How do ecosystems respond to external perturbations?

This paper attempts to study the influence of environmental perturbations on evolutionary modes (dynamical regimes) of model ecosystems. Three model systems are analysed and the relative importance of these modes is depicted in basin boundary structures. It is found that sudden perturbations usually influence these modes significantly. The coexistence of two or more distinct attractors on the same set of parametric values in nonlinear dynamical systems suggests that the environmental forces may alter the dynamical regimes of these systems. Two-dimensional parameter scans suggest that even smooth (periodic or seasonal) perturbations, which bring changes in system parameters and thus decide dynamical modes to be displayed in a particular situation, are able to induce variations in these modes. It should be noted that the nature of changes induced by the two types of perturbations is different. While the former causes predictable changes in the dynamical modes, the latter forces the system to meander among different dynamical regimes aimlessly. The present study indicates that the influences of sudden (unforeseen) perturbations (e.g., forest fire, drought, flood, invasion by exotic species, etc.) on the ecosystem dynamics can be controlled provided the systemʹs dynamic complexity is understood properly. The knowledge of these influences may help us in gaining insight into how ecological disasters can be managed.