During summer 2017 a large swath of Australia’s Great Barrier Reef—normally a riot of electric oranges, reds and other colors—turned ghostly pale.

Unusually warm water temperatures, partly due to global warming, had caused the corals to expel from their tissues the symbiotic algae that provide them with food and give them their brilliant hues. It was the second mass-bleaching event to hit the reef in as many years. Together, the back-to-back events hit two thirds of the reef.

Now, with the 2019 Australian summer poised to begin, atmospheric scientists are predicting an El Niño—a recurring period marked by warmer temperatures in the tropical Pacific Ocean. This potential for high temperatures again poses a threat to the Great Barrier Reef, one that marine biologist Terry Hughes—a high-profile champion of coral reef protection—will be watching, looking for signs of more damage to the reef as he continues to push for protecting it.

Hughes thinks there are some worthy mitigation efforts to explore, such as reforesting the watersheds that drain into the reef to prevent pollution-bearing runoff. But ultimately he believes the key to saving corals lies in addressing greenhouse gas emissions that fuel global warming.

Professor Terry Hughes. Credit: Arccoe Wikimedia

Hughes’s efforts to raise awareness about the fate of the 2,300-kilometer-long coral reef—the largest on the planet and home to thousands of marine species—have put him at odds with business and political interests. Last month it emerged the Australian Research Council (ARC) would drop its funding of the coral reef institute Hughes directs at James Cook University in Queensland—a move decried by ocean scientists around the world. (The ARC and the current conservative Australian government have said the decision was not politically motivated, according to news reports.) Last week Hughes was awarded The John Maddox Prize for championing scientific evidence in the face of hostility. Scientific American caught up with him at the annual Falling Walls science conference in Berlin earlier this month and spoke about the future of the Great Barrier Reef.

[An edited transcript of the interview follows.]

What is your outlook for the Great Barrier Reef in the coming months?

NOAA [the U.S. National Oceanic and Atmospheric Administration] and the Australian Bureau of Meteorology are both projecting a high likelihood of an El Niño event forming later this year. If that happens, the likelihood of bleaching when summer sea temperatures peak next March would be very high, but we won’t know for sure until about January. A well-timed cyclone could cool the water despite the long-term forecast. But you have to be careful what you wish for. In 2016 the southern third of the Great Barrier Reef was rescued by a spent cyclone that brought the [water] temperature down about 2 to 3 degrees Celsius. But with Cyclone Debbie in 2017, the bleaching had already occurred and the storm was a category 4 when it hit the coast—so it was actually very damaging and destructive [to the reef].

How do you monitor a bleaching event?

Our aerial surveys, which we match to satellite temperature data, are reef-wide. It takes us seven or eight days to crisscross the entire Great Barrier Reef in a small plane flying up to eight hours a day. It’s pretty grueling but that’s the best way that we have of getting the full picture. We ground-truth all of that [data] underwater [during dives]. Each event that we study has a different geography. The 2016 event was very much a northern affair. The maps for the 2017 bleaching will show that the hottest part of the reef—the part that had the most bleaching—was in the center.

Dead coral. Credit: J.W. Alker Getty Images

Is there any area of the reef you are especially worried about?

My worst nightmare is that the bottom [southern] third of the Great Barrier Reef, which escaped the last two events, will bleach. It was simply good luck that prevented it from bleaching in 2016 and 2017. Those reefs have very high numbers of branching corals that happen to be the most susceptible to bleaching. So if it does get a blast of heat next summer or some summer soon, there will be high levels of mortality. That would mean all sectors of the reef will have been hit within a handful of years.

How did the Australian government respond to the bleaching events?

The Great Barrier Reef story in Australia, following the unprecedented back-to-back bleaching, is very politically contentious. You would think an appropriate response by the government would be to declare, for instance, that it wasn’t going to proceed with the world’s largest coal mine [with a coal shipping terminal near the reef] or that it would ramp up its renewable energy targets. Neither has occurred. The government has put quite a lot of money into investigating different interventions. Some are downright silly—the [underwater cooling] fans, the floating sunscreen. There’s a campaign to ban plastic straws. If you were cynical, you would say that it was more about giving the appearance of helping reefs when the elephant in the room is still climate change. There’s also money for improving water quality. Runoff of sediment and nutrients from agriculture into the inner part of the Great Barrier Reef is an important issue, but the amount of funding that’s being spent on that is nowhere near sufficient to reach the government’s own targets. As the country responsible for the Great Barrier Reef World Heritage Area, Australia should be leading the international efforts to reduce emissions, especially following the latest IPCC [Intergovernmental Panel on Climate Change] report. Our current commonwealth government has officially signed on to the 1.5-degree C target [for limiting global temperature rise] of the Paris agreement, but Australia’s emissions are actually increasing.

How will the loss of funding from the Australian Research Council affect your work?

It’s roughly a quarter of our funding and it won’t take effect for another two to three years, so we’ve got time to continue with our current level of activity and to change our funding model by moderate amounts to make up that loss. It’s not good news, certainly. But we will continue to do the research that we’re doing, especially if we see bleaching next year.

What do people misunderstand about the Great Barrier Reef?

There are still about 10 billion corals out there alive and kicking. We’ve just gone through one hell of a natural selection event where the so-called losers—the heat-susceptible species—have been badly depleted. The mix of species has changed. The genetic composition of the coral populations is changing. I think that is just the beginning of a transition that hopefully will make the Great Barrier Reef tougher for inevitable future events. Things will generally get worse before they get better. Until CO2 emissions and temperatures stabilize, the corals are going to be in for a rough ride. Because corals have big populations that are geographically widely dispersed, there is light at the end of the tunnel—but it is completely contingent on whether we can keep temperatures to the 1.5-degree C target.