Figure 1.

Stability regimes of naturally occurring ecosystems. (a) Reversible linear: the system goes through incremental deterioration following increasing stress, but it is reversible along the same trajectory if the insult goes back to the initial level. (b) Threshold-dependent, nonlinear behaviour: upon exposure to enough pressure, the system moves from one operational state to a non-functioning regime—but it can return to normal when the burden ceases. (c) Nonlinear threshold-dependent with catastrophic fold bifurcation. In this scenario, stress makes the system reach a tipping point followed by irreversibly running into a complete shift of regime [5]. In this case, decreasing the pressure is not enough for returning to the sustainable functioning zone.