[Editors] MIT team describes unique cloud forest

[Elizabeth Thomson]

MIT News Office
Massachusetts Institute of Technology
Room 11-400
77 Massachusetts Avenue
Cambridge, MA  02139-4307
Phone: 617-253-2700
http://web.mit.edu/newsoffice/www

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MIT team describes unique cloud forest
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For Immediate Release
THURSDAY, SEP. 14, 2006
Contact: Elizabeth A. Thomson
Phone: 617-258-5402
Email: thomson at mit.edu

PHOTO AVAILABLE

CAMBRIDGE, Mass. -- Trees that live in an odd desert forest in Oman 
have found an unusual way to water themselves by extracting moisture 
from low-lying clouds, MIT scientists report.

In an area that is characterized mostly by desert, the trees have 
preserved an ecological niche because they exploit a wispy-thin 
source of water that only occurs seasonally, said Elfatih A.B. 
Eltahir, professor of civil and environmental engineering, and former 
MIT graduate student Anke Hildebrandt.

After studying the Oman site, they also expressed concern that the 
unusual forest could be driven into extinction if hungry camels 
continue eating too much of the foliage. As the greenery disappears 
it's possible the trees will lose the ability to pull water from the 
mist and recharge underground reservoirs.

A report on their research was published in a recent issue of 
Geophysical Research Letters. They are also advising the Omani 
government on handling the problem.

The forest is especially unique, said Eltahir and Hildebrandt, 
because it "is a water-limited seasonal cloud forest" that is kept 
alive by water droplets gathered from passing clouds -- ground fog. 
The water dribbles into the ground and sustains the trees later when 
the weather is dry. The MIT work suggests the trees actually get more 
of their water through contact with clouds than via rainfall.

In general, cloud forests are not really rare. But they occur most 
frequently in moist tropical regions where there is ample rainfall. 
So it is unusual, the researchers said, to find a cloud forest in a 
region known for chronic dryness.

The researchers studied the area in Oman to learn how the Dhofar 
Mountain ecosystem "functions naturally, and how it may respond to 
human activity" that could lead to desertification and the need for 
reforestation.

Eltahir and Hildebrandt, who is now at the UFZ Center for 
Environmental Research, in Leipzig, Germany, said the unusual forest 
is an interesting remnant "of a moist vegetation belt that once 
spread across the Arabian Peninsula" in the distant past. At that 
time the regional climate was generally wetter.

The forested area in the Sultanate of Oman is now semi-arid, and most 
of the ancient tree vegetation is gone. This small remnant has 
managed to survive in the Dhofar Mountains.

But it is under threat.

Although many Omanis have moved into cities and towns as the country 
has grown rich on oil, Eltahir explained, a family's prestige still 
comes from owning many camels, and people now tend to keep more 
camels than they need, which is part of the problem facing the forest.

"It is an unusual place," Eltahir said. "It's a very good example of 
a unique and fragile ecosystem" where constant pressure from 
over-grazing can have consequences beyond defoliation. In fact, the 
forest illustrates how small changes can lead to major impact on far 
bigger systems, Eltahir said.

The trees in wetter ecosystems would likely recover from small 
amounts of over-grazing, Eltahir said, but "in this location, due to 
the nature of the interaction of the canopy structure with the 
clouds, the trees may not recover."

The two said the forest probably would not regenerate naturally once 
it is gone. Without the trees that sweep the extra water from clouds, 
the forest cannot regrow. Grass, even if abundant, cannot collect 
enough moisture from fog to let a forest regrow.

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