Tree Threatened by Climate Change
SOUTH AFRICA: October
JOHANNESBURG - A
famed desert tree used for generations by Africa's bushmen to make
quivers for their arrows is threatened by global warming, a
conference heard on Tuesday.
With a stocky trunk topped by a
tangle of forked branches, the quiver tree has iconic status in Namibia, where
its blue-green crown vividly stands out against a parched landscape.
"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
Historical data from weather
stations within the trees' range also showed rising temperatures over the past
"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.
"If you're a plant, quite
literally you are stuck," Foden said.
Story by Ed Stoddard
REUTERS NEWS SERVICE