Rethinking Tipping Points in Spatial Ecosystems

Tipping point theory has garnered substantial attention over recent decades. It predicts abrupt and often irreversible transitions from one ecosystem state to an alternative state. However, ecosystem models that predict tipping typically neglect spatial dynamics. Recent studies reveal that incorporating spatial dynamics may enable ecosystems to evade tipping predicted by nonspatial models. Here, we use a dryland and a savanna-forest model to synthesize mechanisms by which spatial processes can alter the theory of tipping. We further propose that the underlying drivers of positive feedback leading to alternative stable states may provide insight into the tipping evasion mechanisms most relevant to a specific ecosystem. For instance, while positive feedbacks may arise in drylands from direct self-facilitation, such as enhancing the uptake of a limiting resource, at the savanna-forest boundary, it may arise from mutual inhibition between two ecosystem components. In the former case ecosystems can evade tipping by forming self-organized patterns, whereas in the latter the presence of environmental heterogeneity may be required. Our study highlights that deepening our understanding of how ecological feedbacks connect to tipping evasion mechanisms is crucial to formulate better strategies to increase ecosystem resilience.