Ecosystem stewardship is an action-oriented framework intended to foster social-ecological sustainability of a rapidly changing planet. Recent developments identify three strategies that make optimal use of current understanding in an environment of inevitable uncertainty and abrupt change: reducing the magnitude of, and exposure and sensitivity to, known stresses; focusing on proactive policies that shape change; and avoiding or escaping unsustainable socialecological traps. All social-ecological systems are vulnerable to recent and projected changes but have sources of adaptive capacity and resilience that can sustain ecosystem services and human well-being through active ecosystem stewardship. A Call for Ecosystem StewardshipHuman actions are having large and accelerating effects on Earth's climate, environment, and ecosystems 1, 2 , thereby degrading many ecosystem services (see glossary) 3 . This unsustainable 2 trajectory demands a dramatic change in human relationships with the environment and lifesupport system of the planet 2,3 . In this paper we address recent developments in thinking about the sustainable use of ecosystems and resources by society in the context of rapid and frequently abrupt change (Box 1).Western resource management paradigms have evolved from exploitation, where sustainability is not an important consideration, to steady-state resource management aimed at maximum or optimum sustainable yield (MSY or OSY, respectively) and efficient production of a single resource such as fish or trees, to ecosystem management to sustain a broader suite of ecosystem services 4 ( Fig. 1). Despite its sustainability goal, management for MSY or OSY tends to over-exploit targeted resources because of overly optimistic assumptions about the capacity to sustain productivity, avoid disturbances, regulate harvesters' behavior, and anticipate extreme economic or environmental events 5 . Ecosystem management seeks to sustain multiple ecosystem services 6 but often uses, as a reference point, historic conditions that are not achievable in a rapidly changing world.Given the challenges of sustainable use of ecosystems during rapid change, we advocate a shift to ecosystem stewardship (Table 1) 7,8 . Its central goal is to sustain the capacity to provide ecosystem services that support human well-being under conditions of uncertainty and change (see glossary). Uncertainty has always characterized social-ecological systems and should therefore not be an impediment to action. Such a paradigm shift entails important tradeoffs, particularly between efficiency and flexibility and between immediate and long-term benefits 9, 10 .Ecosystem stewardship integrates three broadly overlapping sustainability approaches 8,11, 12 (Fig. 2): reducing vulnerability to expected changes [11][12][13] ; fostering resilience to sustain 3 desirable conditions in the face of perturbations and uncertainty 14 ; and transforming from undesirable trajectories when opportunities emerge 15,16 . Adaptive capacity contributes to all three ...

No abstract

No abstract

No abstract

Ecological studies of terrestrial urban systems have been approached along several kinds of contrasts: ecology in as opposed to ecology of cities; biogeochemical compared to organismal perspectives, land use planning versus biological, and disciplinary versus interdisciplinary. In order to point out how urban ecological studies are poised for significant integration, we review key aspects of these disparate literatures. We emphasize an open definition of urban systems that accounts for the exchanges of material and influence between cities and surrounding landscapes. Research on ecology in urban systems highlights the nature of the physical environment, including urban climate, hydrology, and soils. Biotic research has studied flora, fauna, and vegetation, including trophic effects of wildlife and pets. Unexpected interactions among soil chemistry, leaf litter quality, and exotic invertebrates exemplify the novel kinds of interactions that can occur in urban systems. Vegetation and faunal responses suggest that the configuration of spatial heterogeneity is especially important in urban systems. This insight parallels the concern in the literature on the ecological dimensions of land use planning. The contrasting approach of ecology of cities has used a strategy of biogeochemical budgets, ecological footprints, and summaries of citywide species richness. Contemporary ecosystem approaches have begun to integrate organismal, * The U.S. Government has the right to retain a nonexclusive, royalty-free license in and to any copyright covering this paper.