypes.(1) In accordance with system qualitative analysis by the vertex weighted causal Loop diagram model approach, and based on the management strategies we have designed for the pig farming ecosystem, we divided the system into six subsystems; which are intensive pig farming subsystem, farmers' total income from the system subsystem, anaerobic digester effluent subsystem, paddy planting subsystem, vegetable planting subsystem, and biogas subsystem. For each subsystem, there is a corresponding in-tree; the total in-trees construct the rate variable fundamental in-tree model of Taihua scale pig production ecosystem.The in-tree model is composed of ten rate variables fundamental in -trees. The root of a rate variable fundamental in-tree is a rate variable, the level variables or other rate variables, external variables, constants (parameters) which control the root only through auxiliary variables is called the leaves of the in-tree.(2) All of the feedback loops of Taihua scale pig production ecosystem are obtained by calculating its diagonal-1 branch-vector determinant corresponding strongly simplified rate variable fundamental in-tree model. Choosing feedback loops which have direct relations to the problem, three dominant archetypes corresponding to the three system problems are constructed respectively. Then simulate the system behavior variation caused by the implementation of management strategies with the corresponding dominant archetype, to demonstrate, amend and confirm the strategies.4. The strategies engineering is designed and implemented in Taihua pig fanning areas, the economic and ecological benefit is distinct.The anaerobic digester effluent and irrigating water diffluent engineering is constructed in Taihua pig farming area in the April of 2006, and the problem of the reduction of paddy output is settled with the engineering; the cropland vegetable planting in winter fallow engineering started from the winter of 2005, and the vegetables are through the green vegetable test, the planting areas is broadened year after year; the recycle biogas utilization engineering is on building now. Favorable economic and environmental benefits are gained by the strategies implementing in Taihua pig farming area.5. By systemic analysis of the limits to growth of the medium-and small-scale specialized pig breeding household, a management policy popularization system network based on the farmers' professional cooperative organization is constructed.The mode of pig production healthy, breeding residues resource utilization, green vegetable planting, farmers' income growth, contamination elimination is circulating normally with the implementation of management strategies in Taihua pig farming area, which demonstrates that it is a effectual approach to settle the problem in the scale livestock production ecosystem by combining the SD feedback & simulation theory with other theories.