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How To Grow A Living Reef From Iron And Seawater Financial Times;
Feb 10, 2001
Twenty people - including fishermen, the village blacksmith and marine scientists from Indonesia, India, Australia, Israel, the US, Jamaica and elsewhere - stagger under the weight of Ibu Karang or "the mother of all corals", a huge iron frame shaped like a giant tea cosy. Slowly, they carry it down the beach and into the sea. Floats are attached to the 12 metre structure and the crew swim with it 100 metres out to sea, release it from the floats and let it settle on the sandy bottom. Later, a small electrical circuit is created in the frame through wires from a solar-powered battery on shore. This scene, at Permuteran on the island of Bali in Indonesia, is one of the latest in a network of conservation projects using a technique called Biorock. The initiators believe it can make an important contribution to reversing the destruction of the world's coral reefs. Reefs provide about Dollars 400bn a year in directly measured benefits in such areas as fisheries and tourism, contributing to the livelihoods of about 500m people. But destruction is both relentless and rapid. Estimates made in 1998, that 11 per cent have been destroyed by human action, were recently revised sharply upwards to more than 27 per cent "effectively" lost by late 2000. The loss is mainly due to exceptionally warm seas, diseases resulting from stress, blast-fishing and pollution. Scientists think that at least another 25 per cent will go within 20 years, with global warming taking an even greater toll throughout the rest of the century. Once a reef is destroyed or severely degraded, recovery may take decades or hundreds of years, or never happen at all. Saving the reefs will mean improved systems of management, including no-take zones, and greater community involvement in their preservation. Restoring those that have been damaged or destroyed may be even more difficult but Biorock, or Mineral Accretion Technology as it is also known, suggests a way forward. After 20 years of painstaking work on shoestring funds, Wolf Hilbertz and Tom Goreau have shown how to grow a limestone base, and from that entire living reefs, using no more than a few iron bars, electricity and seawater. Biorock uses low-voltage direct currents, usually from tidal or solar energy sources, to grow solid limestone on conductive materials such as iron. The electrolysis causes calcium carbonate and magnesium hydroxide in the seawater to accumulate on the surface of the bars, and accelerates the growth and reproduction of coral attached to the bars. In natural circumstances, coral polyps feed on food particles in the water and also capture energy from sunlight-trapping microscopic algae called zooxanthellae, which are embedded in their outer surfaces. Electrolysis decreases acidity at the surface of growing Biorock, allowing calcium carbonate crystals to form which the coral uses to create its skeletal structure and so grow more rapidly. Without having to expend their own energy to create these favourable conditions, the corals can put more energy into growth and reproduction and withstanding stress. Over time, and with just the right voltage and current density, limestone rock, which is the natural base for coral, accumulates. The structure becomes ever stronger and the corals become firmly embedded in the structure as it grows. The technique can also be used to grow breakwaters or construction materials which otherwise have to be imported to atoll nations. Should the structure be damaged, it will "heal" itself in a few days by renewed deposition of minerals at the point of impact - a property normally only found in living structures. The mechanical strength of Biorock compares well to lightweight concrete. "Biorock can be made on any scale, and is viable for even the smallest and most remote communities, as well as the largest," says Hilbertz. "The skills for maintaining and repairing mineral accretion structures are quickly acquired locally. And no expensive foreign experts are needed to maintain them." Until recently, their work was largely neglected, but in 1998 Goreau and Hilbertz won international recognition with the Society for Ecological Restoration's prestigious Theodore M. Sperry Award. And now, in addition to projects in Bali, Thailand, Papua New Guinea, Mexico and Panama, schemes are under way in Israel, India and Sulawesi (Indonesia). There is also interest in Hawaii and the Philippines, while a 150-metre artificial reef is planned for Permuteran this month. Spectacular results achieved at a project in the Maldives have helped to make this surge of activity possible. During the El Nino event of 1998, more than 90 per cent of branching corals in the Maldives died from high seawater temperatures in a phenomenon known as coral bleaching. As a result, the dead coral framework began to collapse from the destructive activities of internal boring organisms and the heavy grazing of parrotfish, whose populations have exploded. Prospects for coral reef recovery are severely limited by the massive mortality experienced in all potential Indian Ocean source areas of new coral larvae. Rising temperatures could make bleaching an annual phenomenon in the near future. There is, therefore, a critical need to develop ways to protect coastlines from erosion, restore damaged reef structures, and maintain biodiversity if the Maldivian islands and their people are to survive global climate change. Commencing in 1996 Goreau and Hilbertz, together with local colleagues led by Azeez Hakeem, used Biorock to build reefs near the Ihuru Tourist Resort in the Maldives in the North Male Atoll. Before the bleaching event in 1998, the limestone accretion had grown to a thickness of 20cm on the bars in their structures. Coral fragments transplanted on to the structures grew three to five times faster than normal. One structure, known as the "Ihuru Necklace", built as a possible first part of an artificial reef to encircle the entire island, is 40 metres long, 8 metres wide and 1.5 metres high, and is powered by solar cells and batteries delivering the equivalent of just one 500-watt bulb. Following the bleaching event, corals on the "Necklace" and other Biorock structures had much higher survival rates than corals in surrounding reefs, while damaged coral on the structures grew back more than twice as quickly as the few surviving on neighbouring natural reefs. But coral recovery on the Bio-rock is far from plain sailing. "After bleaching, there was imbalance in the reef ecosystem," says Hakeem. "Many corals died but their enemies, such as crown-of-thorn starfish, did not die." The new baby corals are threatened by these creatures and require constant vigilance to protect them, he says. And fishermen are continuing to blast near existing structures in Bali and elsewhere. Some scientists are cautious about coral restoration efforts. "Telling people you can restore damaged reefs (may give) the false impression reefs are expendable, and can be destroyed now to be fixed later," says Robert Richmond of Marine Biology at the University of Guam. "There is always some mortality associated with transplantation exercises, and the result may be two damaged areas instead of one." The best approach, Richmond says, is to restore conditions that support natural recovery, including clean water and clean substrata. Nevertheless, he says, some steps can be taken to "fix" the reefs and, together with colleagues from Australia and Hawaii, Richmond is cultivating coral larvae and inducing them to settle on appropriate surfaces. Goreau agrees, in part: "Our view is that the best reef is a healthy natural one, and even the best Biorock one will be somewhat different. But sadly, to think that reefs will enjoy (more favourable conditions including) clean water and substrate that allow natural recovery is only a hopeful dream in a world that is moving in just the opposite direction."
Copyright: The Financial Times Limited 1995-2002 |
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