BioEd Online

The picture on the right shows the Elena glacier in East Africa's Rwenzori Mountains. It is part of one of the world's handful of equatorial ice fields — ice that geologists think has been been a permanent fixture here for 300,000 years. But in two decades, they say, it will be gone.

A recent survey shows that the ice field straddling the border between Uganda and the Democratic Republic of Congo now covers less than a single square kilometre. A century ago, it was roughly seven times this size.

The Elena glacier is retreating by between 10 and 15 metres each year, says Richard Taylor of University College London, who led the survey. The two images show the extent of the retreat over just 30 months.

Taylor and his team surveyed the terrain and compared satellite images to show how the ice fields have halved in size between 1987 and 2003. They publish their findings in Geophysical Research Letters¹.

The first survey of the extent of the ice field was carried out in 1906; this suggested that the mountains sported a snowy crown covering 6.5 square kilometres. Detailed climate data only extend back to the 1960s, says Taylor, but suggest that temperatures are rising by around 0.5 ºC each decade.

"We think rising air temperature is the most compelling factor," says Taylor. Lack of precipitation at the end of the nineteenth century may have begun shrinking the glaciers, he says, but it looks as if Africa's warming climate will kill them off.

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