by Editor’s Note: Call to Earth is a CNN editorial series dedicated to reporting on the environmental challenges facing our planet, along with the solutions. Rolex’s Perpetual Planet initiative is partnering with CNN to promote awareness and education around key sustainability issues and to encourage positive action.
Miami Beach, Florida is famous for its turquoise and artistic flair. But just off the coast of this colorful city an underwater world is disappearing.
Florida’s coral reefs span nearly 563 kilometers (350 miles) and contain approximately 40 species of coral that not only provide food and shelter for aquatic life, but also help protect coastal communities from storm damage.
Like other coral reefs, over the past few decades, this vibrant ecosystem has been suffering from the effects of climate change, with the National Oceanic and Atmospheric Administration recently reporting the fourth major global bleaching event – the second to last ten years.
Bleaching occurs when corals become stressed due to changes in their environment and the removal of the colorful algae that live on them. The corals turn white and begin to weaken.
“If the bleaching continues for a long time, the corals die,” says Diego Lirman, associate professor of marine biology and ecology at the University of Miami.
Lirman runs the Rescue a Reef lab, which aims to help preserve and restore this precious and still fragile habitat. “Coastal ecosystems protect our shores from the impacts of storms and waves,” says Lirman. “The speed bumps are the sea.”
Off the coast of North Miami Beach, he is leading an underwater experiment that combines natural coral with an artificial structure – creating a hybrid reef that he hopes will mimic the effects of a real one.
“The speed of the sea beats”
Increasingly, artificial reefs are being implemented around the world to help restore marine ecosystems – from 3D printed tiles to sunken ships. Studies suggest that artificial structures can be effective, but factors such as location, design and placement can influence the outcome. In 2009, the UN International Maritime Organization provided guidelines for the placement of artificial reefs, noting that these reefs can have a negative impact “especially when waste, recycled or unsuitable materials are used.”
Lirman’s ECoREEF hybrid project consists of a concrete foundation covered with corals transplanted from his nurseries.
The experiment was born in the laboratory, where many tests were carried out on model versions, including extensive simulations in a powerful wave generator capable of recreating the conditions of a category 5 hurricane.
Lirman says the base alone can reduce wave activity by 60 to 70%, and corals by a further 15 to 20%.
“Together, these two approaches can reduce wave energy and wave height by about 80 to 90%, which is what we want to protect our shorelines,” Lirman tells CNN.
In partnership with the city of Miami Beach, two hybrid reefs were deployed in March 2023. Over the past year, Emily Esplandiu, a research associate in Lirman’s coral restoration lab, says they have seen different species of fish colonizing the reef, along with turtles. , sharks and rays.
She tells CNN that they saw the corals they planted grow and grow there too. “So now we can look at how different species and genotypes survive in these conditions and how resilient they are through high temperatures,” she says.
Coral gardening
Lirman’s team has been growing and testing coral colonies at the university for over 15 years.
“We’re trying to understand why some corals survive and others die in the same environment,” says Lirman. “We are learning[ing] from the survivors, what about their physiology, their genetics? And then we’re using that information to create climate-resilient corals.”
The lab is also experimenting with “stress hardening,” where researchers expose corals to sub-lethal temperatures to prime their physiological response, making them less vulnerable to changing ocean temperatures. The corals are then transplanted onto natural reefs or the hybrid structures.
Each year, his team plants 10,000 to 15,000 corals on Miami-Dade’s reefs, Lirman says.
In the next few years, Lirman and his team plan to significantly expand the scale of the ECoREEF project, deploying larger structures throughout the Miami area, thanks to funding from the US Department of Defense.
“They realized that the health of coastal ecosystems is a national security issue when storms affect their coastal base, and then they can’t do their job,” Lirman tells CNN.
A global problem
Ocean ecosystems are declining and suffering around the world, says Lirman.
The main threat to corals worldwide is climate change, which is increasing sea temperatures and leading to changes in storm patterns and ocean chemistry. Overfishing and dredging also play a role, Lirman says. As a result, coastal areas are becoming more exposed to waves and flooding.
“After every storm, the cost of rebuilding and the loss of property and life, it’s huge,” says Lirman. “We need to protect our shorelines and nature-based solutions [like] Hybrid reefs are one efficient, cost-effective way to do that.”
While Lirman hopes his experiment will serve as a model for other ocean cities around the world, he says we need to curb climate-warming carbon emissions – “if we don’t do that, no amount of artificial reefs will save our coasts. “
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