By: Bland, L.M., Regan, T.J., Dinh, M.N., Ferrari, R., Keith, D.A., Lester, R., Mouillot, D., Murray, N.J., Nguyen, H.A. & Nicholson, E.

In: Proceedings of the Royal Society B: Biological Sciences (284)  [link]

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Ecosystems around the world face degradation and collapse as a result of environmental and human-induced changes. Ecosystem collapse may involve large losses of biodiversity, ecosystem functions and services, as well as impacts on human well-being. Understanding the risk that ecosystem collapses will occur is a fundamental requisite for conservation planning and adaptation to environmental change. Effective ecosystem risk assessment relies on a conceptual understanding of how ecosystems function, and the synthesis of multiple lines of evidence. Risk assessment protocols and ecosystem models integrate limited observational data with threat scenarios, making them valuable tools for monitoring ecosystem status and diagnosing key mechanisms of decline to be addressed by management.

(Images courtesy of  Dr. Renata Ferrari @DrFerrariR )

Coral reefs are biologically and economically, and vulnerable to a range of interacting threats, including climate change. Here we assessed the risk of collapse of the Meso-American Reef, a unique ecosystem containing the second longest barrier reef in the world. We use a ‘whole-of-ecosystem’ model, the Coral Reef Scenario Evaluation Tool, to assess risks to the Meso-American Reef (MAR). The MAR contains the second longest barrier reef in the world, and extends more than 1000 km from Mexico to Belize, Guatemala and northern Honduras. The MAR has been affected by multiple threats over the last 50 years, including hurricanes, lionfish invasion, overfishing, pollution, ocean acidification, rising sea surface temperatures, and disease outbreaks among urchins and corals. As in many coral reefs around the world, threats are predicted to increase in the future, so there is an urgent need to understand interactions among threats and evaluate potential levers for management.

We applied the criteria and framework of the IUCN (International Union for the Conservation of Nature) Red List of Ecosystems to assess the risk of collapse. The IUCN Red List of Ecosystems is the global standard for assessing risks to ecosystems, based on changing distribution and function. We collated a wide array of empirical data (field and remotely sensed), and used a stochastic ecosystem model to reconstruct past ecosystem dynamics, as well as forecast future ecosystem dynamics under 11 scenarios of threat. The ecosystem is at high risk from mass bleaching in the coming decades, with compounding effects of ocean acidification, hurricanes, pollution and fishing. The overall status of the ecosystem is Critically Endangered.

Our case study provides a template for assessing risks to coral reefs and for further application of ecosystem models in risk assessment. This is particularly important as the global conservation community looks towards assessing risks to coral reefs around the world, along with the species and ecosystem services they provide. With recent mass bleaching events across coral reefs, including the Great Barrier Reef, identifying those areas most at risk, and diagnosing how they can be managed, is critical to our understanding of the future plight of reefs world-wide.

Please contact Emily Nicholson at e.nicholson@deakin.edu.au for any enquiries about this paper.

Citation:

Bland, L.M., Regan, T.J., Dinh, M.N., Ferrari, R., Keith, D.A., Lester, R., Mouillot, D., Murray, N.J., Nguyen, H.A. & Nicholson, E. (2017) Using multiple lines of evidence to assess the risk of ecosystem collapse. Proceedings of the Royal Society B: Biological Sciences, 284 [link]