How can we tell when an ecosystem is near a tipping point?

Lakes, reefs, forests and drylands can switch abruptly to a different state, such as clear to turbid water or forest to savanna, and often do not switch back easily. Can we see such a shift coming, early enough to act?

Question

How can we tell, from observations, that an ecosystem is approaching a tipping point: a threshold beyond which a small further change in conditions triggers a large and possibly irreversible shift to another state? Signals may come from time series or from spatial patterns.

Background

The question is one of 100 fundamental ecological questions drawn up for the British Ecological Society's centenary from 754 questions submitted by 388 participants. It sits in the theme on ecosystems and functioning, where the authors name predictions about ecosystems undergoing catastrophic transitions as a future challenge [1].

What is known

• Many systems approaching a critical threshold are expected to share generic early-warning signals [2], such as slower recovery from perturbations and rising variance [3].
• In a whole-lake experiment in which top predators were added gradually over three years, with an adjacent lake as reference, warning signals appeared more than a year before the food-web transition was complete [3].
• The error rates of common indicators can be severe even under favourable assumptions; model-based indicators can do better [4].
• Applied to satellite vegetation data for 1991–2016, standard indicators suggest that more than three-quarters of the Amazon rainforest has been losing resilience since the early 2000s, faster where rainfall is lower and human activity closer [5].
• A deep-learning classifier trained on model dynamics near tipping points flagged transitions in 268 empirical and model time series, from ecology to climate and epidemiology, with much greater sensitivity and specificity than generic indicators [6].

What would count as progress

No single result settles a question like this; contributions like these would move it forward:

• An open benchmark of ecological time series that do and do not end in a regime shift (lakes, fisheries, plankton, vegetation), on which indicators are scored for missed signals and false alarms.
• Replicated field or mesocosm experiments that push systems towards a threshold, to test indicators prospectively.
• Indicators applied to satellite records of forests, drylands or reefs, with predictions registered in advance and checked as the systems evolve.

References

1. Sutherland, W. J. et al. (2013). Identification of 100 fundamental ecological questions. Journal of Ecology 101(1), 58–67.
2. Scheffer, M. et al. (2009). Early-warning signals for critical transitions. Nature 461(7260), 53–59.
3. Carpenter, S. R. et al. (2011). Early warnings of regime shifts: a whole-ecosystem experiment. Science 332(6033), 1079–1082.
4. Boettiger, C. & Hastings, A. (2012). Quantifying limits to detection of early warning for critical transitions. Journal of the Royal Society Interface 9(75), 2527–2539.
5. Boulton, C. A., Lenton, T. M. & Boers, N. (2022). Pronounced loss of Amazon rainforest resilience since the early 2000s. Nature Climate Change 12(3), 271–278.
6. Bury, T. M. et al. (2021). Deep learning for early warning signals of tipping points. Proceedings of the National Academy of Sciences 118(39), e2106140118.

Source

Imported from Identification of 100 fundamental ecological questions, question 59, curated by Sutherland et al. Listed as open in the source (2013) and still an active research question as of 2026-10-20. The statement above is written in our own words; see the source for the original wording, history and discussion.