Ecological pattern and ecosystem theory

This paper considers the central tenet of the 'Econet Initiative' and the developing view of the structure and function of ecosystems and their essential emergence from ecological interactions at the level of individuals and populations. Most of what we consider to be community ecology is concerned with how individuals and species-specific populations respond to, smooth, or fail to accommodate, the consequences of inhabiting continuously variable environments. The essential principle is that individuals, populations, communities, systems, each build towards a definable, contemporaneous, habitat-specific supportive capacity, set by the resource base and the opportunities to process them. While both are amenable, interspecific competition is weak and many species may have the chance to raise their recruitment potential and build biomass, with the dynamic advantage going to the most efficient converters at every trophic level (r- vs. K-selection). As a result of the biomass expansion or of the independent diminution in opportunity or resource base, the special adaptations of disturbance-(R) or stress-(S) tolerant species allow them to glean survival under increasingly competitive strains. Persistent variability and renewal of growth opportunities make exclusion difficult and extinction is more a local than a regional consequence. Poorly competitive species survive through an ability to find new habitat patches 'released' by variability. Integration to larger geographical patterns gives the linkage to higher-order ecosystem behaviour. Some examples of contemporary ecological issues (latitude gradients, optimality, threshold behaviour and the maintenance of biodiversity) are reviewed in the context of systems behaviour. (C) 2002 Elsevier Science B.V. All rights reserved.