Coral reefs are an important part of a healthy global ecosystem. They function as nurseries for many fish and provide important coastal protection for low-lying islands.

An estimated 400 million people in developing countries depend on coral reefs for protection and income. According to a report by Deloitte Access Economics, tourism at the Great Barrier Reef alone is a $6.4 billion a year industry, providing 64,000 jobs.

But the future of our coral reefs is at risk. Back-to-back coral bleaching events caused by a warming climate are jeopardising their survival.

Marine biologist Professor Terry Hughes has dedicated his career to studying coral reefs. I recently had the chance to talk to him about his research on the linkages between coral reef ecosystems, the goods and services they provide to people and the role of governance.

The poster child of climate change

“In the context of climate change, coral reefs are often called the canary in the coalmine,” says Terry. “ I am not sure if this analogy is accurate or that coral reefs are more vulnerable than other ecosystems.”

Professor Terry Hughes
Professor Terry Hughes

“In Australia, we are currently dealing with burning rainforests, so one could argue that many other ecosystems are equally at risk. But coral reefs are very photogenic and iconic, so with their increasing degradation, they have become the poster child for the impact of climate change on biodiversity.”

The other issue with the canary metaphor is that it suggests that we’re still in the early stages of understanding and responding to the impact of climate change on the natural environment.

“This is misleading because it implies that it’s an issue that may occur in the future,” says Terry. “But coral bleaching is happening right now and we can’t afford to delay action any longer.”

What is coral bleaching?

In simple terms, coral bleaching is a visual indicator for warming oceans. When water temperature rises, it disrupts the symbiotic relationship between corals and zooxanthellae (the algaes that live inside and provide essential nutrients to corals).

Zooxanthellae under heat stress release toxins and therefore get kicked out by their coral hosts. Without these plant pigments, the calcium carbonate skeleton of the corals becomes visible, giving them a white – or bleached – appearance.

Bleached tabular corals
Bleached tabular corals during the 2017 coral bleaching event at Mission Beach, Northern Great Barrier Reef. Image credit: Bette Willis

Corals can recover from bleaching events, but only if the water temperature drops again relatively quickly. If the water temperature stays too high for too long, corals will die off and eventually become covered in a different types of algae, throwing a delicate ecosystem off balance.

Coral bleaching events have intensified in reach and frequency

Coral researchers have been witnessing coral bleaching events since the 1980s. Since then these bleaching events have intensified in both frequency and reach.

The summer of 1997/98 was one of the hottest on record in Australia. That year, 74% of inshore and 21% of offshore reefs at the Great Barrier Reef were showing moderate to high levels of bleaching. 1998 was also the year of the first global coral bleaching event, meaning that reefs everywhere were affected.

In the summer of 2016, sea temperatures in Australia reached the highest ever recorded. And in 2017 they got hotter again, causing the longest lasting and most severe global bleaching event ever recorded.

“Bleaching is very selective. Some species bleach and die, while others recover. In 2017 some of the tougher ones died,” explains Terry. “We [the scientists community] only expected this sort of consecutive bleaching to happen in 20 years time.”

While the Paris Agreement states that nations will be working to keep global warming below 2 degrees in this century, recent reports show that the average global temperature is already 1 degree above pre-industrial times.

“It’s now looking more and more likely that we’re going to reach 2 degrees – and much sooner than anticipated,” says Terry. “If the average global temperature increases by 3 or even 4 degrees, the impact is going to be severe not just for our coral reefs but the whole global ecosystem.”

A crisis of governance

“There’s no doubt that our current coral reef crisis is a crisis of governance,” states the scientist. “Australia needs to take much more urgent action toward reducing greenhouse gas emissions that are causing global warming. “

“We currently have all sorts of policies on fishing and water pollution that are aimed at protecting our reef. But none of this is going to help if we don’t move away from our reliance on fossil fuel. One tactic by government is to keep pushing the responsibility on the individual and focussing on trivial things like banning straws and sunscreen. These things are admirable, but should never be seen as a replacement for governance.”

While Terry has noticed some shift in the mindset of politicians, this appeared to happen on the state rather than the federal level which is supporting the Adani coal mine and is putting pressure on state governments to lift their ban on onshore gas exploration projects.

Reef fish and coral bleaching
Reef fish that do not directly depend on live corals are still around – but how long before the dead skeletons erode and deprive them of their habitat? No Name reef (Lizard Island region), October 2016. Image credit: Greg Torda

At the same time, the Australian government uses a loophole to “carry over” carbon credits from the Kyoto protocol to meet its Paris agreement targets.

And even though Terry is seeing the beginnings of governance at a global scale, there’s still a lot of work to be done. “The issue with action on climate change is that we’re dealing with a complex set of competing agendas,” he says. “The fossil fuel industry is incredibly powerful and ultimately we’re talking about completely revolutionising the world’s economies.”

New technologies and reasons for hope

Despite the challenges in achieving consensus on the government level, Terry has reasons for hope. “A lot of decision-making about investments isn’t made on the federal level and ultimately people vote with their feet,” he says.

“Australia leads the world in residential solar uptake and the adoption of renewable power sources is transforming the energy grid.”

Coral Bleaching Survey Orpheus Island 2017
Coral Bleaching Survey Orpheus Island 2017 – Image credit: Greg Torda

What’s more, public awareness about climate change is at an all-time high. And Terry hopes that this focus on climate change is also going to lead to better governance. He’s a big supporter of the School Strike for Climate and believes that the attention the younger generation is bringing to the topic can be a big driver for change.

“Your children are going to have to bear the brunt of our inaction on climate change. If you really want to make a difference for their future and the future of our planet, vote for parties that make action on climate change a priority and get involved in public discourse.”

Follow Terry Hughes

Terry Hughes regularly publishes articles about research on the Great Barrier Reef – and coral reefs more generally – on the The Conversation. He is also an avid contributor to the climate change discussion on Twitter.

Hero image credit:  Yanguang Lan on Unsplash

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