The benefits and downsides of building into the sea

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Dubai has been building extensively into the sea (Credit: iStock)
As urban areas get more crowded, building new land and even floating homes is becoming more economic – but is it storing up future problems?

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This story is part of a series inspired by the subjects and speakers appearing at BBC Future’s World-Changing Ideas Summit in Sydney on 15 November. Find out more about the inspiring people coming to the meeting, including:

  • Researcher and TV presenter Emma Johnston on the impact of cities on oceans 
  • BBC TV presenter Michael Mosley on the science of food and health
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All around the world, cities are edging further into the sea. Plans are afoot to build huge islands and giant constructions in coastal areas, featuring the dredging and dumping of million of tonnes of material.

What are the implications for ocean life and ecosystems as we build more and more into the ocean? This is one of the questions that will be discussed at the BBC Future’s World-Changing Ideas Summit in Sydney in November.


Cities have been creeping further into the ocean ever since we first starting building harbours. Land reclamation is big business and today, numerous countries are ‘taking back’ land from the sea to expand their coastlines and territory.

Almost every coastal province in China has projects underway to build out the coastline, either by dumping soil from the mainland, dredging it up from further out to sea, or by blocking river estuaries and allowing the silt to build up.

The island-state of Singapore has added 22% onto its size over the past 50 years by building out into the surrounding waters using sand, earth and rock quarried and purchased from elsewhere. Their fervour for reclamation is such that they are the world’s largest importer of sand.

But it is Dubai that is home to perhaps the most famous of reclaimed areas. Its visually spectacular and entirely artificial Palm Jumeirah archipelago, home to the obscenely wealthy, is built from an estimated 110 million cubic metres of dredged sand.

And as one of the most densely populated nations on Earth, the low-lying Netherlands has long been driven to reclaim large swatches of its coastal swamps and marshes to house its ever-growing population.

Building into the sea can cause havoc for ocean ecosystems (Credit: iStock)

Building into the sea can cause havoc for ocean ecosystems (Credit: iStock)


For ocean ecosystems, certainly. Emma Johnston at the University of South Wales, who will be speaking at BBC Future’s World-Changing Ideas Summit, argues that we ought to think more about the impact of ‘marine urban sprawl’. Even more minor coastal constructions can transform the seas. She and her colleagues estimate that some estuaries in Australia, the United States and Europe have had more than 50% of their natural coastline modified with artificial structures.

“The reality is that urban sprawl is no longer just a land-based problem,” she wrote in an article for The Conversation. “Developments are spreading out into the oceans, creating tangles of structures beneath the water’s surface.” This causes havoc for marine organisms and their habitats, destroying the coral reefs that nourish fisheries and protect the coastline from the harsher impact of the waves, and destablising many precious coastal ecosystems such as salt flats and mangroves.

Building on dredged sediments also has risks for inhabitants, as this strata isn’t as stable as hard bedrock on land. There have been reports that Dubai’s Palm Jumeirah archipelago is actually sinking. Reclaimed land is also a risk in earthquake-prone areas. The prolonged shaking can trigger a process called liquefaction, where the once-solid sediments of reclaimed areas can liquefy. This was a significant contributor to the devastation of the huge San Francisco earthquake of 1906.


Given that land reclamation tiptoes the line between earth and sea, disputes over sovereignty keep lawyers of both very busy indeed. China’s efforts to build up coral atolls using sand, and reclaim more than 3,200 acres of land in the south-eastern South China Sea has been particularly controversial, not least because many of these new islands are now housing military facilities. While China has claimed sovereignty over these new islands, numerous countries – including the US and Australia – do not acknowledge this. In July this year, the International Court of Arbitration in The Hague also ruled that China had no historical claim to the region but sabre-rattling continues and there is no sign of an agreement on the horizon.

China's efforts to build new land have courted controversy (Credit: Getty Images)

China's efforts to build new land have courted controversy (Credit: Getty Images)


It’s not impossible. Floating villages have been around for a long time. In Cambodia, residents of the Tonle Sap freshwater lake live in floating houses. Similarly in Perus Lake Titicaca, the Uros people live on floating islands made from bundles of reeds. Around the world, architects are building more modern floating homes, especially in countries such as the Netherlands which is vulnerable to flooding.

Hi-tech floating cities or larger-scale habitats haven’t quite made it to reality, but that hasn’t stopped organisations such as the Seasteading Institute from challenging designers to come up with their visions of what futuristic floating cities might look like and how they might function. Their intention is not only to create new sustainable communities, but also to provide a hot-house environment for ‘start-up cities’, that bring a start-up mentality to urban development.


This gets into somewhat more fanciful territory. Bond villain and megalomaniac (aren’t they all?) Karl Stromberg may have had a vision of a new underwater civilisation in The Spy Who Loved Me, but in reality we haven’t got particularly far with that.

Florida International University still operates an underwater lab called Aquarius  

Attempts to build underwater to date have been mainly restricted to scientific labs. One of the earliest underwater habitats was set up in 1962 by Jacques-Yves Cousteau and his team. Conshelf I sat 10 metres below the surface of the Marseilles coast, and for one week, it was home to two ‘oceanauts’ who enjoyed all the mod-cons including television and a library. They followed it up with a small village on the floor of the Red Sea that was occupied for a month, and eventually Conshelf III, built one hundred metres below the surface near Nice in France in 1965, home to six oceanauts for three weeks at a time. Around the same time, Nasa and the US Navy also set up their own underwater laboratories – Tektite I and II, and Sealab. And Florida International University still operates a lab called Aquarius, nine kilometres off Key Largo, with space for six researchers, a kitchen and a laboratory space.

There are signs of more luxurious undersea properties coming soon though. Plans are afoot for underwater hotels in Australia, Dubai, the US and in the south Pacific. For example, the Water Discus Hotel, mooted for the Great Barrier Reef and off the coast of Dubai, will consist of an underwater and an above-water ‘disc’, with a connecting vertical shaft that avoids decompression issues.

But how those might come to affect the oceans and underwater ecosystems remains to be seen.

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