Nonlinear Dynamics and Chaos

Throughout much of ecology’s history, most ecologists have believed that ecological systems tend towards an equilibrium – a notion popularized as ‘the balance of nature’ – and that deviations from that equilibrium are caused by external perturbations. By assuming that systemswere close to equilibrium, ecologists coulddescribe them with linear models that were mathematically tractable. However, ecology is rife with processes whose rates depend nonlinearly on the state of the system – such as nutrient uptake, density dependence and predation. Advances in computing power and availability in the 1970s led to the discovery that such nonlinearities could cause spontaneous oscillations. Interest initially focused on chaos as a potential explanation for all of the irregular fluctuations in nature. Two decades of investigation suggest that ecological chaos is rare in natural systems – ecology really is ‘noisy’. Nevertheless, the importance of nonlinear processes, and the resulting nonequilibrium dynamics, are now fully accepted at the core of ecology.