Using Ecological Thresholds to Inform Resource Management: Current Options and Future Possibilities

Abstract

In the face of growing human impacts on ecosystems, scientists and managers recognize the need to better understand thresholds and non-linear dynamics in ecological systems to help set management targets. However, our understanding of the factors that drive threshold dynamics, and when and how rapidly thresholds will be crossed is currently limited in many systems. In spite of these limitations, there are approaches available to practitioners today-including ecosystem monitoring, statistical methods to identify thresholds and indicators, and threshold-based adaptive management-that can be used to help avoid reaching ecological thresholds or restore systems that have crossed them. We briefly review the current state of knowledge and then use real-world examples to demonstrate how resource managers can use available approaches to avoid crossing ecological thresholds. We also highlight new tools and indicators being developed that have the potential to enhance our ability to detect change, predict when a system is approaching an ecological threshold, or restore systems that have already crossed a tipping point.

Modelling fishery induced impacts on the food web of the continental shelf off central south Chile using a size based network approach

“…Suggesting the existence of thresholds that need to be examined further. Those indicators are less informative for fisheries management once the fishery has developed, but those thresholds can provide a useful early warning system for newly established fisheries where the target community has not yet been affected (Mullon et al, 2005;McClanahan et al, 2011;Foley et al, 2015). The lack of responsiveness of these indicators beyond a certain level of fishing impact may suggest that beyond those ecological thresholds the ecosystem may reach a point of no return, or a shift to an alternative ecosystem phase, i.e., an overexploited state (sensu Scheffer & Carpenter, 2003;Knowlton, 2004).…”

Comparing Apples to Oranges: Common Trends and Thresholds in Anthropogenic and Environmental Pressures across Multiple Marine Ecosystems

“…The methods presented here are complex, in terms of statistical analyses, but are able to offer clear ecosystem-level outputs of threshold ranges across pressure gradients. As such, thresholds provide a powerful tool to delineate and communicate quantifiable tipping points for ecosystems (Foley et al, 2015).…”

“…There is a convergence of knowledge in multiple disciplines (social sciences, economics, ecology, oceanography) in current EBM research that aims to quantify this socio-ecological "sweet spot" (Levin et al, 2009;Link, 2010;Samhouri et al, 2012). While there is a great deal of interdisciplinary work being done in marine ecosystem science, there is a relatively limited set of comparative studies of ecosystem-level trends and thresholds-based reference points (e.g., Murawski et al, 2010;Samhouri et al, 2010Samhouri et al, , 2017Large et al, 2013Large et al, , 2015aFoley et al, 2015;Link et al, 2015;Connell et al, in press) which are required to fully assess the ability of ecosystem science to effectively manage large marine ecosystems.…”

“…More recently, there has been a shift toward thresholds-based reference points as an alternative to traditionally developed baselines (Samhouri et al, 2010;Large et al, 2013Large et al, , 2015aFoley et al, 2015). Thresholds are derived from pressure-response relationships and are akin to LD 50 in toxicology studies where at some point along a pressure gradient (chemical or otherwise) organisms experience a median negative impact (Samhouri et al, 2010).…”

“…Thresholds are derived from pressure-response relationships and are akin to LD 50 in toxicology studies where at some point along a pressure gradient (chemical or otherwise) organisms experience a median negative impact (Samhouri et al, 2010). Ecosystem thresholds can help to develop non-arbitrary targets and guide management actions that avoid unwanted shifts in ecosystem state (Samhouri et al, 2011;Foley et al, 2015). Already, there are a number of international efforts that aim to conduct EBM in shared marine spatial domains including the European Union Marine Strategy Framework Directive (Palialexis et al, 2014;Bigagli, 2015;Tam et al, in press) and the Convention for the Conservation of Antarctic Living Marine Resources (Constable et al, 2000;Constable, 2011).…”