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Tuesday, 31 January 2017

Issues of Eucalyptus Plantations

Photo Credit: Kateregga Dennis
It was estimated that in 1989 world wood consumption was around 4,560 million m3    most of which was from non-sustainable sources.  A projected consumption of 2010 was at 6,860 million m3 which meant further loss of natural tree cover leading to desertification.  There are indigenous species that can be used to control desertification but they are a difficult to establish. Fast growing species like Eucalyptus have been a quick fix, in producing firewood for charcoal reducing the rate at which vegetation is being cleared for firewood. An estimation of 25 million ha of fast growing trees are needed to satisfy the demand for fuel wood in Sub Saharan Africa.

Eucalyptus has been planted indiscriminately, where there is competition for land, water or nutrients that has brought a few problems including; the reduction of natural forests depriving the people of their benefits; it has promoted soil and nutrients loss; it has reduced hydrological values when water resources dry up; it causes biodiversity loss; it is allelopathic to crops. It should be noted that replacing a natural forest ecosystem with eucalyptus will have grave effect on fauna adapted to the previous environment. The Eucalyptus trees grown are often attacked by disease and insects. Chemicals are used which include pesticides, which have killed herbs, shrubs and grasses near or around the trees. These agrochemicals have polluted land and waterways, as a result crops and livestock have been lost. Decomposing Eucalyptus leaf and Pine needles in tree plantations have reduced soil pH.

Research done in Kenya showed that forests carbon sequestering is more in biomass and soil than 50 year old plantations of fast growing species (Cupressus, Pinus and Eucalyptus). An article written by scientists in the Nature Climate Change in 2013 concluded that replacing natural forests with plantations to create sinks for climate change mitigation is false, because you cannot account for the carbon lost from the destroyed natural forest. The underground stems, bulbs and roots store huge amounts of carbon dioxide, but when they die after being deprived of water and light by the tree plantations (Cupressus, Pinus and Eucalyptus) they decompose and release methane which is more potent than carbon dioxide into the atmosphere. Tree plantations have led to sawmill boom, they emit several gases such as Nitrous oxides (NOX), Carbon monoxide (CO), Sulphur oxides (SOx) and volatile organic compounds (VOC).  Polluted water from the sawmills ends up into the soil, surface and ground water. 

By Kateregga Dennis, BA(ECON), Dip.IEL, Consultant

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