The Eucalyptus Problem

The Eucalyptus Problem

On the Entoto mountain and many other places around Addis Ababa, the existing vegetation is Eucalyptus globulus. This is an Australian tree brought to Ethiopia some 100 years ago. At this past time, most of the area around the town had been deforested due to the need for wood construction and fuel.

The introduction of the new species was very successful, as its speed of growing surpassed the indigenous trees. Some of the Eucalyptus on Entoto have their origin in that first phase of reforestation, but plantations continued during the last century.

At present, the bulk of the Park area is covered by eucalyptus plantations. The new species is an integral part of the Ethiopian history, but at the same time, it is a tree that not belongs to the Ethiopian flora.

Biodiversity:  Foreign trees often have difficulties in adjusting to their new environment. The Eucalyptus is growing apparently without trouble, but it is not capable of sexually reproducing itself, i.e. the seeds do not germinate in the Ethiopian soils. Therefore the standard procedure of introduction is the planting of seedlings.

The young trees soon start to compete very efficiently with other vegetation. It is a fast grower, easily reaching above other trees and suppressing them. At the same time, a chemical component in the leaves and roots prevents the growth of both other trees and herbs. This leads to a monoculture with Eucalyptus as the only tree species and eventually no ground cover at all.

The Eucalyptus demands large quantities of water. Areas which earlier were periodically wet and with a flora adjusted to such conditions, get drained by planted Eucalyptus. Because of the poor flora and the lack of plants needed by specialized insect and birds, the biodiversity of a eucalyptus plantation is extremely low. Also, when timber is continuously being taken out of the area without no input of fertilizer, the soil quality gradually decreases, reducing the possibilities of the reintroduction of indigenous species.

The Importance of Domestic Roots Against Erosion.

The Torrential Rains and Erosion

Erosion: Because there is no ground cover, the only thing to hold the soil is the web of roots of the trees. The soil-holding capacity of Eucalyptus is very moderate compared with the trees initially covering the slopes of Entoto. This causes severe erosion, easily observed in the water running through Addis in connection with the rainy seasons. For every rain period, the layer of fertile soil gets thinner. If nothing is done now, in a couple of years, there will be nothing left for new vegetation, and the erosion will be irreversible.

Flooding:  On Entoto, every leaf and every branch have fallen to the ground is collected by people, whereas in a natural forest, organic material from leaves, wood, roots etc. is left to be decomposed in the soil. The organic matter improves the soil structure, leading to a higher infiltration rate and a much better water-storage capacity.

Even if the Eucalyptus is a tree with very high water consumption, the total amount of water taken up by the vegetation is probably higher in a juniper forest, as the total biomass is more significant abundant. The entire surface of leaves, needles, branches etc. should also be much larger, with increasing the amount of precipitation returned to the atmosphere by evaporation.

As the water catchment of the eucalyptus plantation is very low, it cannot counterbalance the uneven distribution of rain. The result is flooding in the downslope areas, in this case, the northern district of Addis. In August 1994, three people were drowned because of such flooding.

Land Use: The bulk of the area is used as a plantation. Eucalyptus has been grown for a long time, mainly for the production of construction wood. Fallen branches for fuelwood are collected by people living in the area, as well as outsiders.
 Some females are actually sweeping the ground for some single twigs. Lately, the illegal cutting of trees has accelerated, large amounts of timber being brought out.

The regular land use on this kind of soil would be cattle raising and mixed farming (Foth 1984), and this can still be seen to some extent. One part in the upper eastern part and another in the western is used for crops and cattle breeding.

Where the Eucalyptus has not yet ruined the ground vegetation cover, sheep are brought for grazing. There are fenced pastures for the animals, but instead, they are guarded by shepherds. Inside the proposed park area there are about 60 households.

Already today, visitors come to Entoto for recreation purposes, as it is the only forest-like area in the vicinity of the city, and because of the beautiful views from the mountain.

The Australian Eucalyptus Tree and its Ancient Legacy.

  • It seems very strange that a tree species can be hostile and directly toxic to its surrounding nature this to the extent that it eliminates the very soil layer that forms its basis and thus undermines the conditions for its future as a species.

  • The reason for these strange hostile contradictions of this Australian tree's unique touch on its environment has its explanation in the unique autonomous surviving strategi of the eucalyptus tree. The background here is the eucalyptus tree's artificial relocation and its introduced foreign export location into the Ethiopian highlands. Furthermore derives the description of this matter from the original continental remoteness of the eucalyptus tree's geological and genetic past within Australia.
    • The distant continent of Australia's developed fauna and flora has undergone an extremely long evolutionary optimization to best adapt to the unique condition of its geological and surrounding genetical characteristics.  The Australian truly uniquely native indigenous habitat received through this remoteness its distinctive property of plant and wildlife. This remote location deeply selected the specificity of its soil and in this even its microbiological uniqueness.

