“The deep ocean is warming slower than the surface but dramatic changes are ahead,” according to Mr. Isaac Brito-Morales (University of Queensland), lead author of the new paper “Climate velocity reveals increasing exposure of deep-ocean biodiversity to future warming” published in Nature Climate Change on 25 May 2020 under the DOI: 10.1038/s41558-020-0773-5. Their study reveals that the deep ocean faces rapidly accelerating threats from global warming by 2100, irrespective of the greenhouse gas (GHG) pathway society follows.
To look at how ocean life was responding to climate change, they used a metric known as climate velocity which determines the probable shift in the speed and direction of a certain species as the ocean gets warmer. It was calculated throughout the ocean for the past 50 years and then for the rest of this century using data from 11 climate models. Results showed that climate velocity is currently faster at the surface than in deeper water, and will remain so, unless there’s rapid reduction of emissions.
“However by the end of the century, assuming we have a high-emissions future, there is not only much greater surface warming, but also this warmth will penetrate deeper,” Mr. Brito-Morales said. “No matter what emissions scenario we follow, this threat to deep ocean biodiversity remains, so we need to plan conservation actions to ameliorate non-climate threats ,” he added. ”
The findings has an interesting twist though, researchers discovered that climate velocity is not only moving at different speeds at different depths in the ocean, but also in different directions which will greatly affect the design of protected areas required. Now that it has become known that deep-sea biodiversity will not be spared from climate change impacts, its critical that we start planning for deep-sea MPAs.
For this study, team members of AquaMaps Project (www.aquamaps.org) –Ms. Kathleen Reyes (Q-quatics), Ms. Cristina Garilao (GEOMAR) and Ms. Kristin Kaschner (Albert‐Ludwigs University) provided global distribution maps for over 33,000 marine species.
Abstract: Slower warming in the deep ocean encourages a perception that its biodiversity is less exposed to climate change than that of surface waters. We challenge this notion by analyzing climate velocity, which provides expectations for species’ range shifts. We find that contemporary (1955–2005) climate velocities are faster in the deep ocean than at the surface. Moreover, projected climate velocities in the future (2050–2100) are faster for all depth layers, except at the surface, under the most aggressive GHG mitigation pathway considered (representative concentration pathway, RCP 2.6). This suggests that while mitigation could limit climate change threats for surface biodiversity, deep-ocean biodiversity faces an unavoidable escalation in climate velocities, most prominently in the mesopelagic (200–1,000 m). To optimize opportunities for climate adaptation among deep-ocean communities, future open-ocean protected areas must be designed to retain species moving at different speeds at different depths under climate change while managing non-climate threats, such as fishing and mining.
The study [authors] in the news:
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