Hong Kong’s terracotta tile army marches to the rescue for coral

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In 2018, a super-typhoon destroyed 80% of the corals in Hoi Ha Wan bay off the Sai Kung peninsula in Hong Kong. In the city’s strongest storm since records began, winds reached 155mph (250km/h) and battered the reefs, leaving behind mostly scattered debris and broken coral skeletons. A few coral species survived, but these will likely take decades to regrow to their former state.

Sadly, this was no exception. Coral reefs are rapidly vanishing from the world’s oceans in large part because of the effects of global heating, which among other issues is increasing the frequency and severity of storms. In 2016 and 2017 alone, 89% of new corals on the Great Barrier Reef perished as a result of global heating-induced bleaching. Without decisive action to tackle the climate emergency, overfishing and pollution, it is estimated we will lose 70% to 90% of the world’s remaining coral reefs over the next 20 years.

A team of marine scientists and architects from the University of Hong Kong are trialling one method of restoring the reefs destroyed in the typhoon – and, they hope, others in future.

Using a 3D printer, they have created so-called “reef tiles” – hexagons made of terracotta – and placed them on the seafloor in Hoi Ha Wan bay.

The technology might be advanced but the idea is simple. “To create a hard bottom on a sandy seafloor,” says David Baker, director of the Swire Institute of Marine Science (Swims). “Sand is really not great for corals as it can move and bury or scour the coral’s thin tissues. Most corals that end up in sand usually suffer a slow death.”

The tiles, on the other hand, stand on feet that elevate them from the seabed – allowing corals to grow higher in the water column, where they can access all the things corals like: sunshine, nutrients and food.

The idea is being tested in other locations around the world: scientists are working to restore reef habitats with 3D printing in the Maldives, which is home to the world’s largest 3D-printed reef, as well as in France and the Caribbean.

Early results since the deployment last month have been promising.

“It’s encouraging that we see many species like small fish and crabs taking refuge in the tiles almost as soon as they touch the seafloor,” says Baker. “My hope is that the government will allow us to plant patch reefs that within my lifetime could be significant biodiversity hotspots, enjoyable dive sites, and contribute to increasing corals within Hong Kong through their reproductive output.”

https://www.theguardian.com/environment/2020/aug/26/hong-kongs-terracotta-tile-army-marches-to-the-rescue-for-coral

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