The battle for the coast
The million dollar question: how bad will it be?
Climate change is placing increasing pressure on coastal regions which are already seriously affected by intensive human activity. This raises the question of whether – or to what extent – these areas will retain their residential and economic value in the decades and centuries to come, or whether they may instead pose a threat to the human race. Also, we do not know what changes will occur to the coastal ecosystems and habitats such as mangroves, coral reefs, seagrass meadows and salt marshes that provide the livelihood of coastal communities in many places.
Scientists have tried in various studies over recent years to assess the extent of the threat posed by sea-level rise. To appreciate the coastal area at greatest risk of flooding, it is necessary to first analyse current heights above sea level. This is not easy because no reliable topographical maps yet exist for many coastal areas. At a rough estimate more than 200 million people worldwide live along coastlines less than 5 metres above sea level. By the end of the 21st century this figure is estimated to increase to 400 to 500 million.
- 3.12 > Bangladesh experienced the full force of Cyclone Aila in 2009. Thousands of people lost their homes. This woman saved herself and her family of five in a makeshift shelter after the gushing waters burst a mud embankment.
- During the same timeframe the coastal megacities will continue to grow. New cities will be built, particularly in Asia. In Europe an estimated 13 million people would be threatened by a sea-level rise of 1 metre. One of the implications would be high costs for coastal protection measures. In extreme cases relocation may be the only solution. A total of a billion people worldwide now live within 20 metres of mean sea level on land measuring about 8 million square kilometres. This is roughly equivalent to the area of Brazil. These figures alone illustrate how disastrous the loss of the coastal areas would be. The Coastal Zone Management Subgroup of the IPCC bases its evaluation of the vulnerability of coastal regions, and its comparison of the threat to individual nations on other features too:
- the economic value (gross domestic product, GDP) of the flood-prone area;
- the extent of urban settlements;
- the extent of agricultural land;
- the number of jobs;
- the area/extent of coastal wetlands which could act as a flood buffer.
- 3.13 > On the North Sea island of Sylt, huge four-legged concrete “tetrapods” are designed to protect the coast near Hörnum from violent storm tides. Such defence measures are extremely costly.
- A quite accurate estimate has now been made of which nations would suffer the most because a large percentage of the population lives in coastal regions. Bangladesh and Vietnam are extremely vulnerable. Nearly all the population and therefore most of the national economy of the low-lying archipelagos of the Maldives and the Bahamas are now under threat. In absolute numbers China is at the top of the list.
The most vulnerable regions in Europe are the east of England, the coastal strip extending from Belgium through the Netherlands and Germany to Denmark, and the southern Baltic Sea coast with the deltas of Oder and Vistula rivers. There are also heavily-populated, flood-prone areas along the Mediterranean and the Black Sea, such as the Po delta of northern Italy and the lagoon of Venice as well as the deltas of the Rhône, Ebro and Danube rivers.
Some densely-populated areas in the Netherlands, England, Germany and Italy already lie below the mean high-water mark. Without coastal defence mechanisms these would already be flooded today. For all these regions, therefore, the question of how fast the sea level will rise is extremely important and of vital interest. We need to resolve how we can intensify coastal protection right away, how society can adapt itself to the new situation, and whether it might even be necessary to abandon some settlements in the future. Without appropriate coastal protection, even a moderate sea-level rise of a few decimetres is likely to drive countless inhabitants of coastal areas in Asia, Africa and Latin America from their homes, making them “sea-level refugees”. The economic damage is likely to be enormous. The infrastructure of major harbour cities and especially regional trading and transportation networks – which often involve coastal shipping or river transport – would also be affected. Experts have prepared a detailed estimate of the implications of rising sea levels on Germany’s coastlines. >