New fears on sea-level rise

Abstract

Rising sea levels are beginning to bite. Nigel Williams reports. Rising sea levels are beginning to bite. Nigel Williams reports. Countries based on coral atolls have led the fears about rising sea levels but the issue of global warming, which is contributing to rises in sea level, is out of their hands and in those of the major industrial nations. But this is not stopping growing alarm amongst such island states, some of which rise only a few metres above mean sea level. In Tuvalu in the southern Pacific, where land reaches no more than four metres above mean sea level, fears are growing for an ecological and social disaster. Sea-level gauges in the main island of Funafuti are now recording an average annual rise of 5.6 mm. With the presence of king tides, and exposure to cyclones, residents of Tuvalu increasingly believe that their days on the coral atolls and the future of the coral island ecosystem are numbered. Of all the low-lying nations threatened by sea-level rise, Tuvalu has been one of the most vocal in the international arena. It recognised the threat early on, and successive governments have lobbied hard to alert the outside world to its predicament. It is not so much the prospect of the islands gradually being swamped that worries the locals. It is the extreme weather events that are already occurring as sea levels rise which they believe will make the islands uninhabitable long before they are submerged. The locals also fear for their coral reefs, which they say are bleaching, and fishermen are having to travel further afield for diminishing catches. “There will come a point when we can't grow anything in the ground, when the trees start dying and we can't get shelter,” says one of Tuvalu's prime minister's advisers. The so-called king tides are a new phenomenon. When they strike, the land is almost level with the ocean, and waves break right across the island. The water table is so high that it seeps up through the earth. What everyone fears is a cyclone coinciding with a king tide. While low-lying countries continue to worry increasingly about sea-level rises, many of whom have few resources to tackle it in any serious way, some industrial countries are also beginning to feel the pressure. The UK, which is one of the major contributors to greenhouse gas emissions through its long industrial history, is now becoming increasingly worried about its capital, London. According to a recent report by the International Panel on Climate Change, predictions of sea-level rise are around 3.1 mm per year. The low-lying city built a flood barrier across the River Thames more than 20 years ago to help protect it from surge tides and floods. But the problem is exacerbated by the geological tilt of Great Britain into the sea in the east — where London is — and a rise of land in the west following the last ice age. A new intensive study using three separate technologies to make measurements over the past decade has found that the subsidence rate in parts of the capital is up to 2.1 mm per year. This rate of sinking magnifies the rise in sea level by more than 60 per cent — so the combined effect approaches the rate facing Tuvalu. The Thames Barrier was built knowing that it had a finite lifetime. It was conceived following disastrous floods and considered to be viable until at least 2030. But the British Environment Agency is now considering what should succeed the barrier and climate change is accelerating thinking about how to try to protect the millions of people in London. One scheme being considered is the use of large areas of marshland as floodwater storage areas, which are home to some of the most important wetland bird habitats in Europe. But such concentrated thinking may also help focus attention on the plight of coral-island dwellers and their marine environment in places such as Tuvalu.