Natural restoration is mainly accomplished by allowing natural reforestation to occur, combined with prohibiting agriculture and grazing to reduce human disturbance of the environment. Taking advantage of the succession that occurs in natural ecosystems is a common ecological restoration measure that can restore ecosystems and keep them in balance. However, conservation and restoration biologists have increasingly recognized that ecological communities are likely to exhibit threshold changes in structure that may prevent succession from occurring. Because long-term monitoring data are generally lacking, little is known about the consequences of such ecological thresholds for the processes of ecosystem degradation and recovery. 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, we have performed long-term monitoring of vegetation recovery in China's Changting County since 1986. We found a severe problem in this area, which we refer to as the "irreversible loss of soil services": when vegetation cover decreases below an ecological degradation threshold, leading to sustained degeneration of the vegetation community, erosion of the surface soil and declining soil fertility occur. These changes represent a severe and long-term disturbance of the vegetation, the soil, and the landscape. We identified a degradation threshold at about 20% vegetation cover, which suggests that for some sites with a vegetation cover of between 20 and 30%, vegetation cover can serve as a simple proxy for more sophisticated approaches to identifying thresholds; when vegetation cover declines to this level, restoration must start with the restoration of soil fertility and continue by facilitating vegetation development. Our results support the concept of ecological thresholds (specifically, for soil services in a warm and wet region of China) and provide a model to inform restoration strategies for other degraded ecosystems. Ecosystem restoration sometimes fails because ecological interactions are more complex or human intervention is more difficult than anticipated; factors other than human disturbance, such as climate variability (e.g., a drought shortly after planting), can result in failure of a strategy that would succeed under better conditions. Some degraded ecosystems can be sustained only through ongoing management, but many conservation efforts preclude such interventions. Although ecologists can recognize many of the species changes that are likely to precipitate threshold changes in community composition, biotic interactions can be unexpected, and because responses often depend strongly on local conditions, they cannot be broadly generalized. For example, complex ecosystems with multiple interacting species may have multiple thresholds based on different components of the ecosystem. Desertification is another example and has been shown to result from strong biogeomorphic feedbacks that operate across several spatial scales. When overgrazing of arid grasslands reduces vegetation cover, water infiltration decreases, further limiting plant growth and leading to persistent desertification. Such spatial discontinuities, called ecotones, can be detected using multivariate data ordered in one dimension through comparisons of measures of dissimilarity computed between the systems on either side of the discontinuity. The "irreversible loss of soil services" described in our 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 our results show, it is possible to identify useful proxies for such thresholds and use them to guide subsequent management of degrading sites.