Inside the South London Lab Helping to Save the World’s Coral Reefs

London is miles from the sea and even further from the warm, bright waters where tropical coral reefs usually belong. It is a city of buses, basement flats, foxes, fried chicken shops, commuter rain and the Thames moving brownly under bridges. Not, on the face of it, an obvious place to help save a reef.

And yet, in Forest Hill, South London, the Horniman Museum and Gardens is playing a small but significant part in one of the great conservation challenges of our age: the survival of the world’s coral reefs.

The work is called Project Coral, and it sounds faintly improbable until you understand what is happening. In a controlled laboratory behind the scenes at the Horniman Aquarium, scientists have learned how to persuade coral to spawn in captivity. Not by lucky accident. Not once, as a strange aquatic fluke. But predictably, under carefully managed conditions.

Coral reproduction is one of nature’s more spectacular acts of timing. Many corals reproduce by releasing eggs and sperm into the water during mass spawning events, triggered by a precise combination of seasonal change, water temperature, daylight and moonlight. In the wild, this may happen on only one or two nights a year. For scientists trying to study coral reproduction, that is both beautiful and maddening. Nature opens the door for a few hours, usually at night, then shuts it again for another year.

Project Coral was established to solve that problem. Led by Dr Jamie Craggs, Principal Aquarium Curator at the Horniman, the team has developed techniques for recreating the environmental signals that tell coral it is time to spawn. Temperature, light, day length and artificial lunar cycles are all carefully controlled. In effect, the lab teaches coral what season it is.

It is a strangely poetic piece of science: a small artificial reef-clock ticking away in SE23.

The results have been important. The Horniman’s methods have helped make coral spawning in aquariums planned and predictable, rather than something researchers simply hope might happen. That allows scientists to produce coral larvae, study their survival, examine genetic diversity and investigate which corals might be better able to withstand warming seas.

This is not just about keeping pretty coral alive in glass tanks. Coral reefs support a huge range of marine life, protect coastlines, sustain fisheries and attract tourism. They are often called the rainforests of the sea, which is one of those phrases that has become familiar because it is useful and largely true. But reefs are under severe pressure from rising sea temperatures, bleaching events, pollution, ocean acidification and physical damage. Around the world, underwater cities are turning pale.

Sexual reproduction is one way coral populations create genetic diversity, and genetic diversity is essential if reefs are to have any chance of adapting to changing conditions. If researchers can reliably breed corals in laboratory conditions, they can better understand how young corals develop, which combinations are most resilient, and how restoration projects might be improved.

The Horniman’s Project Coral lab now studies corals from several geographical regions, including Australia, Fiji, the Indian Ocean, Singapore and the UK. This gives scientists the chance to compare corals from different places in one controlled setting. Current and recent research has included cross-fertilisation between geographic groups, coral fluorescence, Pink Sea Fan spawning and work involving juvenile sea urchins.

The sea urchin detail is particularly pleasing. In one strand of research, young sea urchins were used to graze algae around baby corals, improving their chances of survival. Tiny marine gardeners, in other words, trimming the nursery.

There is a very London quality to the whole thing: important work tucked behind an ordinary public doorway. Visitors come to the Horniman for the famous overstuffed walrus, the musical instruments, the gardens and the views over the city. Families move through the aquarium looking at jellyfish, frogs and fish. Meanwhile, behind the scenes, under carefully programmed artificial moons, coral is being coaxed into new life.

The public does not usually see much of the laboratory itself. Like many of London’s stranger and more consequential rooms, it exists just out of sight. But the Horniman is currently connecting its hidden research to the wider world through a free display, Project Coral and the Journey of Hope, which runs until 12 July 2026. The display links the south London lab work with reef restoration efforts at Hope Reef in Indonesia, showing how research carried out in Forest Hill can support conservation far beyond the capital.

There is no simple rescue story here. A laboratory in London cannot, by itself, save the world’s coral reefs. The threats are too large: climate change, warming seas, damaged ecosystems, political delay, human appetite. Coral restoration is not a magic spell. It is one tool among many, and it only makes sense alongside serious action on the conditions damaging reefs in the first place.

But Project Coral does something valuable. It gives scientists control over a process that was once frustratingly brief and unpredictable. It turns a rare night-time event into something repeatable. It allows researchers to ask better questions and test possible answers. It makes reef conservation less dependent on waiting for nature’s annual moment of permission.

And there is something quietly wonderful about where this is happening. Not on a tropical island, not beside a turquoise lagoon, but in Forest Hill, in a museum founded from a Victorian tea fortune, better known to generations of Londoners for a walrus, a clocktower and school trips.

London is not where coral reefs belong, but, in one corner of south London, it may be helping them survive.