There is a fundamental difference between the ways in which ecologists and lawyers view uncertainty: in the study of ecology, uncertainty provides a catalyst for exploration, whereas uncertainty is antithetical to the rule of law. This issue is particularly troubling in environmental management, where the tensions between law and ecology become apparent. Rather than acknowledge uncertainties in management actions, legal frameworks often force a false sense of certainty in linking cause and effect. While adaptive management has been developed to deal with uncertainty, laws and legal wrangling can be obstacles to implementation. In this article, we recommend resilience-based governance "adaptive governance" as a means to begin bridging the gap between law and ecology.

Current ecological thinking emphasizes that systems are complex, dynamic, and unpredictable across space and time. What is the diversity in interpretation of these ideas among today's ecologists, and what does this mean for environmental management? This study used a Policy Delphi survey of ecologists to explore their perspectives on a number of current topics in ecology. The results showed general concurrence with nonequilibrium views. There was agreement that disturbance is a widespread, normal feature of ecosystems with historically contingent responses. The importance of recognizing multiple levels of organization and the role of functional diversity in environmental change were also widely acknowledged. Views differed regarding the predictability of successional development, whether "patchiness" is a useful concept, and the benefits of shifting the focus from species to ecosystem processes. Because of their centrality to environmental management, these different views warrant special attention from both managers and ecologists. Such divergence is particularly problematic given widespread concerns regarding the poor linkages between science (here, ecology) and environmental policy and management, which have been attributed to scientific uncertainty and a lack of consensus among scientists, both jeopardizing the transfer of science into management. Several suggestions to help managers deal with these differences are provided, especially the need to interpret broader theory in the context of place-based assessments. The uncertainty created by these differences requires a proactive approach to environmental management, including clearly identifying environmental objectives, careful experimental design, and effective monitoring.

Panarchy focuses on ecological and social systems that change abruptly. Panarchy is the process by which they grow, adapt, transform, and, in the end, collapse. These stages occur at different scales. The back loop of such changes is a critical time and presents critical opportunities for experiment and learning. It is when uncertainties arise and when resilience is tested and established. We now see changes on a global scale that suggest that we are in such a back loop. This article assesses the possibility of using the ideas that are central to panarchy, developed on a regional scale, to help explain the changes that are being brought about on a global scale by the Internet and by climate, economic, and geopolitical changes.

▪ Abstract We review the evidence of regime shifts in terrestrial and aquatic environments in relation to resilience of complex adaptive ecosystems and the functional roles of biological diversity in this context. The evidence reveals that the likelihood of regime shifts may increase when humans reduce resilience by such actions as removing response diversity, removing whole functional groups of species, or removing whole trophic levels; impacting on ecosystems via emissions of waste and pollutants and climate change; and altering the magnitude, frequency, and duration of disturbance regimes. The combined and often synergistic effects of those pressures can make ecosystems more vulnerable to changes that previously could be absorbed. As a consequence, ecosystems may suddenly shift from desired to less desired states in their capacity to generate ecosystem services. Active adaptive management and governance of resilience will be required to sustain desired ecosystem states and transform degraded ecosystems into fundamentally new and more desirable configurations.

Little empirical information exists about how birds respond to urban landscape structure across multiple scales. We explored how the variation in percent tree canopy cover, at four different scales, affected the abundance of bird species across various urban sites in North America. Bird counts were derived from previous studies, and tree patches were measured from aerial photographs that represented areas of 0.2 km2, 1.5 km2, 25.0 km2, and 85.0 km2. At each of the four areas, we conducted regressions between bird counts and percent cover of various tree patch sizes. From these analyses, we determined the area (called the best prediction area—BPA) and the patch size (called the best patch size—BPS) that accounted for a significant amount of the variation in bird counts, beyond the variation accounted for by these parameters measured at other scales. BPA and BPS were calculated primarily to take into account the high degree of collinearity that existed among the amount of tree canopy cover measured across the four scales.

