Paris - The world's most popular coffees may be under threat from the decline of highland rainforests in Ethiopia, the arabica plant's only gene bank in the wild, New Scientist says.
Ninety percent of coffee drunk in the world comes from the arabica plant, grown on large plantations in producer countries.
These bushes have very little genetic variety - they have been cultivated from a small handful of individual plants.
That spells vulnerability when disease or pests choose to strike, such as a blight called coffee rust that devastated Brazilian farms in the 1970s.
At such moments, New Scientist says, growers turn to help from Ethiopia, which has arabica bushes growing in the wild, offering a wide range of genetic defences against the disease.
The problem, however, is that arabica's home may soon disappear.
Only several remnants, totalling less than 2 000 square kilometres of south-west Ethiopia's upland rainforest survive.
They have been ravaged by 30 years of woodcutting and razed to make way for tea plantations and resettle people displaced by a drought that struck the north of the country in the 1980s.
"The forest fragments possess enormous variability of arabica coffee. They are the best available source of germ plasm for the crop's improvement and pest control," Ethiopian ecologist Tadesse Gole told the British weekly.
Government plans to protect the last three remnants have foundered because of a lack of cash, he said.
Ethiopia is also the home of the world's largest coffee seed bank, located at Jimma.
However, seed quality declines in cold stores and coffee genes can only be saved effectively by planting bushes in fields. In addition, a far greater genetic reserve is found in the forests, where arabica bushes make up much of the undergrowth. - Sapa-AFP