A nonequilibrium thermodynamic framework for discussing ecosystem integrity

During the last 20 years our understanding of the development of complex systems has changed significantly. Two major advancements are catastrophe theory and nonequilibrium thermodynamics with its associated theory of self-organization. These theories indicate that complex system development is nonlinear, discontinuous (catastrophes), not predictable (bifurcations), and multivalued (multiple developmental pathways). Ecosystem development should be expected to exhibit these characteristics.Traditional ecological theory has attempted to describe ecosystem stress response using some simple notions such as stability and resiliency. In fact, stress-response must be characterized by a richer set of concepts. The ability of the system to maintain its current operating point in the face of the stress, must be ascertained. If the system changes operating points, there are several questions to be considered: Is the change along the original developmental pathway or a new one? Is the change organizing or disorganizing? Will the system return to its original state? Will the system flip to some new state in a catastrophic way? Is the change acceptable to humans?The integrity of an ecosystem does not reflect a single characteristic of an ecosystem. The concept of integrity must be seen as multidimensional and encompassing a rich set of ecosystem behaviors. A framework of concepts for discussing integrity is presented in this article.