In contrast to the majority of ecologists, most managers of ecosystems do not understand the importance of experiments in determining mechanisms. In the absence of experimental research, managers and policy-makers must rely on the results of descriptive studies. Unfortunately,these studies often produce conflicting interpretations of underlying
mechanisms and are plagued by weak inference (Platt 1964): descriptive studies (including “natural” experiments, sensu Diamond 1986)are forced to infer mechanism based on pattern. They are, therefore,poorly suited for determining the underlying mechanisms or causes of patterns because there is no test involved (Popper 1981; Keddy 1989).
Even rigorous, long-term monitoring is incapable of revealing causes of change in plant or animal populations because the many factors that potentially contribute to shifts in species composition are confounded (e.g.,Wondzell and Ludwig 1995).