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Risk index could help save vulnerable marine species from climate change

The study shows almost all marine life is already at risk, particularly species like sharks and pufferfish, especially if we cannot find a way to start mitigating risks now.

 (CN) —The impact of climate change on land can be felt viscerally now seemingly every day, especially in this heat record-breaking summer. Within our oceans, the effects are somewhat tempered, with rising temperatures and increased levels of carbon dioxide taking much longer to affect ocean systems than on land. However, this doesn’t mean that aquatic life isn’t threatened.

Researchers with Dalhousie University in Canada presented an index that evaluates the risk posed to marine species by climate changes, with the hope that the index will help resolve marine conservation and management strategies.

The analysis of nearly 25,000 marine species, which includes from animals and plants all the way down to protozoans and bacteria, is rooted in the need for creating a system that can help focus conservation efforts of the most threatened species.

“We looked at 12 aspects that measure the impacts of climate change on each species. These twelve impacts fall under three categories: the present-day sensitivity to climate change, the innate adaptivity of each species, and the future exposure to climate change,” said Derek Tittensor, co-author of the paper and professor of biology and Jarislowsky Chair in marine ecosystem forecasting at Dalhousie University.

The index integrates and evaluates these impacts across geographical differences, modelling a more comprehensive framework that can provide realistic, actionable data on which species and regions should be prioritized. The study also takes human and socio-economic factors into account.

According to the study published Monday in the journal Nature, an average of 85% of marine life will be under high or critical risk by 2100, under a high greenhouse gas emissions scenario. In contrast, the study also runs a scenario where climate effects have been mitigated, resulting in almost all marine species becoming less vulnerable, with only half remaining in high or critical risk.

For establishing conservation efforts, researchers modelled the metrics of climate risk, extinction risk and initial biodiversity and endemism against each other. Models indicated that the combination of these risk factors intersect most significantly in regions near Southeast Asia and Oceania, but the intersection of these metrics extended across a tenth of the oceans as a whole.

Species that make their habitat in these tropical ecosystems or near shorelines showed higher risk in all scenarios.

“The recurring high climate risk of nearshore ecosystems is notable, as they have also been identified as high-priority areas for biodiversity conservation and food provision and are disproportionately subjected to non-climatic stressors,” the study stated.

These non-climactic stressors are some of what differentiates high and critical risk species from the lower risk species. The study also found that larger predator animals, like sharks, are most vulnerable to ecosystem restructuring, and are in the most danger under high emission scenarios. Sharks and tunas, for example, are uniquely vulnerable to human impact from fishing, and their size and geographic range contribute to even more risk.

Human impact, beyond the contribution of greenhouse gases in the environment in the first place, play a large role in marine risk. Socio-economic factors can exacerbate the risk even further. Compared to countries that do not rely so heavily on our oceans, nations that rely upon fishing for both food resources and trade are likely to experience disproportionate negative effects as many of them also happen to also be in those regions with established climate vulnerability.

The study explained, “low-income countries, which tend to have lower levels of wealth and food security and a higher dependency on fisheries, and which contribute the least to global CO2 emissions, have systematically higher climate risks to their fisheries under the high-emission scenario but also experience the greatest risk reduction through mitigation.”

Researchers established the climate index as a tool to help prioritize high risk species and ecosystems and use the high mitigation scenario modelled by the study to represent a hopeful future where climate change relief strategies are developed and adopted globally.

“We have a follow-up study in review that looks at operationalizing this work at a much finer scale, to demonstrate how it can be applied in a more regional context as opposed to the global ‘big picture’.” said Tittensor in an email interview.

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