Natural regulation of ecosystems in protected areas as ecological baselines

Ecological baseline areas are necessary benchmarks to detect slow change and predict fast change in ecosystems that humans depend upon. National parks, by default, fulfill this role provided they are large enough to maintain natural processes. They should be used to understand natural regulatory ecosystem processes that are then compared with other human-dominated systems. Natural regulation operates through negative feedback mechanisms in reproduction or mortality caused by factors such as food shortage and predation. Protected areas are capable of self-regulation as evidenced by many studies of such ecosystems covering several decades. They exhibit natural change, often with periodicities of decades or centuries, and such change must be accommodated in management plans. Ecosystems exhibit >1 natural state, often as a result of top-down processes such as predation and herbivory. These multistates are identified by their irreversibility when the cause of perturbations is removed. They are characterized by >1 combination of population densities and species. Predators may or may not be present, and herbivores may or may not impinge on the vegetation. Therefore, there is no single combination of species or ecosystem states for which management should strive. Naturalness, per se, is not the objective. Rather, the fundamental need is to compare ecosystems experiencing modern human impact with those in protected areas that are relatively free of such impacts so as to understand their consequences for mankind. The presence or absence of prehistoric humans is not relevant to these objectives. Management, however, should act to minimize disturbances, such as the presence of exotic species, within these ecological baselines. Monitoring of ecosystem change should be coordinated on a global basis, using simple and robust techniques.