Tourism's demands are sometimes heavy

He says the Alps are "probably the world's most saturated tourist region, as well as being perhaps the most fragile ecosystem".

"Despite all the commandments and entreaties in every tourist office and along every path," he writes, "there is still too much litter, too many fires, as well as wanton destruction of rare fauna and flora and desecration of the cultural heritage."

The World Wide Fund for Nature (WWF) says: "Mountain parks have been identified as especially at risk from the environmental destruction caused by climate change.

Changes found

"As the climate warms, species that live in the higher Alpine zones are forced to move higher on the mountain to find suitable habitat, and this can drastically reduce the living area available to them," warns the organisation.

Off-piste skiing can bring problems

"Scientists have already recorded changes in Alpine vegetation as a result of global warming; if the rate of climatic change continues to accelerate, then the extinction of some mountain plants and animals is certain," it adds.

The WWF identifies the Swiss national park, the Majella national park in Italy, Hohe Tauern and Nockberge national narks in Austria, and Berchtesgarten national park in Germany as Euopes's most vulnerable areas.

Direct threat

But for the people who live year-round in the mountains, attempts to limit tourism are a direct threat to their livelihoods.

There are already signs that some of the cheaper package ski tours are opting for North America, where the season is longer than in the Alps.

Thoughtful tourists aim to "take away nothing but memories, and leave behind nothing but footprints".

Ideally, that is the way forward for the Alps. Practically, it remains an elusive goal.