Saving Caribbean corals with concrete

By Steph Andrews

Artificial reefs are man-made, underwater structures installed to provide a substrate and shelter for organisms. For centuries, they have been used to increase local fish populations and their ability to replicate natural environments means they can be used to mimic globally declining natural reefs.

The Grand Anse Artificial Reef Project (GAARP) is a grassroots project based in Grenada, a small island in the south Caribbean. Six years ago, the small team launched their first concrete pyramid – a stack of breeze blocks – into the Caribbean Sea off Grand Anse beach. GAARP’s project lead explains: “around the world, reefs which have taken hundreds, if not thousands, of years to reach maturity are dying. I want to think of a way to boost start them.”

Now numbering 30, the concrete reef supports marine wildlife which relies on an increasingly threatened natural environment. This unconventional but successful method could provide coastal managers with a way to alleviate some of the problems facing coral reefs and coastal communities.

Coral reefs

Coral reefs are some of the most spectacular and diverse ecosystems in the world. These marine oases, often thousands of times more productive than the open sea, nurture complex habitats by providing refuge from predators and environmental stressors.

Human activity directly threatens an estimated 50-70 percent of coral reefs. In the Caribbean, average hard coral cover has decreased about 80 percent since the early 1980s.

Coral decline has natural and human causes: extreme events can flatten reefs and recent Caribbean hurricane seasons have been some of the most active on record. Marine herbivores, which reduce competitors like algae, have been lost through disease and overfishing.

Humans have over-exploited reefs, caused physical damage e.g. by dropping anchors and caused eutrophication through run-off of terrestrial chemicals like pesticides. Mass coral bleaching as a result of warmer seas has resulted in significant global coral loss.

Experts believe the unprecedented and persistent changes to Caribbean coral reefs could mean that human activity has irretrievably compromised their health. Losing these environments has serious consequences for wildlife, ecosystem functioning and environmental services.

GAARP

Phil Saye owns beachfront dive shop ‘Dive Grenada’ and is the mastermind behind GAARP. He explains that building the artificial reef is part of his conservation and philanthropic work: “I wanted to give back and see what would work for marine conservation. Around the world, there are lots of reefs dying so I thought about building an artificial reef.”

A delivery of concrete blocks to the adjacent hotel was the unlikely inspiration for GAARP, Phil explains. “I sat there like a small boy with Lego and built a pyramid. The shape is perfect: the design is stable and doesn’t negatively impact the marine environment.”

Phil built the first two pyramids on wooden pallets on the beach. He launched them in 2013 and sank them about 200 hundred yards off the coast in a desolate, sandy area.

After three months, long spine sea urchins, herbivorous ‘housekeepers’, colonised. Species richness grew and Phil made a surprising discovery: “I was told very forcefully that coral would never grow on there. After two years, I saw a tiny piece of coral the size of a fingernail. Coral polyps had found the pyramids in their first year and started to grow. There are corals – many different types – growing all over them now.”

Six years on, the cluster of 30 pyramids has become a tourist attraction: “People have got to know about it and they absolutely love it. They can’t believe that something so shallow – it’s only 3m deep – is working so well”. The pyramids now support over seven coral and 30 fish species.

Thinking bigger

Phil admits there is a long way to go until the pyramids can replicate the variety of wildlife found on a natural reef, but conservation is only part of his mission: “I started with orphanages and children’s homes. I bring children down, swim out with them and educate them very softly on marine conservation. I see it as my job to switch the light on; in the future they might be in a position to make a difference.

“I want to create something which is transferrable around the world. You could scale the pyramids up, produce them cheaply, plant them near your community and if you’re smart, you can have a sustainable fishery. It’s not just about producing artificial reefs – we’re also making sustainable fisheries and livelihoods for the local community.”

GAARP gained formal government permission to sink the pyramids in 2017. Like many governments in small developing countries, the Grenadian government must balance sustainable coastal management with creating opportunities and maintaining livelihoods.

Peter Thomas, Assistant Director of Grenada’s Science and Technology Council, explains that although climate change is high on the government agenda, lack of manpower, equipment and political drive hinders action – but he is confident this is gathering momentum.

A significant milestone in coastal management came a decade ago when sand mining was outlawed. Despite early warnings, the lucrative business continued until its negative impacts were impossible to ignore. Mr Thomas explains the conflict between making money, providing jobs and preserving Grenada’s coastline: “you say no to sand mining because the island is disappearing, but others say yes because they are making money.”

The future?

Vigilance and the input of schemes such as GAARP mean that in many areas, Grenada’s coastline is successfully recovering from human degradation. Mr Thomas says this has led to the “beefing up” of social and economic activity in coastal regions, including tourism and fishing.

Ilana Zalmon, a professor of marine biology at the State University of Northern Rio de Janerio, explains that artificial reefs are “excellent instruments for…management of fisheries, maintaining coastal habitats, aquaculture, tourism locations and conservation of biodiversity.”

Citing examples from Australia which compare artificial and natural reefs, Professor Zalmon says: “These publications have showed artificial reefs as important zones for species attraction and also as strategic areas for natural reef conservation…artificial reefs have the potential to fulfill many of their intended purposes.”

Stressing the importance of careful planning, monitoring and continual management, Professor Zalmon explains that “artificial reefs may help to protect coastal areas and increase biodiversity.”

Despite the success of projects like GAARP, artificial reefs cannot identically replicate fully functioning natural reefs. As one of the most vulnerable marine environments, coral futures rely on understanding and addressing the chronic causes of mortality and developing effective management strategies which complement adaptive projects.