Insect outbreaks annually affect more forest area in temperate and boreal North America than harvesting and wildfire combined. However, the long-term costs and ecosystem consequences of insect outbreaks on forest health and productivity are difficult to quantify, because of the variety of pests involved, the varying scale and severity of the impacts, and the variability in system response to those impacts across geographic regions. Impacts to host species can vary from simple growth reduction to widespread mortality at spatial scales ranging from single trees to entire regions. Resulting changes in wind and light exposure can lead to divergent responses of non host species, varying from increased mortality to growth release. The nonlinear and multi-scaled nature of insect disturbance further limits our ability to forecast ecosystem change in response to outbreak activity. These challenges are underscored by the fact that empirical risk assessments for insect outbreaks typically have low explanatory power and limited spatial domains of applicability, implying that local details and system context are important. Synthesis is needed to better understand and project the short- and long-term consequences of insect disturbance as it influences forest structure and function. Cross-system comparisons should also provide insight into novel responses of forests to insect disturbances within the context of changing climate and land use. This symposium will compare and contrast a suite of otherwise unrelated studies to understand how forests respond to insect outbreaks across pest species, geographic locations, and scales. Presentations are organized to allow comparison among these different factors. For example, we will contrast studies from both the core and fringes of a pest species’ geographic range to begin to tease apart the confounding influences of climate and tree species composition on forest response to outbreaks. Our examples draw primarily from defoliator and bark beetle systems in North America, and include results from both recent studies and new analyses of past datasets. A paper targeting climate effects on biotic disturbances provides the context rather than the theme for the symposium (i.e., one of the main drivers underscoring the need for synthesis). We will conclude with a review and discussion of the papers presented to seek the commonalities and differences among the different insect pest systems and geographic locations in terms of disturbance patterns and their effects on forest productivity and succession.