Identifying the tipping points of recovering ecological systems

Environmental changes, such as those caused by climate or land use change, can cause ecosystems to tip, or shift from one stable state to another. These perturbations are known as pulses when they occur as intense events, such as heat waves or severe rain.

Basak et al. investigated how two sequential pulses affect tipping in a population model of spruce budworms. This population is bistable, with low- and high-population density states. The low-population state is better for the forest.

The authors applied two successive pulses to the spruce budworm model that diminish the growth conditions for this species. Depending on the intensity and timescale of the first pulse, the system either tipped or returned to its original state. But they found the second pulse could tip the recovered system if it occurred soon after the first pulse, even if it is too weak to tip the system by itself.

“We show that the intricate interplay of the different timescales in the system, the rate of environmental change and the intrinsic ecological time scale, can lead to a tipping,” said author Ulrike Feudel. “As a consequence, the history of perturbations plays a decisive role for a possible tipping of the ecosystem.”

This work suggests that taking appropriate measures at the right time may prevent an ecosystem from unexpectedly tipping after a second extreme environmental event, especially those related to climate change.

“This analysis, which is inspired by experimental setups to study the impact of climate change on ecosystems, is fundamentally different to the well-studied influence of environmental fluctuations,” Feudel said.

Source: “When do multiple pulses of environmental variation trigger tipping in an ecological system?,” by Ayanava Basak, Syamal K. Dana, Nandadulal Bairagi, and Ulrike Feudel, Chaos (2024). The article can be accessed at https://doi.org/10.1063/5.0205410 .

This paper is part of the Nonautonomous Dynamical Systems: Theory, Methods, and Applications collection, learn more here .