Coral reefs are at risk of decline if global warming increases by 2°C

A study points out that an increase in global warming of 2°This could lead to the loss of cool areas in the sea called thermal refuges that protect coral reefs from rising temperatures.

Safe areas where corals can survive warming could disappear even if the Paris climate goals are met, a new study says. Image Credit: Copyright: wanzi989813 from Pixabay.

In a few areas, local ocean dynamics such as upwelling and strong currents were thought to mitigate the effects of warming seas, but scientists warn that these thermal refuges could shrink as the seas warm.

Coral reefs support the majority of marine biodiversity and around a billion people depend on them for their occupations and food security, says Adele Dixon, researcher at the Priestley International Center for Climate at the University of Leeds and lead author of the study. , published this month in PLOS Climate.

The study estimates the value of coral reef goods and services at US$2.7 trillion per year.

As we lack the resources to protect coral reefs everywhere, we have to decide which reef areas to protect. Our team decided to identify the areas least exposed to future climate change and the reefs that have the best chance of survival.

Adele Dixon, Study Lead Author and Researcher, Priestley International Center for Climate, University of Leeds

Dixon and the research team learned that about 85% of the world’s coral reefs are located in thermal refugia, but predict a decline of less than 1% if temperatures rise 1.5°C above levels. preindustrial.

While small portions of thermal refugia may exist, mostly in the Sumatra-Java region of the eastern Indian Ocean, the likelihood of total coral reef loss was high if temperatures increased by 2C, Dixon said.

Our research reinforces the stark reality that there is no safe limit of global warming for coral reefs. Following COP26 [climate summit] in Glasgow, where progress has been made towards the 1.5 degrees Celsius target, our finding shows that 1.5 degrees Celsius still represents substantial warming for ecosystems on the front lines of climate change.

Adele Dixon, Study Lead Author and Researcher, Priestley International Center for Climate, University of Leeds

She adds that the analysis emphasizes various effects in different regions. “At 1.5 degrees Celsius of warming, thermal refugia will disappear from all but 12 regions of the world: Polynesia and the Coral Triangle in the western Pacific Ocean. Refuges will be lost in areas like Oman, the Caribbean, Colombia and Indonesia.

At 1.5 degrees Celsius of warming, thermal refugia will disappear from all but 12 regions of the world: Polynesia and the Coral Triangle in the western Pacific Ocean. Refuges will be lost in areas like Oman, the Caribbean, Colombia and Indonesia.

Adele Dixon, Study Lead Author and Researcher, Priestley International Center for Climate, University of Leeds

Co-author and scientist at the Marine Physics and Geophysics Laboratory at James Cook University College of Science and Engineering, Australia, says Scott Heron, “Identifying the refuge locations linked to the greatest threat (heat stress causing coral bleaching and mortality) helps locate priority areas for management.”

Given that the rate at which corals have been ecologically affected has increased and is expected to accelerate, and that the number of people depending on coral reefs is increasing, suggests Scott Heron, “It is important to understand where disruptions related to climate change will occur. The large scale of the impacts underscores the urgent need for meaningful action on the causes of climate change”.

Oceanographer Mark Eakin says: “This study provides further support for the threat the climate crisis poses to coral reefs around the world. While many reefs have been immune to frequent and severe bleaching in the past, this study shows that even at the Paris Agreement’s most optimistic global warming level, very few of the world’s reefs will be spared. .

Tim McClanahan, a Wildlife Conservation Society senior ecologist involved in coral reef conservation, working in Mombasa, Kenya, recounts SciDev.Net that the study reveals that there will be few reefs that experience low chronic stress in the future.

“Chronic stress will become widespread and corals will have to resist or adapt to chronic stress to survive. Future chronic stress sanctuaries will therefore be less common,” McClanahan said.

He is convinced that sanctuaries that resist or recover from chronic stress will always exist. There will be coral reef sanctuaries but fewer that avoid prolonged heat exposure.

“Therefore, there is a need to assess where the resilient and recovering sanctuaries are to reduce the number of additional threats these reefs face, such as fishing and pollution,” he adds.

One topic that isn’t well covered in the study, McClanahan says, is the wide variations in corals’ sensitivity to heat stress.

The corals of the Coral Triangle, for example, are less sensitive to stress than those of the Indian Ocean and the Caribbean… Some reefs are frequently exposed to stress and the corals have adapted to it while others are not. and therefore not suitable.

Tim McClanahan, Senior Ecologist, Wildlife Conservation Society

Journal reference:

Dixon, AM, et al. (2022) Future loss of local-scale thermal refugia in coral reef ecosystems. PLOS Climate. doi.org/10.1371/journal.pclm.0000004.

Source: https://www.scidev.net

Teresa H. Sadler