Restoration of degraded ecosystems and development of water-harvesting ecological agriculture in the semi-arid Loess Plateau of China
半干旱黄土高原退化生态系统的修复与生态农业发展

The natural regional vegetation and soil quality in the semi arid Loess Plateau of China have been degraded extremely due to over grazing and frequent reclamation of natural grassland. Functions of the ecosystems and regional sustainable development were seriously threatened. The analysis of the current ecological environmental situation suggests that transformation of natural vegetation to farmlands in the process of frequent reclamation of natural grassland results in water loss, soil erosion and land degradation. Repeated reclamation of wasteland due to the great pressure of food demand resulted from population growth is the key driving force to the degradation of these ecosystems. To restore natural vegetation and soil quality, we have to find a way to meet the requirement of food for the local farmers in a small portion of the land to reduce the pressure of food production for the rest of the land of a region. In semi arid areas, many studies have shown that the key step for increasing grain yield per unit area is to improve field environmental conditions, including soil moisture supply, topsoil temperature and soil nutrient level. This can be accomplished through the combination of water harvesting technology with plastic film mulching and fertilizer application, which can generally increase the unit grain yield twice or more. Based on these technologies, we propose an approach of water harvesting ecological agriculture (WHEA) and associated landscape configuration in the paper. Unit yield of cash and grain crops can be increased greatly through limited irrigation, and the irrigated cropland can be interspersed with improved pastures and restored natural vegetation in a continuous landscape (a typical hill) in WHEA. Further research and dissemination of WHEA can help supply local farmers with sufficient food and higher income. Various types of grasslands will replace cropland and cover a large proportion of the landscape; animal feeding will be mainly dependent upon pen feeding in order to decrease grazing pressure. These strategies closely follow the ecological patterns of natural vegetation and landscape, as well as the planning pattern of regional industrial arrangement. The coexistence of multiple ecological and economic systems in a landscape helps to improve both biodiversity and industrial diversity, and enhance the flexibility and stability of these systems. Therefore, WHEA, an innovative approach for regional development, can lead to significantly improvement in both the restoration of degraded ecosystems and regional sustainable development simultaneously in the semi arid Loess Plateau.