Common seals in the Somme Bay, France (50°13’N, 1°31’E).

For a distance of more than 40 miles (70 km) along the English Channel, land and sea intermingle at the heart of a vast coastal wetland –the maritime plain of Picardy, famed for its rich bird life. Some 340 species of birds either nest there or use it as a stopover during their great spring and autumnal migrations to warmer climes. Here you will also find the largest colony of common or harbour seals (Phoca vitulina) in France, with a population of over seventy. Summer is the season of births. At ebb tide the seals come with their pups to rest on the sandbanks which the tide has uncovered. Tranquillity is essential, for if the seals are disturbed, they will rush back to the sea, and the pups, which have not yet been weaned, may lose their mothers in the chaos and thus be condemned to almost certain death. The maritime plain of Picardy is one of the largest natural wetlands in France, and such fragile ecosystems are among the most fertile on Earth, even though they only cover a small area. During the last thirty years, half of France's wetlands have been lost or degraded.