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http://www.chronicle.co.zw/inside.aspx?sectid=13491&cat=10
Drought, disease threaten baobab tree
By Elliott Siamonga
There are arguably two symbols of Africa — the fish eagle and the baobab tree. Zimbabwe has both in abundance. However, the future of the country’s most grotesque tree, the baobab, hangs in the balance as disease and humans are threatening the survival of one of the most respected and biggest trees in Southern Africa. The worst affected trees are in Matabeleland North and Manicaland provinces.
Communities that directly benefit from the grotesque tree in Beitbridge, Chimanimani and Hwange are already counting the cost, as they can no longer benefit from the bark, which they traditionally used for making mats and other pieces of craft. While the robustness and extreme longevity of these trees imply that they are generally healthy, research carried out recently by the Forestry Commission and Environment Africa’s Tree Africa has revealed that the trees are under threat from the sooty baobab disease. A similar study was done in the late 1980s and established that the disease was a threat to the tree. It appears the problem is continuing.
Sooty is a fungal disease that attacks the tree in the form of what looks like growths on the bark that eventually get colonised by fungi. This blackens and thins the bark, resulting in less supply of water to the branches.
A wilted or shrunken appearance of baobabs, with unusually rough, wrinkled and dull rather than smooth and shining bark, is associated with sootiness; fallen, blackened twigs frequently litter the ground below, severely affecting trees.
Over the past 10 years, large numbers of baobab trees in Zimbabwe have been reported to be dying. The affected trees exhibit a strikingly blackened or burnt appearance. The condition has been referred to locally and abroad as a new disease. Investigations by plant pathologists suggest that although the blackening is caused by growth of a sooty fungus, it is purely a secondary manifestation of a physiological disorder.
The tree, whose botanical name is Adansonia digitata, falls in the Bombacacueae family and has a thick fibrous trunk, which grows up to as much as 25 metres in diameter. In Zimbabwe the tree is commonly found in agro-ecological regions three, four and five in the Zambezi and Limpopo belts.
“Archival evidence shows that exactly the same problem has occurred before and certain trees afflicted earlier this century have since recovered,” noted a recent research document produced by the Forestry Commission and Environment Africa.
It attributed the phenomenon to below average rainfall patterns and the increasingly intensive land use in some communal lands. According to the Forestry Commission, the sooty disease is associated with drought and the lack of biodiversity as contributory factors. Overgrazing in the vicinity of the baobabs exacerbated their water deficit.
“Presently all research that has been carried out point to drought as the major cause of sooty. Previous researchers, as early as 1951, pointed out that there has been alarming loss of baobabs that had died or collapsed through the 1940s,” said a plant ecologist with the Forestry Commission in Harare.
The baobabs were also among the most severely affected trees during the worst drought of 1991/1992. Succeeding droughts have not spared them either. While drought in Africa is sometimes rightly construed as a facile explanation for a wide variety of ills, the fact remains that Zimbabwe’s rainfall over the past decade amounted to the lowest cumulative total.
This is ample evidence that baobabs do not have ample powers of endurance. In some communal lands in Beitbridge and Hwange where human population densities are high while much of the woody vegetation has been removed and the land overused resulting in less herbaceous ground cover, the baobabs have been unable to flourish.
“All sooty baobabs location can be described as arid and latterly have been among the most severely affected by the worst drought in living memory,” said the official with the Forestry Commission.
A sadly familiar picture is seen in some parts of Hwange where human population densities are high, and much of the woody vegetation except giant baobabs has been removed and the land overused resulting in little herbaceous ground cover.
There are clear signs that the communities that benefit from the tree have been affected, as it is used multi purposely as a medicine and source of food by the rural communities in northern and southern parts of Zimbabwe.
The baobab tree is an important food and medicinal source. The leaves can be used as relish in the dry and arid parts of the Zambezi Valley such as Binga. When dissolved in water or milk, the pods of the tree makes a refreshing drink, as it can also be used as a substitute for cream of tartar in baking and also as a fermenting agent in traditional brews.
Medicinally the pulp is consumed to treat fever, diarrhoea and malaria.(continued)
