On edge- the critical impact of tipping points on the state of a
Topic: Tipping points
by Fed, 2019 Cohort
At its simplest, a tipping point is a critical point at which small changes can cause a system to shift rapidly, drastically, and even permanently, into a different state. Leaning over the side of a canoe, for example, can be a very gradual process. That is, until you lean too far and suddenly it capsizes, illustrating a tipping point. The shift in state, from an upright canoe to a capsized canoe, is considerable.
The rapid, large-scale change that characterises a system once a tipping point is passed is often due to positive feedback mechanisms. A positive feedback mechanism is a loop where the output amplifies the system, which can result in a large increase or decrease in the levels of key conditions. For example, if there are only one or two people on a dance floor, their dancing is not going to induce other people to join in. However, once a critical number of people start dancing there is a tipping point, after which the number of people on the dance floor causes more people to start and their dancing causes even more people to start, and it continues.
Tipping points can occur in various systems, and the nature of the system will determine the difficulty of ‘recovery’; that is, a system returning back to its original state once the tipping point has been crossed.
Recovery is difficult when a system exhibits hysteresis; the situation where once a tipping point is crossed and the system state shifts, a different path must be taken to return to the original state. In figure 2, once tipping point T1 is crossed and state B is entered, the system can’t be returned to state A by restoring initial conditions. Instead, the relevant conditions must be greatly reversed so that tipping point T2 is crossed.
This could be thought of in terms of the one-way lifts in figure 2. In the doorway of lift 1 (a tipping point), stepping forward moves you into the lift, forcing a move to floor B (a new state). In order to return to floor A, you must take a different, longer, path to the bottom of lift 2.
Recovery is easier when a tipping point exists in system that doesn’t exhibit hysteresis. In this kind of system, it is possible to return to an original state, once a tipping point has been passed, by returning the initial conditions.
Recovery is important in environmental systems as it establishes how important it is that conditions be kept below a critical point. For example, if water toxicity in a reef system passes a tipping point at 10% concentration, the reef will shift state from healthy to unhealthy. If the system has no hysteresis, returning the toxicity to below 10% will return the reef to its healthy state. However, if hysteresis is high, this is not the case, and the concentration would have to be reduced much lower than 10%. This would make it highly desirable to avoid reaching the tipping point in the first place.
Disclaimer#
This content has been contributed by a student as part of a learning activity.
If there are inaccuracies, or opportunities for significant improvement on this topic, feedback is welcome on how to improve the resource.
You can improve articles on this topic as a student in "Unravelling Complexity", or by including the amendments in an email to: Chris.Browne@anu.edu.au