A review of environmental droughts: Increased risk under global warming?

This article reviews current drought effects on environmental systems. It stresses the need for considering environmental drought as a relevant type to be included in drought classifications. Here we illustrate that drought has complex environmental effects and affects many different systems (e.g., soils, air, vegetation, and forests, aquatic systems and wildlife). Droughts can affect the quality, structure, and diversity of these systems. However, we find that most environmental systems show strong resistance and resilience to drought events, and the effects of drought are usually temporary. Structural effects of environmental droughts tend to only occur in areas that are perturbed or in communities near their distribution limits. There are few long-term experimental studies that quantify possible trends in drought effects on environmental systems. Nevertheless, existing studies of forests that are based on tree-ring chronologies or forest inventories indicate increased drought-related effects on environmental systems. Future climate change scenarios suggest increased drought severity worldwide, which could alter the vulnerability of different environmental systems and increase the number of structural drought effects.