The scientists rebuilding our coral reefs after El Niño

Explaining what an El Niño is and why it happens is a complicated business and, right now, as we stare down the barrel of what the media is describing as a ‘Super El Niño’ or even a ‘Godzilla El Niño’, we must begin with one irrevocable truth.

“El Niño shows how closely the ocean and atmosphere are connected,” states Devon Ledbetter, former Canon Fellow and a Senior Research Associate and Program Manager at the University of Miami Rosenstiel School’s Rescue a Reef. “When trade winds across the tropical Pacific weaken, warm surface water shifts eastward, setting off changes in atmospheric circulation that can affect rainfall, agriculture and hurricane activity far beyond the Pacific.”

The trade winds (a name which dates back to the era of sailing ships that needed reliable winds to enable trade between Europe and Asia) usually blow from east to west, close to the equator, and this has some really important functions for global ecology. For example, when the wind drags surface waters to the west, they are replaced by colder, nutrient-rich water from deep in ocean, which feeds plankton. And the plankton are, of course, food for fish and birds. The movement of this warm water to Asia and Australia also creates warm, moist air, which rises and becomes necessary rainfall. Equally, the cool water that remains means that the air stays calm in the Americas, preventing flooding and storms.

In an El Niño, these winds weaken or even reverse. So, the warm water doesn’t go to where it’s needed. Instead, the heat and moisture releases into the atmosphere, changing air currents and the way that weather systems move around the world. The consequences, as we know, can be devastating and were witnessed by those on the front line of coral reef conservation and restoration during the El Niños of 2016, 2019 and 2024 – which, you’ll note, are troublingly close together. And data tracking back as far as January 2026 is painting a picture of the expected El Niño as more powerful and with far greater consequences than any seen in living memory.

“The models suggest it's going to be more severe than anything that's come before, which is obviously fairly terrifying,” says Dr Jamie Craggs of Coral Spawning International. He is a regular visitor to reefs around the world, working with organisations and NGOs on restoration programmes (such as his partnership with Canon and Nature Seychelles) and has seen first-hand the impact of a rapid succession of El Niño events. Coral is incredibly sensitive to water temperature, so even a single degree rise, sustained over a period of time (known as ‘degree heating weeks’) can trigger a massive bleaching event. However, he says, “not all corals are equal. Some will bleach, but it’s key to understand that bleaching is a natural phenomenon and corals can bleach and recover. It's the recovery that we're interested in.”

And so, while bleaching is a fact of life, finding solutions to the increasingly short recovery times between events is now priority number one. “Historically, there was around ten to twelve years in between these events and now there's less time,” he adds. At the coalface of this is Dr Luca Saponari, Senior Science & Technical Field Officer at Nature Seychelles. “In Seychelles, temperature naturally fluctuates and most of the corals are already resistant to this,” he explains. “High water temperature, pollution, overfishing or increased anchorage can put a stress on them, but if this is short-term, they can sustain and recover”.

However, he explains that the impact of an El Niño exposes corals to higher temperature for far longer, breaking their symbiotic relationship with the algae (zooxanthellae) that live inside their tissue and provide the majority of their energy. Corals – and this may come as a surprise – are predators and actively catch and feed on plankton, but this is not enough to support their survival. So, prolonged high temperatures will reduce the energy supply. “Basically, they are starving, “says Dr Saponari. “And this can only be sustained for a short amount of time.”

A drastic loss of coral cover caused by an El Niño also gives space for other kinds of algae to grow, which further reduces the chances of reef recovery. “Because algae compete for space and light, and they grow faster than corals,” he explains. “They can also touch the corals and damage their tissue, causing disease and mortality. They also create a kind of barrier against larvae – new corals – so they can’t settle on the reef.”

So, as Devon says, everything is interconnected and bleaching is only the first in a very serious chain of events. A loss of reefs hits fishing and fisheries, affecting the job market and driving up global food prices, plus their protective qualities as wave barriers leave coastal communities at huge risk from flooding and erosion. Then there are the lesser-known impacts. Dozens of marine-derived treatments already in the world – from cancer-fighting medicines to antivirals, painkillers and anti-inflammatories – would never have seen the light of day had it not been for our global reef systems.

So, what are reef managers and conservationists doing now to mitigate the impact of this incoming Super El Niño? “There is little we can do to protect them from the climatological impacts,” says Devon, whose team put a plan in place as soon as the World Meteorological Organization raised the alarm. “But we do have safeguards to ensure that our stock is protected, so we can maintain genetic diversity amongst our corals and not lose entire genotypes – protecting the cream of the crop, essentially.” This saw them move growing corals from shallow water into deep water nurseries to keep them cooler, while some were taken out of the sea entirely and into land-based facilities.

This strategy somewhat mirrors that of Nature Seychelles, where Dr Saponari and his team at ARC – a land-based coral aquaculture facility – are also focused on protecting the coral genotypes. “We try to work with thermal resilient corals; those that are naturally better at resisting the increase of temperature,” he explains. “And we integrate these into the spawning programme we’re collaborating on with Coral Spawning International and Canon. This is vital because it allows us to increase the genetic diversity of corals and create a new generation that can withstand the warmer ocean of the future. This is the most important tool that we have to reduce the impact of El Niños and bleaching in general.”

And while active work is happening near-constantly on reefs around the world, like Dr Saponari, Dr Craggs is taking a long-term view of how the world’s reefs will need to adapt to meet the new realities of a warmer, less predictable climate. And this includes using bleaching events as an opportunity to understand where restoration should be going in the future. “Because, however good your lab-based experiments are, there are so many confounding factors on the reef that you just can't replicate,” he explains. “Natural bleaching lets us see which species are more resilient, but also what the variability is within the population – then we can identify those that are strongest, which is particularly important when we start to think about selective breeding and creating stronger offspring.”

The big picture, of course, makes for bleak reading, but there are tiny pockets of hope. The Global Coral Reef Monitoring Network has been issuing reports for forty years, updating the world on the status of the world’s reefs, based on of survey data. “The latest reports obviously show a slow, stepwise reduction in coral coverage, but it also highlights the ability of reefs to recover following impact,” Dr Craggs says. “But it cannot be assumed that what worked in restoration ten years ago will work in the future. We’ll need to evolve our approach and create the tools to adapt to a future ocean and climate.”

Follow the progress of our work with Coral Spawning International and Nature Seychelles here on VIEW.