Global regime shift dynamics of catastrophic sea urchin overgrazing

By S. Ling, R. Scheibling, A. Rassweiler, Craig R. Johnson, Nick T. Shears, S. Connell, A. Salomon, K. Norderhaug, A. Pérez‐Matus, J. Hernández and 10 more. Philosophical Transactions of the Royal Society B: Biological Sciences, 2015

517 citations recorded by the source corpus.

A pronounced, widespread and persistent regime shift among marine ecosystems is observable on temperate rocky reefs as a result of sea urchin overgrazing. Here, we empirically define regime-shift dynamics for this grazing system which transitions between productive macroalgal beds and impoverished urchin barrens. Catastrophic in nature, urchin overgrazing in a well-studied Australian system demonstrates a discontinuous regime shift, which is of particular management concern as recovery of desirable macroalgal beds requires reducing grazers to well below the initial threshold of overgrazing. Generality of this regime-shift dynamic is explored across 13 rocky reef systems (spanning 11 different regions from both hemispheres) by compiling available survey data (totalling 10 901 quadrats surveyed in situ) plus experimental regime-shift responses (observed during a total of 57 in situ manipulations). The emergent and globally coherent pattern shows urchin grazing to cause a discontinuous ‘catastrophic’ regime shift, with hysteresis effect of approximately one order of magnitude in urchin biomass between critical thresholds of overgrazing and recovery. Different life-history traits appear to create asymmetry in the pace of overgrazing versus recovery. Once shifted, strong feedback mechanisms provide resilience for each alternative state thus defining the catastrophic nature of this regime shift. Importantly, human-derived stressors can act to erode resilience of desirable macroalgal beds while strengthening resilience of urchin barrens, thus exacerbating the risk, spatial extent and irreversibility of an unwanted regime shift for marine ecosystems.

Subfields: Ecology, Oceanography

View Paper: https://www.semanticscholar.org/paper/83ef23d2a5db2acf84d29e0bcd91296095a0aacc

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Ecology

1. T. Wernberg
2. Dan A. Smale
3. Pippa J. Moore
4. S. Connell
5. S. Hawkins
6. H. Teagle
7. S. Ling
8. J. Vásquez

In Oceanography

1. T. Wernberg
2. Dan A. Smale
3. Pippa J. Moore
4. S. Connell
5. S. Hawkins
6. J. Vásquez
7. H. Teagle
8. S. Ling

Citations in the corpus

• Regime shifts in exploited marine food webs: detecting mechanisms underlying alternative stable states using size-structured community dynamics theory (2015, background): “The presence of alternative states stabilized by internal feedbacks has been suggested to explain the lack of recovery of overgrazed kelp beds [7], overgrown coral reefs [8] and overexploited top predatory fish [9,10].”
• Global patterns of kelp forest change over the past half-century (2016, background): “Regional variation in the trajectories of kelp change was also influenced by the underlying frequency of sea urchin-driven phase shifts that characterize many kelp forest ecosystems (28, 30).”
• Enhancing climate change resilience of ecological restoration — A framework for action (2021, background): “The poleward expansion of the sea urchin Centrostephanus rodgersii, for instance, is linked to increased sea surface temperatures, resulting in catastrophic shifts from seaweed dominated reefs to sea urchin dominated barrens in Tasmania, Australia (Ling et al., 2015).”
• The role of kelp species as biogenic habitat formers in coastal marine ecosystems (2017, background): “…loss of biogenic 752 habitat from temperate ecosystems, in extreme cases causing phase-shifts from structurally complex 753 habitat to depauperate “barrens” (Breen and Mann, 1976b; Filbee-Dexter and Scheibling, 2014; 754 Hagan, 1983; Johnson et al., 2011; Ling et al., 2015; Steneck et al., 2002).”
• Scientists’ warning to humanity: microorganisms and climate change (2019, unknown): “As sea stars are important predators of sea urchins, loss of predation can cause a trophic cascade that affects kelp forests and associated marine biodiversity 229,230 .”
• Resilience indicators: prospects and limitations for early warnings of regime shifts (2015, background): “Subsequent studies suggested a similar potential of shifting between alternative states (or ‘regimes’) also in coral reefs [4,5], kelp forests [6,7], macroalgae beds [8], fish populations [9–11], and even whole pelagic and benthic communities [12–16].”