Emergy evaluation of cropping, poultry rearing, and fish raising systems in the drawdown zone of Three Gorges Reservoir of China

The agricultural production in the drawdown zone of Three Gorges Reservoir of China has been gradually attracting people's attention in recent years. As influenced by both excessive farming and artificially regulated water level fluctuation, the environmental sustainability of the agricultural system in the drawdown zone is being concerned widely with its production mode and increasing use of agricultural chemicals. Emergy method was used in this study to evaluate the environmental performance of the three agricultural production systems, i.e., cropping, poultry rearing, and fish raising system in the drawdown zone of Three Gorges Reservoir of China. Additionally, to attain a comprehensive understanding of the driving force of respective system's production, some economic indicators are selected to learn the economical efficiency of the three systems referred. The results indicate that the purchased nonrenewable resource accounts for a major portion in cropping production, whereas the renewable resource input constitutes the main part in poultry rearing and fish raising systems. The emergy yield ratio (EYR), environmental loading ratio (ELR), emergy sustainability index (ESI), and economic output/input ratio indicate that the cropping system is less well performed than the poultry rearing and fish raising systems on environmental sustainability, albeit with a relatively higher economic output and net profit. To achieve an environmental sustainable agricultural production, green and clean energy should be advocated to use in the cropping system. At the same time, the government should provide some policy supports to develop an intensive poultry rearing and fish raising productions for raising local farmers' income. Besides, it should be noted that, a controversy about whether the drawdown zone land should be used or not is gradually becoming a social dilemma in Three Gorges Reservoir area. In the long run, the cooperation between the government and local farmers is crucial for alleviating this contradiction, whereby the drawdown zone area's agricultural production could achieve a sustainable development with a light environmental impact.