In many ecosystems ungulates have coexisted with grasslands over long periods of time. However, high densities of grazing animals may change the floristic and structural characteristics of vegetation, reduce biodiversity, and increase soil erosion, potentially triggering abrupt and rapid changes in ecosystem condition. Alternate stable state theory provides a framework for understanding this type of dynamic. In the Sanjiangyuan atop the Qinghai-Tibetan plateau (QTP), grassland degradation has been accompanied by irruptions of native burrowing animals, which has accentuated the loss of ground cover. Severely degraded areas of alpine meadows are referred to as ‘Heitutan’. Here, using the framework of alternate stable state theory, we describe the proximate and ultimate drivers of the formation of Heitutan on the QTP, and we assess prospects for recovery, in relation to the degree of biophysical alteration, of these alpine meadows. Effective rehabilitation measures must address the underlying causes of degradation rather than their symptoms. Heitutan degradation is not uni-causal. Rather it reflects different mechanisms operating at different spatio-temporal scales across this vast region. Underlying causes include overly aggressive exploitation of the grasslands (e.g. overgrazing), amplification of grazing and erosion damage by small mammals when outbreaks occur, and/or climate change. Given marked variability in environmental conditions and stressors, restorative efforts must vary across the region. Restoration efforts are likely to yield greatest success if moderately and severely degraded areas are targeted as the first priority in management programmes, before these areas are transformed into extreme Heitutan.

The frigid swampy meadows of the Qinghai–Tibet Plateau in western China have suffered widespread degradation. The severe degradation of such meadows can lead to the formation of a landscape commonly known as heitutan. Much research has been undertaken to study its triggers, formation mechanism, grading of severity, and rehabilitation. These studies are comprehensively reviewed in this paper. In particular, it attempts to reconcile two divergent theories on heitutan formation by proposing a new model to elucidate the role of a given factor at each stage of degradation. In this model, climate desiccation is the most important in transforming healthy meadow to dry grassland, while rodent attack is the most important in worsening dry grassland to degraded meadow. Overgrazing is the most important factor during the early stages of degradation. Wind and water erosion is important during the final stage, when a large quantity of loose materials has been accumulated by rodent burrowing. Also covered in this paper is how to rehabilitate heitutan to productive use, including the effectiveness of various measures. Finally, this paper identifies the gap in our understanding of swampy meadow degradation and spells out a future research agenda. It is concluded that future research on heitutan will undergo a transformation from descriptive to quantitative. The expected research outcome will inform herders of the appropriate strategies that can be adopted to prevent heitutan formation. This proactive approach will minimize economic loss from swampy meadow degradation and reduce its adverse impact on the environment.