To identify whether a degradation threshold exists that defines the boundary between the possibility of natural recovery and the need for artificial restoration of an ecosystem, and to use this knowledge to support the development of a suitable strategy for environmental restoration, assistant Prof. GAO Yang, Institute of Geographic Sciences and Natural Resources Research (IGSNRR), CAS and Prof. CAO Shixiong, Beijing Forestry University performed long-term monitoring of vegetation recovery in China’s Changting County since 1984.

Research results identified a degradation threshold at about 20% vegetation cover suggesting that for some sites, vegetation cover can serve as a simple proxy for more sophisticated approaches to identifying thresholds; restoration must start with the restoration of soil fertility and continue by facilitating vegetation development. They support the concept of ecological thresholds (specifically, for soil services in a warm and wet region), and provide a model to inform restoration strategies for other degraded ecosystems.

The “irreversible loss of soil services” described in this study, whether at national, regional, or local scales, will have a variety of thresholds, and it will be necessary to calibrate this index for different regions before it becomes a useful management tool. However, as the results show, it is possible to identify useful proxies for thresholds and use them to guide subsequent management of degrading sites.

The related research results have been published in Journal of Applied Ecology. (Gao Y, Zhong BL, Yue H, Wu B, Cao S. A degradation threshold for irreversible loss of soil productivity: a long-term case study in China. Journal of Applied Ecology, 2011, 48, 1145-1154.IF=4.970)

Figure 1. An example of the “irreversible loss of soil services” that has occurred in some plots in the study area. When vegetation cover decreased to less than 20%, heavy soil erosion occurred, leading to topsoil loss and declining soil fertility. As a result of erosion, the soil surface lost fine materials and the bare surface became enriched in sand and coarse materials. (Imaged by Dr. GAO Yang, IGSNRR Email: gaoyang@igsnrr.ac.cn)