Friday, February 12, 2010

Assessing the vulnerability of sharks and stingrays to climate change

Scientists have developed an innovative model for predicting the vulnerability of multiple species in a geographic area to climate change. Andrew Chin and fellow researchers tested the model on sharks and stingrays in the Great Barrier Reef though the approach really is applicable to a wide range of ecosystems.

The study published in the journal Global Change Biology identified 30 of 133 species as either moderately or highly vulnerable to climate change with the most vulnerable species including the freshwater whipray,porcupine ray, speartooth shark, and sawfishes. It found that freshwater/estuarine and reef associated sharks and rays are most vulnerable to climate change.

Their method is a qualitative approach which uses published data and expert opinion to rank species vulnerability as either low, moderate, or high within a number of categories including species rarity, habitat specificity, physical-chemical intolerance, mobility, etc. For a given species, the vulnerability has to be high in all categories to receive an overall ranking of "highly vulnerable."

The approach is innovative for a number of reasons. While many studies have evaluated species vulnerability, this is one of the few to assess numerous species across an ecosystem taking into account multiple factors including temperature, ocean acidification, sea level rise, severe weather, etc. The method also is able to incorporate uncertainty. Adhering to the precautionary principle used in fisheries, if information was not known to assign a ranking for a category, the investigators would give the rank of "high."

One of the advantages of the methodology is that as more information becomes available over time, it can be incorporated into the model to update the ranking. Another advantage is that the relatively simple qualitative approach gives the model a transparency and makes it open to being developed and reviewed with input from a wide variety of stakeholders.

Of course there are some drawbacks as well. By taking a look at such a large number of species over a relatively big geographic area, the study has to make assumptions that may not hold. For example, the model assumes that all the factors of climate change and components of vulnerability have equal importance with respect to sharks and sting rays, when in fact some might be more significant than others.

The study also does not take into account synergistic effects that might arise from climate change and other human disturbances such as fishing or coastal development. For this reason, the researchers warn that the impacts to certain species might be somewhat worse than that predicted by the model.

--Reviewed by Rob Goldstein

CHIN, A., KYNE, P., WALKER, T., & McAULEY, R. (2010). An integrated risk assessment for climate change: analysing the vulnerability of sharks and rays on Australia's Great Barrier Reef Global Change BiologyDOI: 10.1111/j.1365-2486.2009.02128.x

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