Embracing thresholds for better environmental management

Abstract

Three decades of study have revealed dozens of examples in which natural systems have crossed biophysical thresholds (‘tipping points’)—nonlinear changes in ecosystem structure and function—as a result of human-induced stressors, dramatically altering ecosystem function and services. Environmental management that avoids such thresholds could prevent severe social, economic and environmental impacts. Here, we review management measures implemented in ecological systems that have thresholds. Using Ostrom's social–ecological systems framework, we analysed key biophysical and institutional factors associated with 51 social–ecological systems and associated management regimes, and related these to management success defined by ecological outcomes. We categorized cases as instances of prospective or retrospective management, based upon whether management aimed to avoid a threshold or to restore systems that have crossed a threshold. We find that smaller systems are more amenable to threshold-based management, that routine monitoring is associated with successful avoidance of thresholds and recovery after thresholds have been crossed, and that success is associated with the explicit threshold-based management. These findings are powerful evidence for the policy relevance of information on ecological thresholds across a wide range of ecosystems.

A holistic view of marine regime shifts

“…Eventually, information and knowledge on environmental thresholds is a further critical component to management success [99]. Management consideration of environmental thresholds appears to be scale-dependent and is more effective at smaller scales.…”

“…Hence, a spatially nested approach, i.e. a common largescale framework with nested spatial authorities, may provide an optimal balance between the large scale of marine ecosystems and the small scale of effective governance [99]. The worldwide scale of global fishing activities, with its potential role in driving marine regime shifts [100], presents a relevant case study for such a spatially nested management approach.…”

Social Information Links Individual Behavior to Population and Community Dynamics

“…To gain a qualitative understanding of how social information could manifest itself, we take a simplified view by considering cases where the benefits of social information outweigh competitive costs only at low population densities (i.e., when competition would be relatively low) (see Figure I in Box 2). Even over narrow density ranges, positive density dependence driven by social information can cause populations to experience critical thresholds, which, though believed to be common in nature, are often difficult to identify or predict [50][51][52] Social information can further influence the relationship between population growth rate and density by altering the self-regulation of a population. Benefits of additional social information can saturate because of the inherent redundancy of repeated information concerning a stimulus or because information about a stimulus (e.g., a food patch) might be accurate for less time in crowded conditions [4,21,22,28,30] (Box 2).…”

Navigating Critical Thresholds in Natural Resource Management: A Case Study of Olympic National Park

“…The uncertainty and irreversibility associated with crossing ecological thresholds requires a better understanding of how and when systems switch from one state to another. Kelly et al (2015) argue that "until recently, the primary way in which management has incorporated thresholds into permitting, planning or other regulatory decisions has been retrospective, i.e., only after the threshold is crossed does its existence become relevant to policy." Waiting for thresholds to be crossed poses significant threats to ecological systems and species.…”