The spruce budworm This example relates to management of North American forest subject to periodic outbreaks of the spruce budworm (Chorisoneuma fumiferana). This important lepidopteran defoliator of conifers is responsible for tremendous damage to North American forests. Mature forest stands dominated by balsam fir (Abies balsamea) are believed to be particularly vulnerable to budworm outbreaks, but stands of white spruce (Picea glauca) and red spruce (P. rubens) may also suffer substantial damage. An outbreak may kill up to 75-90% of trees in a fir stand, whereas impacts on spruce are less catastrophic. Only small trees usually survive budworm infestation. When the epidemic episode dies out, young understory trees enter a series of successional stages, at the end of which a new mature community of fir and spruce is reestablished. This stand is again susceptible to anew outbreak that can eventually wipe out part of the forest and start a new trend of successional phases. The dynamic of the budworm-forest system thus can be viewed as a cyclic succession with long-term dynamic stability (Freedman 1995). Outbreaks of budworm have probably recurred on the landscape for thousands of years (Baskerville 1975, MacLean and Erdle 1984, Blais 1985, Freedman 1995). After the second World War, however, as a way to cope with this resource crisis, considerable effort was devoted to controlling budworm outbreaks by intensive spreading of insecticide. Initially, this policy led to higher biomass production by constraining the budworm population, limiting defoliation, and substantially reducing tree mortality. Eventually, it promoted an increasingly large biomass of susceptible tree species, mainly dominated by mature stands of balsam fir and white spruce. Since 1974, insecticide spraying has not been effective in controlling budworms; in subsequent years, an outbreak has covered an area of an extent and intensity never experienced before. On the basis of this experience, Clark et al. (1979) have devised an instructive lesson for ecologically sound policy design that enables resource managers to account explicitly for natural variability, spatial heterogeneity, and nonlinear causation due to the combination of the multiscale, dynamical mechanisms of the exploited ecosystem.