Managing for resilience with ecological structure: Portfolio effects in the Laurentian Great Lakes

Abstract

Combined effects of global change, including land conversion, biological invasions, and overexploitation, have degraded the resilience of ecosystems and the services they provide. Here, we identify key ecological structures and processes that can be targeted by management to improve resilience at scales ranging from single species to entire landscapes. We highlight portfolio effects as a resilience-promoting process that both stabilizes and increases yield within food webs. We then discuss how habitat heterogeneity propagates portfolio effects across trophic levels and spatial scales to generate resilient ecosystems. Using examples from the North American Great Lakes Basin, we show that human-driven global change has broadly eroded portfolio effects and habitat heterogeneity, thereby increasing ecosystem vulnerability to future disturbances. Fortunately, strategic management actions can amplify resilience-promoting processes and dampen instabilities. Our synthesis supports the incorporation of whole-ecosystem resilience indices into conventional natural resource management and the structured, landscape-scale restoration of habitat heterogeneity to promote across-scale portfolio effects.