The people of Rwanda concluded the “Tree Planting Week” on Saturday 21st November, 2009. The target was that the nation would plant 2,000,000 trees within the week. Tree planting, forestation and reforestation particularly in the politically sensitive encroached Gishwati natural forest where farming communities that had encroached on the natural forest had to be relocated and in many parts of Rwanda demonstrates the nation and government’s concern for the environment and with the establishment of the National Forestry Authority (NAFA) one can only hope that things will get even better.
Tree roots bind soil together, and if the soil is sufficiently shallow they act to keep the soil in place by also binding with underlying bedrock.
Tree removal on steep slopes with shallow soil thus increases the risk of landslides, which can threaten people living nearby.
This was exemplified by the events in Rubavu and Nyabihu districts. The presence or absence of trees can change the quantity of water on the surface, in the soil or groundwater and in the atmosphere.
This in turn changes erosion rates and the availability of water for either ecosystem functions or human services.
Undisturbed forests have very low rates of soil loss estimated at 2 metric tons per square kilometre. Forests are also able to extract carbon dioxide and pollutants from the air, thus contributing to biosphere stability.
Deforestation on the other hand is a contributor to global climate change, and is often cited as one of the major causes of the enhanced greenhouse effects.
Tropical deforestation is responsible for approximately 20% of world greenhouse gas emissions. According to the Intergovernmental Panel on Climate Change (IGPCC) deforestation, mainly in tropical areas, accounts for up to one-third of total Carbon Dioxide emissions.
Trees and other plants remove carbon (in the form of carbon dioxide) from the atmosphere during the process of photosynthesis and release oxygen back into the atmosphere during normal respiration.
Deforestation generally increases rates of soil erosion by increasing the amount of runoff and reducing the protection of the soil from foliage.
Instead of trapping precipitation, which then percolates to groundwater systems, deforested areas become sources of surface water runoff, which moves much faster than subsurface flows.
That quicker transport of surface water can translate into flash flooding and more localized floods than would occur with the forest cover. The water cycle is also affected by deforestation.
Trees extract groundwater through their roots and release it into the atmosphere. When part of a forest is removed, the trees no longer evaporate away this water, resulting in a much drier climate. Deforestation reduces soil cohesion, so that, erosion, flooding and landslides ensue.
Natural forests like Gishwati are particularly vital for the communities that live in its vicinity and humanity at large yet they are most vulnerable to human activities.
They are home to a complex system of living animals ranging from mammals, reptiles and micro-organisms to plant species some of which may be nearing extinction. Up to 90% of West Africa’s coastal rainforests have disappeared since 1900.
In South Asia, about 88% of the rainforests have been lost. In Central America, two-thirds of lowland tropical forests have been turned into pasture since 1950 and 40% of all the rainforests have been lost in the last 40 years.
Some environmental groups argue that one fifth of the world’s tropical rainforest was destroyed between 1960 and 1990, that rainforests 50 years ago covered 14% of the world’s land surface and have been reduced to 6%, and that all tropical forests will be gone by the year 2090.
Damage to forests and other aspects of nature could half living standards for the world’s poor and reduce global GDP by about 7% by 2050, a major report concluded at the Convention on Biological Diversity.
It has been estimated that we are losing 137 plants, animal and insect species every single day due to rainforest deforestation, which equates to 50,000 species a year.
The government could also encourage private investments in forestry resources as is the trend world.
For example Private industry in Brazil has invested $12 billion so far in pulp and paper since 1993 and has recently pledged to invest an extra $14 billion within the sector over the next decade.
The forest products industry accounts for 3% of all global trade accounting for over $200 billion USD per year. Whereas may not have land to support large extensive forests by private the choice of trees planted and utilisation of its products may make the difference.
There were efforts before in Rwanda to plant trees. Travelling by road from Kigali to any party of the country apart from possibly Bugesera one will observe clusters of trees and/or small plantations of eucalyptus (eucalyptus globulus) on hill tops.
Eucalyptus may grow faster, take less acreage with many trees in close proximity, provide good firewood and may not need much effort in terms of crop husbandry but is dangerous to the soil and organisms that may call it home.
Whether those who planted the trees particularly on hilltops knew what the dangers or not, eucalyptus trees are not suitable for areas where crops are grown.
Eucalypts draw a tremendous amount of water from the soil through soil salination in the process of transpiration. Many crops planted in lower areas may lack water and nutrients sacked by eucalyptus leading to lower yields. In fact eucalyptus trees have been planted in some places to lower the water table.
Eucalypts have also been used as a way of reducing malaria by draining the soil in Algeria, Lebanon, Sicily and elsewhere in Europe. Drainage removes swamps which provide a habitat for mosquito larvae, but it is also known to destroy ecologically productive areas.
It also has insect repellent properties and is an active ingredient in some commercial mosquito repellents. This makes it ecologically unfriendly to the many animal and plant species that live in forests.
The trees themselves enhance the loss of grass between trees as it denies life to lower plants by denying them sunlight. The bare canopy areas become highly susceptible to soil erosion.
In the 1850s, Eucalyptus trees were introduced to California and today the US Forest Service is studying how to restore the former ecosystem, and reduce erosion, by removing some eucalyptus trees in selected areas.
In 1894 Emperor Menelik II introduced Eucalyptus trees to Ethiopia to replace the over utilized local trees that were used for wood.
It was later discovered that the “thirst of the Eucalyptus tended to dry up rivers and wells” and in 1913 a proclamation was issued ordering a partial destruction of all standing trees, and their replacement with mulberry trees.
The reforestation efforts of Gishwati natural forest and tree planting in the whole of Rwanda should be towards not replacing trees that were cut but the ecological systems as a whole.
Exotic trees though they may grow faster and show results quickly may not support the necessary ecological and biodiversity of the replanted areas. One hopes that the Rwanda Environment Authority (REMA) and NAFA have had the type of trees planted and their impact on the soils and the general ecosystems in place where they are planted and the long term benefits to local communities.
It may be important to remind those that lead the national tree planting efforts that there are fruit trees. Planting trees that provide food as well as wood and shades for wind breakers and shelter and yet improve our environment and ecology is like shooting two birds with one stone. Families should be encouraged to plant fruit trees that will be a source of food and income.
Many fruit trees such as mango, jackfruits, avocado, pawpaw, guavas etc grow naturally in Rwanda and it might a matter of distributing seedlings to homesteads by creating tree seedlings accessible to them. Over to you, REMA and NAFA.