"The quiver trees are in the early stage of a poleward (southward) range shift," Wendy Foden, a researcher at the South African National Biodiversity Institute, told a conference on climate change science in Johannesburg.

A shift towards the poles and away from the equator is precisely what one would expect as a response to warming conditions, Foden said.

She said observations at over 50 sites throughout the trees' range in Namibia and South Africa highlighted two disturbing trends which could clearly be linked to climate change.

The first was that with populations found on slopes, mortality was much higher at lower elevations than at higher ones -- that is, where it would be warmer on a slope.

She also found higher mortality rates in the north of its range, towards the equator, than those found in the south.

Historical data from weather stations within the trees' range also showed rising temperatures over the past few decades.

"If there is no expansion in the quiver trees' range, then models forecast a 76 percent reduction in its population over the next 100 years," she said.

"Even with dispersal its numbers could be down over 30 percent over the next century," she said.

She also said the quiver trees' situation highlighted the fact that climate change was having an impact on desert ecosystems, regions where many people assume the affects should be minimal as they are already hot and dry.

Dr Richard Pearson of the American Museum of Natural History told the conference that a species had three choices when confronted with climate change: die, adapt or migrate.

For the quiver tree, any migration it made would have to come about as a result of seed dispersal via the wind or from droppings from birds or other animals that digested them.

That may help the species but not individuals, some of which are over 150 years old.