Emerging recognition of two fundamental errors underpinning past polices for natural resource issues heralds awareness of the need for a worldwide fundamental change in thinking and in practice of environmental management. The first error has been an implicit assumption that ecosystem responses to human use are linear, predictable and controllable. The second has been an assumption that human and natural systems can be treated independently. However, evidence that has been accumulating in diverse regions all over the world suggests that natural and social systems behave in nonlinear ways, exhibit marked thresholds in their dynamics, and that social-ecological systems act as strongly coupled, complex and evolving integrated systems. This article is a summary of a report prepared on behalf of the Environmental Advisory Council to the Swedish Government, as input to the process of the World Summit on Sustainable Development (WSSD) in Johannesburg, South Africa in 26 August 4 September 2002. We use the concept of resilience--the capacity to buffer change, learn and develop--as a framework for understanding how to sustain and enhance adaptive capacity in a complex world of rapid transformations. Two useful tools for resilience-building in social-ecological systems are structured scenarios and active adaptive management. These tools require and facilitate a social context with flexible and open institutions and multi-level governance systems that allow for learning and increase adaptive capacity without foreclosing future development options.

The five articles in this special feature extend the discovery of regular patterns of deviation from scaling laws and from continuous distributions of attributes in ecosystems and other complex systems. These patterns suggest that these systems organize over discrete ranges of scale and that organization abruptly shifts with changes in scale. If this is so, scaling laws (for example, see West 1997, 1999; Zipf 1949) serve only as the baseline from which to measure those departures, and those departures indicate “scale breaks” (transitions) between scales of structure in complex systems. Patterns in the deviations from a scaling-law baseline may provide hints of the processes that cause the emergence of the scaling relationships themselves. At minimum, the investigation of departures from scaling laws gives us a clue into the nature of structure and process in ecological systems. Ecosystems may be structured by relatively few key processes, each operating at specific temporal and spatial scales (Carpenter and Leavitt 1991; Levin 1992). The distinct temporal frequencies and spatial scale characterizing these processes creates landscape structures with scale-specific pattern (Burrough 1981; O’Neill and others 1991; Milne and others 1992). This may in turn entrain attributes of animals residing on the landscape (Holling 1992) because different-sized animals living upon the same landscape perceive their environment at different scales (Milne and others 1989; Holling 1992; Peterson and others 1998) (Figure 1). Holling (1992) suggested that this entrainment reflects adaptations to the discontinuous pattern of resource distribution acting through animal community assembly and evolution, both by sorting species and by providing a specific set of evolutionary opportunities and constraints. On the animal community level, this should be expressed by a discontinuous distribution of species body masses (Holling 1992). Within a system, aggregations of species body masses are separated by discrete breaks (or discontinuities) separating different ranges of scale. Animals within a particular body mass aggregation perceive and exploit the environment at the same range of scale (Peterson and others 1998) (Figure 2). Holling’s proposition that ecosystem structure entrains attributes of animals—such as body mass distributions (the textural discontinuity hypothesis)—was received with some skepticism, but also with interest. It is now generally accepted that many attributes of ecosystems are discontinuously distributed, but mechanisms other than entrainment by ecological structure (Brown 1995) have been proposed. However, most of the disagreements with Holling’s proposition have been technical, focusing on the methods used to detect discontinuities (Manly 1996; Siemann and Brown 1999). New evidence for a link between landscape structure at different scales and body mass distributions has provided support for the textural discontinuity hypothesis. Discontinuous body mass patterns have been documented in many systems (see for example, Holling 1992; Restrepo and others 1997; Lambert and Holling 1998; Allen and others 1999; RafReceived 25 January 2002; accepted 28 January 2002. *Corresponding author; e-mail: allencr@clemson.edu Ecosystems (2002) 5: 315–318 DOI: 10.1007/s10021-001-0075-3 ECOSYSTEMS

Strong inference is a powerful and rapid tool that can be used to identify and explain patterns in molecular biology, cell biology, and physiology. it is effective where causes are single and separable and where discrimination between pairwise alternative hypotheses can be determined experimentally by a simple yes or no answer. But causes in ecological systems are multiple and overlapping and are not entirely separable. Frequently, competing hypotheses cannot be distinguished by a single unambiguous test, but only by a suite of tests of different kinds, that produce a body of evidence to support one line of argument and not others. We call this process "adaptive inference". Instead of pitting each member of a pair of hypotheses against each other, adaptive inference relies on the exuberant invention of multiple, competing hypotheses, after which carefully structured comparative data are used to explore the logical consequences of each. Herein we present an example that demonstrates the attributes of adaptive inference that have developed out of a 30-year study of the resilience of ecosystems.