The big debate over the eucalyptus

And President Kibaki has also urged farmers to grow other kinds of trees that use less water to help conserve the environment. But the Kenya Forest Service says there is no evidence that the eucalyptus, also called the gum or blue gum tree, is to blame for the drying up of rivers and the water crisis that preceded the onset of the short rains last month.

“A lot has been said about what the tree can or cannot do, but no one has come up with sound data to back up the claims,” said David Mbugua, director of the Kenya Forest Service. “The difference in opinion about the effects the tree has on the environment points to a lack of knowledge about the species among Kenyans and a lack of data on the part of government,” he said.

In an article published by the Daily Nation, Wamugunda Geteria, a council member of the Forest Society of Kenya, said those championing the felling of the eucalyptus “are guilty of prescribing the wrong medicine to a sick situation”.

The eucalyptus, a genus native to Australia and of which there are some 700 known species, was introduced into East Africa from Ethiopia in the late 19th century. It was brought to Kenya in 1902 and has been popular ever since due to its fast growth rate. KFS estimates that various species of the tree contribute Sh1.6 billion each year to the economy through products for fuel and building.

“It is impractical to tell Kenyans to cut down the trees that are, to some extent, a source of their livelihoods without giving them an alternative,” Mr Mbugua said. There have been reports that farmers in Murang’a have uprooted the trees with no immediate plans to replace them.

Speaking at the recent Second World Congress of Agroforestry, Nobel Laureate Prof Wangari Maathai called for a ban on the use of exotic tree species, singling out the eucalyptus which she said damages the environment and undermines people’s ability to cope with the effects of climate change.

“Exotic trees, especially eucalyptus,” she said, “have destroyed the biodiversity around them by killing the vegetation and sucking up water.” At the congress, she urged the adoption of native species in the renewed campaign to increase tree cover across the African continent.

She attacked the government for policies which she said encourage the destruction of natural forests and biodiversity zones, replacing them with monoculture tree plantations made up of mostly exotic species grown for commercial purposes. “These plantations are like dead forests because they do not allow other species to grow alongside them,” she said.

But Mr Geteria of the Forestry Society of Kenya says clearing eucalyptus plantations is a simplistic approach to management which may speed deforestation and degradation as Kenyans search for basic forest products. A report by the KFS on the eucalyptus tree faults the assumption that the tree consumes too much water as it grows, leading to the eventual drying up of streams and wetlands. According to the report, the eucalyptus is, in fact, a much more efficient user of water than many other trees.

KFS says studies have established that the tree requires 785 litres of water to produce one kilogramme of wood. To obtain comparable production from a coffee plant, an average of 3,200 litres of water would be needed. But KFS acknowledges that it is not wise to plant the tree in areas that receive less than 1,200 mm of water each year. The same goes for marshlands and land along rivers or large water bodies. Experts argue that a ban on eucalyptus trees would have a negative impact on personal income.