How climate change is wreaking havoc on the coral ecosystem worth $375bn annually

Featured article by Deborah Brosnan, a climate scientist on building local resilience for global impact

The year 2023 was a terrible one for the oceans. But new data show that February 2024 saw a new and unsettling low point for the ocean: average global sea surfaces climbed to the hottest temperatures ever recorded in any month since at least 1979, according to the Copernicus Climate Change Service. 

Fuelled by El Niño patterns and climate-change-induced marine heatwaves, these ocean temperatures are now pushing the world towards its fourth mass coral-bleaching event, the National Oceanic and Atmospheric Administration announced on March 5th—with the world’s largest coral-reef ecosystem, Australia’s Great Barrier Reef, among the areas hardest hit.

Coral reefs are a vital natural ecosystem, impacting every aspect of community climate resilience and marine life. Living coral reduces over 95% of a wave’s energy, reduces storm surge and keeps sand on our beaches. Corals enhance biodiversity—supporting 25% of marine biodiversity and key fisheries.

Besides the inarguable environmental impacts, the ecosystem resources and services that coral reefs provide are worth $375bn per year. It is estimated that the avoided coastal flooding costs from corals in the US alone amount to $1.8bn. Coral brings in $36bn in tourism revenues globally. The ocean economy—which worldwide employs 350m people and is worth up to $6trn annually—is largely reliant on the marine life that lives within reefs.

As corals collapse before our eyes, what can be done?

Scientists have been raising the alarm about corals and ocean warming for years, with some estimating that the planet has lost half of its coral reefs since the 1950s. These scientists’ climate models and field research show corals at continued and increasing high risk from marine heatwaves. 

Local tactics for coral recovery will be key to reducing the impacts of marine heatwaves and increasing coral-survival rates. 

What we are doing with OceanShot in the Caribbean, for instance, prioritises coral and reef-ecosystem rebuilding. As part of that programme, our dedicated team has diligently established and maintained coral nurseries and built reefs that support outplanted corals. While we avoided the worst coral bleaching and mortality from the 2023 ocean heatwave, our programme did experience damage. With temperatures returning to normal, we are taking stock of the damage. We continue to ask ourselves if there is anything we can do to help the surviving corals fully recover and prevent additional death in the future.

Insurance schemes that look to protect nature are starting to gain traction. In 2022, The Nature Conservancy (TNC) was instrumental in creating one of the first, insuring coral reefs in Hawaii against storms of a certain category. The insurance payout would support clean up and reef restoration.  TNC has since enhanced this program, and insurance companies like Munich Re and the insurance brokerage firm Willis Towers Watson have been leaders in this approach. The idea is spreading to other parts of the world including reefs in Fiji and Mexico.

Common coral killers

To help corals recover, we can today start to better control seaweeds and maintain good water quality. Algae have a big impact on the health of corals: longer-term survival of corals is highly dependent on whether a reef is covered with large macroalgae or whether algal cover is low. The more seaweed, the worse the prognosis for corals. Seaweeds can do a lot of harm to corals in many ways, outcompeting them for space, smothering them, causing local anoxia over corals, and more.

Never doubt the power of citizen science

Back in 2021, anticipating—no doubt, fearing—that we would see an ocean-warming event like 2023, Mary Donavan and a team of international scientists investigated what factors affect bleaching and post-bleaching coral recovery associated with rising ocean temperatures. Today known as Reef Check, these scientists carefully analysed a plethora of factors across 223 sites spread over the Caribbean and the Indo-Pacific. This data set of studies was carried out by roughly 10,000 volunteer scientists and citizen scientists. Mobilising a tribe of citizen scientists can help in data collection and bolstering coral stewardship. PADI AWARE is another example of recruiting citizen science. 

With some scientists predicting that 2024 will be at least as bad for the oceans as 2023 was, starting to prepare now can safeguard a vital ecosystem and the human lives and global economies reliant on it. We must do all we can to address global climate change, but time and again we learn that each of us in our own communities has the power to change the outcome. Act locally as you think globally.

Author Deborah Brosnan, president and founder of Deborah Brosnan & Associates, May 10, 2024