Emergy–Based Sustainable Development Research Of Agro–Ecosystem In The Loess Hilly Area Of South Ningxia

Agriculture provides the basic human survival guarantee and it is the foundation of the national economic development, so the sustainable development of agriculture is an important part to realize the sustainable development of the whole society. In recent decades, with the growing of demand, agricultural development is faced with the threat and risks of ecological environment problems, such as shortage of resources, land degradation, soil pollution. These problems seriously influenced the production function and the ability of sustainable development for agricultural system. The loess hilly-gully area of south Ningxia is located in the west of the loess plateau, and it is the typical ecological fragile zone of farming-pastoral part in north China. At present, this region is facing the threat of ecological imbalance, natural disasters and serious soil erosion as a result of successive cultivation and unreasonable use of land. Crop cultivation is the single and main production mode for many years in this area. Because the extensive cultivation, farmers live in poverty. These problems have already severely restricted the harmony development in regional economy, society and environment. After liberation, this region was included in the scope of Poverty Alleviation Program of “Three West”. In order to improve the lagging condition, the government has increased investment in the construction of ecological restoration and agricultural production structure adjustment. And, Chinese Academy of Sciences has achieved remarkable results through establishing experimental area in comprehensive treatment of agricultural environment for more than 30 yeas. So, we selected Yuanzhou County, a typical ecological fragile area of the Loess Hills zone, as the study area to analyze the development tendency of agricultural system in recent decades based on emergy analysis. Through quantitative research of its sustainable development from various perspectives, this thesis attempted to provide strong basis for rational utilization of agricultural resources and regional scientific decision-making of agricultural development. According to this objective the core contents of this paper include:Based on the theory of sustainable development, ecological economics, resource science and basic principle of artificial- natural compound system, using the emergy analysis, this paper analyzed the energy conversion process of agricultural ecological system in Yuanzhou County for 30 years, and revealed the dynamic changes of input–output framework of emergy and the relationship between human and environment in agricultural production, and evaluated its sustainable development capacity through the effective indicators; Using intuitive expression of phase diagram, revealed the relationship between agricultural production process and natural environment, as well as economic system, compared the resource allocation and development tendency with the different modes of resource utilization; Using the Ecological Footprint method combined emergy analysis, quantified and evaluated the sustainable use extents of cropland resources; Using the green GDP accounting method combined emergy analysis, evaluated the cost of resources and environment in the process of agricultural GDP growth. The main results obtained in this study were as follows:(1) From the perspective of present emergy input structure, the agricultural system of Yuanzhou County had a strong reliance on the natural environment. But because of the low level of technology, the efficiency of natural resources use was poor, so the agricultural system belonged to economic development model of serious resource wasting. The results showed that its agricultural production is still in the stage of traditional agriculture characterized by labor-intensive.(2) From the perspective of present emergy output structure, the leading industries of agriculture in Yuanzhou were planting and animal husbandry, and the proportions of forestry and fisheries were very small. Especially the planting occupied obvious advantage proportion(73.2%). The planting production includes wheat, corn, potatoes and oil plants. Among these, the output of oil seeds occupied first place(78.5%), and corn and wheat were in second. The emergy output ratio was 2.81 in 2012. This means that the whole function of region’s agricultural production system ran well, and emergetic returns was high. But through the indicators of environment load ratio and emergy sustainability, we found that the agricultural environment was under tremendous pressure in Yuanzhou County, and ecological degradation has seriously hindered the sustainable development of agriculture. The agricultural system was in a state of unsustainable development.(3) From 1983 to 2012, the efficiency of the agricultural system of Yuanzhou County had increased remarkably due to the improvement of structure for input and output. In terms of the structure of emergy input, the agricultural production of study area was no longer simply relying on environmental resources to maintain, and the dependence on feedback from the system economy was growing. In terms of the structure of emergy output, main body of agriculture in Yuanzhou was planting and animal husbandry. The output contribution rate of forestry and fishery were very small, and there was no increased trend from 1983 to 2012. The emergy output structure of planting has changed remarkably. This change was another important reason that efficiency of agricultural system has greatly increased in studied area. To be corresponding to this, the trend of emergy output ratio showed that the output capacity of agricultural system has enhanced, and the ecological balance has converted from emergetic deficits into emergetic surplus in 2001. But the ability of sustainable development was weak, and the system was in a state of unsustainable development during 30 years. Through the sustainable analysis of cropland utilization in Yuanzhou County, the results showed that the cropland use was in the ecological deficit, and it was unsustainable since 80’s. This also meant that the ability of cropland to support development of society and economy was weak with notable contradictions between human and land. But the cropland use at present was developing in the direction of intensive management. This would be helpful for the economical use of land and easing of pressures on cropland in Yuanzhou County. At the same time, the results of agricultural green GDP accounting further indicated that resources and environment cost ratio has increased. That is, the positive effects of national economy growth(wealth) were reducing, while the negative effects that against the sustainable development were increasing.(4) We evaluated the sustainable development of agricultural eco-system the condition using different method. The results show that the development of agricultural ecosystem in study area was unsustainable. And unsustainable situation tends to weaken with the improvement of ecological condition in the study area. Population growth, irrational use of agricultural resources and poor natural climate conditions were major causes that led to unsustainability. So the sustainability would be improved if take some necessary measures such as increasing investment of agricultural technology, adjusting agricultural structure and strictly controlling of population and so on.