Manolo, age 10: "Will we still be able to live on the beaches in 30 years' time?"

In general, the simple answer is no! But in truth, it's a complicated question, encompassing at least three issues.

Frédéric Bouchette, University of Montpellier

First of all, the retreat of the shoreline that separates the sea from the land (known as the coastline) is a phenomenon observed by all. In 30 years' time, this retreat will be even more marked in many places.

In other places, beaches are widening every year, sometimes by several metres. In fact, the width of the beach depends in part on the movement of the coastline, which evolves over time in a totally bizarre way!

Surprisingly enough, coastline movement is one of the most complex issues in coastal research. So, when the coastline is stable, you can live close to the beach for a long time. On the other hand, in very dynamic areas, a house facing the beach can find itself far from the water or even underwater in just a few years.

On the other hand, it is often said that rising sea levels due to global warming are reducing the size of beaches. In fact, they adapt by rebuilding higher and higher, compensating for rising water levels. But they can only adapt in this way if there is a sufficient quantity of sand at the location in question. Where sand is in short supply, the beach shrinks all the faster as the water level rises.

What's more, even if the beach reconfigures itself with sea level, there's nothing to stop the water passing behind the beach, into the wetlands on land, which can't react like the beach system. This phenomenon is gradually transforming some coastal areas into islands, and it's not easy to live on an island, for many reasons, such as access, water resources or exposure to storms.

Finally, your question is probably as much a question of law, morality, ecology and economics as of physical science. How far are we willing to develop technologies and invest resources to live by the water?

On these issues, there are many discussions between the scientists who propose solutions, the local authorities who are concerned about preserving their territory, and the State, which has to regulate all this. We're bound to be living near beaches in 30 years' time, but we need to decide how now.

Frédéric Bouchette, Lecturer, University of Montpellier

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