Rate-induced tipping in complex high-dimensional ecological networks

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 120; no. 51; p. e2308820120
• Main Authors: Panahi, Shirin, Do, Younghae, Hastings, Alan, Lai, Ying-Cheng
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 19.12.2023
• Subjects: Catastrophic collapse; Drift; Ecological effects; Environmental changes; Initial conditions; Parameters; Scaling laws; rate-induced tipping; tipping point; mutualistic networks; nonlinear dynamics; scaling law
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.2308820120

In an ecosystem, environmental changes as a result of natural and human processes can cause some key parameters of the system to change with time. Depending on how fast such a parameter changes, a tipping point can occur. Existing works on rate-induced tipping, or R-tipping, offered a theoretical way to study this phenomenon but from a local dynamical point of view, revealing, e.g., the existence of a critical rate for some specific initial condition above which a tipping point will occur. As ecosystems are subject to constant disturbances and can drift away from their equilibrium point, it is necessary to study R-tipping from a global perspective in terms of the initial conditions in the entire relevant phase space region. In particular, we introduce the notion of the probability of R-tipping defined for initial conditions taken from the whole relevant phase space. Using a number of real-world, complex mutualistic networks as a paradigm, we find a scaling law between this probability and the rate of parameter change and provide a geometric theory to explain the law. The real-world implication is that even a slow parameter change can lead to a system collapse with catastrophic consequences. In fact, to mitigate the environmental changes by merely slowing down the parameter drift may not always be effective: Only when the rate of parameter change is reduced to practically zero would the tipping be avoided. Our global dynamics approach offers a more complete and physically meaningful way to understand the important phenomenon of R-tipping.