| BBC future world summit | building into the sea | land fill | floating homes |

As urban areas get more crowded, building new land and even floating homes is becoming more economic – but is it storing up future problems?

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.


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.