Overfishing reduces resilience of kelp beds to climate-driven catastrophic phase shift

Ling, S. D., et al., 2009. Proceedings of the National Academy of Sciences of the United States of America

Original research (primary data)
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A key consideration in assessing impacts of climate change is the possibility of synergistic effects with other human-induced stressors. In the ocean realm, climate change and overfishing pose two of the greatest challenges to the structure and functioning of marine ecosystems. In eastern Tasmania, temperate coastal waters are warming at approximately four times the global ocean warming average, representing the fastest rate of warming in the Southern Hemisphere. This has driven range extension of the ecologically important long-spined sea urchin (Centrostephanus rodgersii), which has now commenced catastrophic overgrazing of productive Tasmanian kelp beds leading to loss of biodiversity and important rocky reef ecosystem services. Coincident with the overgrazing is heavy fishing of reef-based predators including the spiny lobster Jasus edwardsii. By conducting experiments inside and outside Marine Protected Areas we show that fishing, by removing large predatory lobsters, has reduced the resilience of kelp beds against the climate-driven threat of the sea urchin and thus increased risk of catastrophic shift to widespread sea urchin barrens. This shows that interactions between multiple humaninduced stressors can exacerbate nonlinear responses of ecosystems to climate change and limit the adaptive capacity of these systems. Management actions focused on reducing the risk of catastrophic phase shift in ecosystems are particularly urgent in the face of ongoing warming and unprecedented levels of predator removal from the world’s oceans.

Case studies

Basic information

  • Case ID: INT-137-1
  • Intervention type: Protection
  • Intervention description:

    Marine protected areas (established 12 and 31 years before experiment for the two different sites respectively)

  • Landscape/sea scape ecosystem management: Yes
  • Climate change impacts Effect of Nbs on CCI Effect measures
    Increased pests  Positive Survivorship of Centrostephanus rodgersii (pest)
  • Approach implemented in the field: Yes
  • Specific location:

    The Maria Island Marine Reserve (MIMR, 42° 35.26 S, 148° 3.03 E) and the Crayfish Point Research Reserve (CPRR, 42° 57.37 S, 147° 21.30 E) (the intervention sites) and adjacent fished sites (the control sites)

  • Country: Australia
  • Habitat/Biome type: Temperate oceans |
  • Issue specific term: Not applicable


  • Notes on intervention effectivness: effectiveness determined by comparing to adjacent fished/unprotected (i.e. control) sites. outcome relevant for ecosystems as well because the pest is also having a negative effect on biodiversity in general
  • Is the assessment original?: Yes
  • Broadtype of intervention considered: Not applicable
  • Compare effectivness?: No
  • Compared to the non-NBS approach: Not applicable
  • Report greenhouse gas mitigation?: No
  • Impacts on GHG: Not applicable
  • Assess outcomes of the intervention on natural ecosystems: Yes
  • Impacts for the ecosystem: Positive
  • Ecosystem measures: % survivorship of Centrostephanus rodgersii
  • Assess outcomes of the intervention on people: No
  • Impacts for people: Not reported
  • People measures:
  • Considers economic costs: No
  • Economic appraisal conducted: No
  • Economic appraisal described:
  • Economic costs of alternative considered: No
  • Compared to an alternative: Not reported

Evaluation methodology

  • Type of data: Quantitative
  • Is it experimental: Yes
  • Experimental evalution done: In-situ/field
  • Non-experimental evalution done: Not applicable
  • Study is systematic: