VIENNA, Austria — Add glaciers to the list of things endangered in nature.

Glaciers will all but disappear from the Alps by 2050, scientists warned Monday, basing their outlook on mounting evidence of slow but steady melting of the continental ice sheets.

In western Austria's Alpine province of Tyrol, glaciers have been shrinking by about three per cent a year, meaning their mass decreases annually by roughly a metre, said Roland Psenner of the University of Innsbruck's Institute for Ecology.

And 2050 is a conservative estimate, he said: If they keep melting at that rate, most glaciers could vanish by 2037.

"The average density of glaciers in the Alps is 30 metres, so it seems rather certain that there won't be any more glaciers except for a few high ones that lay above 4,000 metres,'' Psenner said.

Experts at a regional conference on the Alps, held annually in the mountain resort of Alpbach, stopped short of blaming global warming. But they called for a review of preventive measures to protect people living in valleys who could face a higher risk of dangerous flooding.

Runoff from melting glaciers caused severe flooding that devastated parts of Switzerland in the summer of 2005.

Glacial melting is a global problem, according to the Zurich-based World Glacier Monitoring Service, which keeps tabs on 30 ice sheets in nine mountain ranges worldwide and says their average mass is steadily eroding.

Glaciers are the planet's largest source of fresh water after polar ice, which scientists say also is melting to 100-year lows. In Europe, they're also hugely popular with skiers and snowboarders seeking year-round thrills and help anchor a multimillion-dollar tourist industry.

In 2005, glacier thickness decreased by an average of 60 centimetres, and in 2004 by an average of 70 cm, the Swiss agency said, citing preliminary measurements.

Since 1980, it said, Europe's glaciers have lost about 9.6 metres of ice. About 2.5 metres melted away in a single summer -- 2003 -- when a heat wave zapped much of Europe, said Michael Zemp, a glacier expert at the University of Zurich.

"What's important for a glacier is winter snow accumulation and a cold summer with not a lot of melting,'' Zemp said Monday in a telephone interview. "A bad year for a glacier is a dry winter and a hot summer, and these are the conditions we've been seeing.''

Forecasting their demise is problematic "because we don't know what scenarios there will be, and there are a range of scenarios. This isn't a weather forecast. But we are seeing an accelerated glacial melting.''

In the 13 years spanning 1991-2004, twice as much glacial ice melted in Europe than in the 30 preceding years, climatologists say.

Underscoring a glacier's vulnerability, for every 1 C rise in temperature, it needs a corresponding 25 per cent increase in precipitation just to maintain its mass.

A few glaciers have more staying power: Switzerland's Great Aletsch Glacier is still 800 to 900 metres thick and seems destined to survive well into the 22nd century.

But data collected by aircraft and satellites since 2002 show that many of Earth's estimated 160,000 glaciers from the Rocky Mountains to the Himalayas have been shrinking.

Scientists say the phenomenon has been occurring for more than a century, suggesting that man-made emissions of carbon dioxide are combining with purely natural factors, such as a shift in jet streams pumping warmer air into traditionally cooler northern climes.

Even in Austria, a relatively sparsely populated country of 8.2 million people, passenger cars alone chug some 10 million tonnes of carbon dioxide into the atmosphere each year, the nation's leading automobile club said Monday.

It urged commuters to consider walking or cycling to work, and called on motorists to ease back, saying a recent study showed that every 10th drive covers less than a kilometre -- a distance easily travelled on foot or with a bike.