Planting trees underwater

Fish stocks are declining around the world. Overfishing, climate change and continued coastal development are putting pressure on our oceans. To help restore much-needed balance, Australian underwater architects are building artificial “forests” underwater. Barbara Barkhausen reports from Sydney.

Underwater architects want to install artificial reefs along Australia's coasts. (Photo credit: amazize, flickr)

Underwater architects want to install artificial reefs along Australia’s coasts. (Photo credit: amazize, flickr)

Planting trees underwater sounds completely crazy at first. Except that the trees from Australia’s Haejoo Group have nothing to do with what grows in our gardens. Reef designer Ryan Paik has instead created gigantic skeletal structures – cubes, domes and pyramids – out of concrete and steel, which he then submerges into the sea.

Fish don’t want a “bare” sea

Fisherman and divers have known for a long time that algae, corals, barnacles, sponges and fish settle in underwater structures in just a few short months. Old shipwrecks, sunken ships, old cars, even shopping carts that sink in the sea attract marine life of all kinds. But the more bare and empty the sea, the more uncomfortable the fish. Add to this the problems of overfishing and the increasingly warmer and acidic ocean waters, and it’s clear why fish populations are steadily decreasing.

But throwing garbage and scrap into the sea is hardly the solution. Which is where the Haejoo Group steps in. It develops special reef modules whose shape and size can be tailored to the needs of a region and the fish that reside there. Every fish species has its own preferences with respect to shape, surface, cavities and the profiles of the modules.

Greater biodiversity in artificial reefs

Ryan Paik calls them his marine forests; others would say he’s creating “apartment buildings” for fish. “The fish like the cavities in the structures, they feel comfortable there,” says Paik. “Artificial reefs promote more biodiversity in the long run than natural ones.”

Paik comes from South Korea, where artificial reefs are well established – just as they are in Japan – as a measure to counter overfishing. The Haejoo Group installed an artificial reef around one kilometre off the Sydney coast that was sponsored by the fisheries authorities. The reef sits 38 metres underwater, weighs 40 tonnes and is 12 metres tall at its highest point. “In Sydney, they wanted to attract more mackerel and swordfish than the fisherman can fish,” explains Paik. And it worked: The artificial reef was inhabited with marine life – growing on the structure, swimming between the beams – in just six months.

Help for the Great Barrier Reef

Artificial reefs could play an even more important role along Australia’s northeastern coast, where natural reefs such as the famous Great Barrier Reef have been suffering for years: According to a 2012 study, the Great Barrier Reef has lost more than 50 per cent of its coral in the past 27 years. Ocean acidification is one of the reasons behind this alarming trend.

If artificial reefs could be created in the coastal waters off the reef – which are especially vulnerable and weakened due to runoff from agriculture and numerous coal ports – it could help the underwater plants, sponges and corals curb the acidity of the water. “Moreover, we could restore damaged ecosystems and relocate corals from other regions, such as when a new shipping canal is being dug,” says Paik.


Photo credit: amazize, flickr/Creative Commons

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