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[1] Forest vegetation can interact with its surrounding environment in ways that enhance conditions favorable for its own existence. Removal of forest vegetation has been shown to alter these conditions in a number of ways, thereby inhibiting the reestablishment of the same community of woody plants. The effect of vegetation on an environmental variable along with vegetation susceptibility to the associated environmental conditions may imply a positive feedback: Changes in the internal conditions controlling this variable such as deforestation could inhibit the reestablishment of woody vegetation cover that in turn would act to further degrade the conditions necessary for forest regeneration. Understanding these feedbacks is important because in some cases where these feedbacks are present, deforestation can lead to irreversible state shifts where the forest vegetation cannot recover. In this review, we examine the different cases in which deforestation can lead to a loss of conditions necessary to sustain forest vegetation. We examine the spatial scale and extent of each feedback in addition to considering the temporal scale over which a feedback may be considered irreversible. Juxtaposing the spatial extent of these feedbacks with a map of deforestation enables the identification and discussion of at-risk areas to state changes following deforestation. Last, we discuss the economic implications of these feedbacks and how socioeconomic factors can affect the convergence of a system to a given stable state.

[1] When plants are both sensitive to salt levels in the root zone and able to modify the soil salt balance, changes in vegetation cover may affect the local hydrologic conditions and favor the accumulation of salt within different parts of the soil profile. In such cases a salt-vegetation feedback may exist, whereby both a state with vegetation cover, deep water table, and low salinity and a state with sparse or no vegetation, shallow water table, and high salinity can be stable. In this paper, we develop a modeling framework to relate vegetation-soil salinity feedbacks to the emergence of multiple stable states in the underlying dynamics. This model is used to simulate various scenarios involving changes in forcing parameters of salinity-vegetation dynamics using data from the Murray-Darling Basin. Results show the presence of a strong feedback resulting in bistable dynamics for a wide range of environmental conditions, which has the effect of reducing the resilience of plant ecosystems and the productivity of agricultural systems for areas where such a feedback can occur.

Global Deforestation provides a concise but comprehensive examination of the variety of ways in which deforestation modifies environmental processes, as well as the societal implications of these changes. The book stresses how forest ecosystems may be prone to nearly irreversible degradation. To prevent the loss of important biophysical and socioeconomic functions, forests need to be adequately managed and protected against the increasing demand for agricultural land and forest resources. The book describes the spatial extent of forests, and provides an understanding of the past and present drivers of deforestation. It presents a theoretical background to understand the impacts of deforestation on biodiversity, hydrological functioning, biogeochemical cycling, and climate. It bridges the physical and biological sciences with the social sciences by examining economic impacts and socioeconomic drivers of deforestation. This book will appeal to advanced students, researchers and policymakers in environmental science, ecology, forestry, hydrology, plant science, ecohydrology, and environmental economics.