Regime Shifts – A Global Challenge for the Sustainable Use of Our Marine Resources

Abstract

Over the last decades many marine systems have undergone drastic changes often resulting in new ecologically structured and sometimes economically less valuable states. In particular, the additive effects of anthropogenic stressors (e.g., fishing, climate change) seem to play a fundamental role in causing unexpected and sudden shifts between system states, generally termed regime shifts. Recently, many examples of regime shifts have been documented worldwide and their mechanisms and consequences have been vigorously discussed. Understanding causes and mechanisms of regime shifts is of great importance for the sustainable use of natural resources and their management, especially in marine ecosystems. Hence, we conducted a session entitled "Ecosystem dynamics in a changing world, regime shifts and resilience in marine communities" during the 8th YOUMARES conference (Kiel, 13-15th September 2017) to present regime shifts concepts and examples to a broad range of marine scientists (e.g., biologists and/or ecologists, physicists, climatologists, sociologists) and highlight their importance for the marine ecosystems worldwide. In this chapter, we first provide examples of regime shifts which have occurred over the last decades in our oceans and discuss their potential implications for the sustainable use of marine resources; then we review regime shift theory and associated concepts. Finally, we review recent advances and future challenges to integrate regime shift theory into holistic marine ecosystem-based management approaches.

Status of Marine Biodiversity in the Anthropocene

“…In certain cases, changes in the abundance of different trophic groups can cause significant food web reorganizations (Baum and Worm 2009;Estes et al 2011). Food web reorganizations may manifest as sudden shifts to a new ecosystem state, frequently termed regime shifts (Sguotti and Cormon 2018). Regime shifts are important because alternate ecosystem states can be maintained by internal feedback mechanisms which prevent a system from reverting back to a previous state (Scheffer et al 2001).…”

“…A combination of feedbacks including high juvenile sea urchin abundance, juvenile facilitation by adult sea urchins, and sea urchin-induced mortality of juvenile kelp maintain the system in this new state (Ling et al 2015). These feedbacks mean that even increasing predator abundance to historical highs may not shift the ecosystem back to a macroalgae-dominated state (Sguotti and Cormon 2018). Ecosystems can be resilient to such regime shifts if abundance declines in one species can be compensated by other species in a similar trophic level (Mumby et al 2007).…”

Early Warning from Space for a Few Key Tipping Points in Physical, Biological, and Social-Ecological Systems

“…On the other hand, there are several studies indicating that a single driver, temperature, can be used to predict ecological shifts (Beaugrand 2015;Beaugrand et al 2019), which makes this variable extremely valuable for predictions. In many cases, regime shifts can have large impacts on ecosystem services and on the societies utilizing them (Bellwood et al 2019;Sguotti and Cormon 2018). For example, the phase shifts from coral to algal dominance affect also all ecosystem services provided by the coral reefs (biodiversity, tourism, fishing, and coastal zone protection).…”

Ecological law in the Anthropocene 1

“…A consequence of the non-linearity of ecosystems is that they may not themselves behave in ways indicating that a risk of collapse has arisen before a regime shift occurs (Hastings andWystrom 2010, Scheffer 2015). Indeed, shifts have been known to become apparent only some years after having become unavoidable (Hawkins Bohn andDoncaster 2015, R667, Sguotti andCormon 2018). This presents a particular challenge for regulation whether by reference to prediction of ecological effects or of an ecosystem's likely evolution.…”