Understanding ecosystem’s response to perturbations is essential to get an
idea of ecological organization and function. May started a debate in 1973. The debate
revolved around ‘stability’ and ‘complexity’ in ecological systems. In the same year, C.
S. Holling in British Columbia came up with imaginative theories of ecosystem
function. Engineering resilience and ecological resilience are two main tenets of his
theory. These theories help us analyze an ecosystem’s response to perturbations; e.g.,
changes in sea surface temperature (SST), other climatic variables, disease and habitat
fragmentation, etc. Ecological systems are complex systems. An idiosyncratic feature of
complex systems is that the whole behaves in an entirely different fashion than the
parts. Concepts and techniques of Newtonian mechanics hardly apply to such systems.
What applies to them is new kind of dynamics called non–linear dynamics. The Chapter
describes all necessary concepts from this discipline. The research on discontinuities in
ecological systems suggests the presence of adaptive cycles across the scales of a
panarchy; a nested set of adaptive cycles operating at discrete levels. A system’s
resilience depends on the interconnections between structure and dynamics at multiple
scales. Complex systems are more resilient when the threshold between a given
dynamic regime and an alternate regime is higher.
Keywords: Structure, Organization, Function, Species diversity, Genetic
diversity, Domain of attraction, Basin of attraction, Information, Entropy,
Perturbations, Climate change, Global ecological change, Integro–differential
equations, Complex systems, Nonlinear Dynamics, Cause and effect, Adaptive
cycles, Panarchy, Resilient systems, Dynamic regime, Multiple scales.
