Glaciers will vanish from the Pyrenees mountain range within the next 30 years because of climate change and pollution, scientists have warned.

Glaciers have already shrunk by half in the past 20 years in the mountains on the border between France and Spain, according to a new report by scientists who monitor them for the local environmental group Moraine.

“Pyrenean glaciers are doomed,” said Pierre René, an expert on glaciers. Mr René said it was impossible to give an exact date for their disappearance, but predicted that it would happen by 2050.

The glaciers feed rivers and contribute to biodiversity. Their ice also helps keep mountainsides stable.

The report by the group, which has measured the length, surface area and thickness of nine of the 15 glaciers in the French Pyrenees for 18 years, says they are now shrinking at an annual rate of 3.6 hectares (nearly 8.9 acres).

The surface area of the nine glaciers now totals 79 hectares (195 acres) compared with 140 hectares (346 acres) 17 years ago.

“We are seeing the disappearance of the symbol of the Pyrenean landscape in the high mountains,” Mr René said.

He said mountainsides may begin to crumble without the “cementing effect” of glacier ice, making climbing and hill walking more dangerous.