        • In Australia, its unique flora and fauna have, through separate seclusion from other continents developed its distinctive character to become more or less toxic to its environment. However and very important in this context, Australia's organisms have in their defence system developed an equally strong resistance against these multi-folded toxicities that can be described as a type of evolutionary competition-oriented circumstances on their continent.  Furthermore, this toxicity depends on direct genetically controlled survival strategies to avoid, for example, overgrazing or a large infestation of insects or even as a tool in the competition between tree species of the ground itself.

            • The Australian continent and its eucalyptus tree are displaced due to continental distances of oceans to other continents. It has thus in Australia been possible to develop animal and plant species that have no direct genetic contact with the animals and vegetation of other continents.  An extraordinarily long time appear here in segregated genetic enhancement for Australia's separate evolution regarding its organisms' optimization of plants' toxicity. This pre-historic evolution in the genetic legacy of the very remote past in the Australian surrounding fauna and flora is unique but still mostly beyond knowledge within nature's own ancestral vault. This genetic material is something to carefully, scientifically protect and seriously investigate because it may include invaluable components of medicine or other completely invaluable research.
            • Thus, the development of this tree's toxic substances has given the eucalyptus tree increased survivability in an often very demanding environment. The eucalyptus tree's toxicity is controlled by its DNA and provide the tree with protection from overgrazing animals. However, it's possible, the tree also improved capacity regarding the struggle of water and nutrients with other tree species. The contact with the toxicity of eucalyptus tree caused the biotope of Australia to pass through aeons of improved resistance. With an evolutionarily tempered competition due to an often fierce struggle for both nutrition and water resources, the Australian vegetation received the legacy of unique genetic defences and sufficient toxic protective defence against various herbivores. 

            • The Australian eucalyptus trees are therefore optimized for the Australian continent where they have their genetic origin but at the same time potentially directly harmful to habitats on the other continents.  The geographical distance between Australia and other continents are large enough to deeply create a different DNA and for other continents biotopes and dangerous due to weak defence mechanisms among other continents' biotopes against the toxicity of the eucalyptus tree's biology. This considerable distance often leads to very different ecology of the other continents and causes to expose the essential lack of sophisticated defence or resistance within their own native organisms' genetic constitution. 

            • The introduction of this Australian tree into Ethiopia over a hundred years ago, inflicted this contradictions and problems since it was not enough advanced knowledge internationally in the natural sciences to enable an insight into the danger with the exotic and alien introduction of plants or animals. Thus, by severe short-sightedness due to lack of international science in ecology, this eucalyptus tree was introduced to the Ethiopian highlands. Nor ruled yet for a long time the knowledge internationally about the necessary laboratory examination of plants' and animals' toxicity regarding the necessity of rigorous inspections in epidemic secured vaults, sealed by government-supervised laboratory environments before allowing any international dissemination. 

            Indigenous species

            There is also an area in southeast containing junipers, but these are facing a significant threat from fuelwood collectors. On the steep hillsides and in the gorges and gullies in the lower part, there still remain trees of indigenous species like Juniperus procera, Podocarpus gracilior, Dovyalis abyssinica, Olea europea var, Africana, and Ficus sp.

            A few solitary indigenous trees stand in open areas, e.g. Hagenia abyssinica and Hypericum sp. In the upper eastern part, there are beautiful meadows with a high diversity of herbs, and several species can also be found along the brooks. 
            (Håkan Blanck and Pia Englund, Entoto Natural Park 1995).

            Although regarding the eucalyptus plantation in Ethiopia, this tree follows by very high water consumption,  and this while the total water amount of water taken not deliver enough of this water to the surroundings or deep aquifers and then regarding the specific Ethiopian biotope. The Australian Eucalyptus requires this water for its secondary survival strategy but a foreign organism to the Ethiopian highland, within an incompatible evolutionary soil and type of nature. This eucalyptus tree uses this water to its biomass but regarding the Ethiopian biotope not effectively distributing this water to the environment and neither to Ethiopia's natural groundwater reservoirs.  In Ethiopia, this eucalyptus tree is incompatible to the type of biotope in the planted surroundings, which furthermore is very scientifically evident and contrary to the distinctly higher level of soil accumulated and distributed water of the native Juniper forest. This phenomenon of naturally accumulated water occurs in the indigenous Juniper forest thanks to this native tree's effect of securing healthy topsoil and web of strengthening undergrowth.




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