Corals doomed even if global climate goals met, according to study

  • Most of the world’s coral reefs will not survive even if global warming is capped within Paris climate goals
  • Losing the coral reefs will have devastating consequences on marine ecosystems, and social and economic impacts on those who depend on them for their livelihoods
Agence France-Presse |

Latest Articles

SOTY 2022-23: Performing Artist first runner-up uses dance to convey powerful stories

Move over Met Gala: Mutt Gala’s dog art auction to help UK rescue charity

Join us and revel in the fun ‘In The Common Room’ on RTHK Radio 3

US White House holiday decor features likeness to Biden family pets

Paediatric leukaemia cases rise in Brazil, linked to soy production

Scientists say no reefs will be spared the impact of climate change at 2 degrees Celsius of global warming. Photo: Shutterstock

Coral reefs that anchor a quarter of marine wildlife and the livelihoods of more than half-a-billion people will most likely be wiped out even if global warming is capped within Paris climate goals, researchers said Tuesday.

An average increase of 1.5 degrees Celsius above pre-industrial levels would see more than 99 per cent of the world’s coral reefs unable to recover from ever more frequent marine heatwaves, they reported in the journal PLOS Climate.

At two degrees of warming, mortality will be 100 per cent according to the study, which used a new generation of climate models with an unprecedented resolution of one square kilometre.

Experts say there’s no turning back on climate change now

“The stark reality is that there is no safe limit of global warming for coral reefs,” lead author Adele Dixon, a researcher at the University of Leeds’ School of Biology, told Agence France-Presse.

“1.5C is still too much warming for the ecosystems on the frontline of climate change.”

The 2015 Paris Agreement enjoins nearly 200 nations to keep global heating “well below” 2C.

Australia’s Great Barrier Reef, the world’s largest reef system, has lost more than half of its colourful corals due to climate change. Photo: Shutterstock

But with more deadly storms, floods, heatwaves and droughts after only 1.1C of warming to date, the world has embraced the treaty’s more ambitious aspirational goal of a 1.5C limit.

A landmark report in August by the UN’s IPCC climate science panel said global temperatures could hit the 1.5C threshold as soon as 2030.

In 2018, the IPCC predicted that 70 to 90 per cent of corals would be lost at the 1.5C threshold, and 99 per cent if temperatures rose another half-a-degree.

Climate change could cause 216 million people to migrate, World Bank warns

The new findings suggest those grim forecasts were in fact unduly optimistic.

“Our work shows that corals worldwide will be even more at risk from climate change than we thought,” Dixon said.

The problem is marine heatwaves and the time it takes for living coral to recover from them, a healing period known as “thermal refugia”.

When corals are under stress, they expel the algae in their tissues. Graphic: Doris Wai

Coral communities usually need at least 10 years to bounce back, and that is assuming “all other factors” – no pollution or dynamite fishing, for example – “are optimal”, said co-author Maria Berger, also at Leeds.

But increased warming is reducing the length of thermal refugia beyond the ability of corals to adapt.

“We project that more than 99 per cent of coral reefs will be exposed at 1.5C to intolerable thermal stress, and 100 per cent of coral reefs at 2C,” Berger told Agence France-Presse.

COP26 just ‘greenwashing’, say climate activists like Greta Thunberg

Australia’s Great Barrier Reef, the largest coral system in the world, has seen five mass bleaching events in the last 25 years.

An unpublished study obtained by Agence France-Presse, written by experts at the US National Oceanic and Atmospheric Administration’s Coral Reef Watch unit, says the Great Barrier Reef was in the grips of a record-breaking heat spell yet again in November and December.

Oceans absorb about 93 per cent of the excess heat from greenhouse gas emissions, shielding land surfaces but generating huge, long-lasting marine heatwaves that are already pushing many species of corals past their limits of tolerance.

The Great Barrier Reef has experienced five mass bleaching events – 1998, 2002, 2016, 2017 and 2020 – all caused by rising ocean temperatures driven by global heating. Photo: Shutterstock

A single so-called bleaching event in 1998 caused by warming waters wiped out eight per cent of all corals.

Coral reefs cover only a tiny fraction – 0.2 per cent – of the ocean floor, but they are home to at least a quarter of all marine animals and plants.

Besides supporting marine ecosystems, they also provide protein, jobs and protection from storms and shoreline erosion for hundreds of millions of people worldwide.

Hong Kong teen climate activists on striking every week, asking city’s McDonald’s for vegan burger

The value of goods and services from coral reefs is about US$2.7 trillion per year, including US$36 billion in tourism, the report said.

Global warming, with the help of pollution, wiped out 14 per cent of the world’s coral reefs from 2009 to 2018, leaving graveyards of bleached skeletons where vibrant ecosystems once thrived, recent research has shown.

Loss of coral during that period varied by region, ranging from five per cent in East Asia to 95 per cent in the eastern tropical Pacific.

Sign up for the YP Teachers Newsletter
Get updates for teachers sent directly to your inbox
By registering, you agree to our T&C and Privacy Policy