Recovery rates reflect distance to a tipping point in a living system

• Published in: Nature (London) Vol. 481; no. 7381; pp. 357 - 359
• Main Authors: Veraart, Annelies J., Faassen, Elisabeth J., Dakos, Vasilis, van Nes, Egbert H., Lürling, Miquel, Scheffer, Marten
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 19.01.2012; Nature Publishing Group
• Subjects: 631/158/2445; 631/57/2272/2275; 704/106; Animal and plant ecology; Animal, plant and microbial ecology; Biological and medical sciences; Biomass; communities; competition; Cyanobacteria - growth & development; Cyanobacteria - radiation effects; Demecology; ecosystems; Environmental Sciences; Feedback - radiation effects; Fundamental and applied biological sciences. Psychology; Humanities and Social Sciences; Kinetics; letter; Light; Models, Biological; multidisciplinary; Noise; Perturbation (Astronomy); Photosynthesis - radiation effects; Plants and fungi; Science; Science (multidisciplinary); shifts; slowing-down; Stochastic Processes; Studies; Trends; United States; Environmental factor; Biomass; Perturbation; Recovery; Biological productivity; Population productivity; Freshwater environment; Luminous intensity; Cyanobacteria; Living system; Bacteria; Phytoplankton; Population; Aphanizomenon flosaquae
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature10723

Decreased rates of recovery from perturbations, or critical slowing down, are demonstrated in a living system, indicating that recovery rates can be used to probe the resilience of complex systems. Predicting the tipping point Complex systems as different as the brain, ecosystems, financial markets and climate can have tipping points at which a minor perturbation provokes transition to a contrasting dynamic state. The value of being able to predict such points is obvious. One possible sign of change is a concept familiar in physics, known as 'critical slowing down'. Experiments in which cyanobacterial microcosms were subjected to perturbation suggest that critical slowing down does occur, and that recovery rates can be used to gauge the resilience of complex systems. Tipping points, at which complex systems can shift abruptly from one state to another, are notoriously difficult to predict 1 . Theory proposes that early warning signals may be based on the phenomenon that recovery rates from small perturbations should tend to zero when approaching a tipping point 2 , 3 ; however, evidence that this happens in living systems is lacking. Here we test such ‘critical slowing down’ using a microcosm in which photo-inhibition drives a cyanobacterial population to a classical tipping point when a critical light level is exceeded. We show that over a large range of conditions, recovery from small perturbations becomes slower as the system comes closer to the critical point. In addition, autocorrelation in the subtle fluctuations of the system’s state rose towards the tipping point, supporting the idea that this metric can be used as an indirect indicator of slowing down 4 , 5 . Although stochasticity prohibits prediction of the timing of critical transitions, our results suggest that indicators of slowing down may be used to rank complex systems on a broad scale from resilient to fragile.