3.2.3. IMPORTANCE OF FOREST
Forest and other areas covered by trees play a great role in
the survival of human population; being suppliers of shelters and food for
individuals and animals, water, medicinal plants, construction materials and
fuels (PNUE, 2002:130).
26
Table 3: Main hydrographic networks draining in the
mountainous forests(Runyinya, 1982).
|
Forest
|
Congo basin rivers
|
Nile basin rivers
|
|
Gishwati
|
Nkora Cyimbiri Pfunda Sebeya Bikore
|
Satinskyi Giciye
Nyamukingoro
|
Source: Runyinya, 1982
This table shows the role of forests on the environment and on
rainfall. In this forest some rivers flow to Congo basin via Lake Kivu and
others to Nile Basin via Nyabarongo River.
Forests regulate equally the quality of the soil and water, in
protecting the soil against erosion and contributing to their fertility, in
intercepting rainfall they canalize the flow of water.
In Rwanda, 70% of cultivated land and 60% of pasture land were
threatened by erosion because the slopes are over 5%for cultivated land and 10
% for pasture land (ONAPO, 1982:150).
By the fact of its position in latitude, Rwanda is located in
the equatorial domain. A combination of tropical location and high altitude
ensures that most of Rwanda has a temperate year-round climate
The occidental regions where localized Gishwati forest, are
more arose with a mean of 1800mm of rainfall per year. These high
precipitations expose the land of these regions to the erosion (Hitimana,
2006:15)
3.2.4. SPATIAL EVOLUTION OF GISHWATI
Being attacked by different land uses, Gishwati forest has
became gradually reduced at a rapid pace as shown by the figure below.
27
30000 25000
20000 15000 10000 5000 0
Source: Field survey, author, 2012
Figure 6.Spatial evolution of Gishwati
(ha)
1970 1980 1990 1996 2000 2010
3.2.3. ENVIRONMENTAL IMPACTS
Deforestation is one of the major causes of the enhanced
greenhouse effect. Trees and other plants remove carbon (in the form of carbon
dioxide) from the atmosphere during the process of photosynthesis. Both the
decay and burning of wood release this stored carbon back to the atmosphere. It
can cause the destruction of the habitats that support the biological diversity
thus causing population shifts and extinction. Deforestation generally
increases rates of soil erosion, by increasing the amount of runoff and
reducing the protection of the soil from tree litter.
Forestry operations themselves also increase erosion through
the development of roads and the use of mechanized equipment. Deforestation can
be accompanied by some degree, the gradual reduction of water resources by
deforested region; desertification is an extreme result. Forests support
considerable Biodiversity.
Deforestation percolates into the soil where deforested areas
become sources of surface water runoff, increasing potential for flooding.
Removal of trees does not always increase erosion rates. In
certain regions shrubs and trees have been encroaching on grassland. The trees
themselves enhance the loss of grass between tree
28
canopies. The bare inter canopy areas become highly erodible.
MINIRENA is studying how to restore the former ecosystem and reduce erosion by
planting the trees.
Tree roots bind soil together and act to keep the soil in place.
Tree removal on steep slopes increases the risk of landslides.
All population around Gishwati natural forest has not got a land
parcel in the forest as it is indicated in the following table.
Table 3.The year of land parcel
holding
|
Period
|
Number of respondents
|
%
|
|
Before1994
|
11
|
18.3
|
|
After 1994
|
14
|
23.3
|
|
No parcel
|
35
|
58.3
|
|
Total
|
60
|
100
|
Source: Field survey, author,
2012
Among 25 interviewees with parcel in the forest, 18.3% got the
land before 1994 and 23.3% after 1994 and these are 41.6%of the total
interviewed people. Other 58.3% do not have parcels in the forest but among
them, some use the forest illegally. So the forest has been degraded before and
after 1994 but before 1994 the degradation was not significant as the table
shows. Among 25 with parcels in the forest about 44% got the parcels before
1994 and this shows that the forest began to be threatened before 1994. The 56%
remains have allocated the parcel just after 1994 and the majority of them were
returnees from DRC.
Among 60 interviewees about 53% accepted that the forest has
gradually reduced by the occupation and farming of this before and after 1994
and this resulted into different impacts on environment and socio economic
conditions of the surrounding population.
So the major effects highlighted are shown in the following
table.
29
Table 4 .Most effects on the
environment
|
Answers
|
Effective
|
%
|
|
Landslides
|
23
|
38
|
|
Erosion and flooding
|
17
|
28.3
|
|
Property losses
|
8
|
13.3
|
|
Increase in water salinity
|
12
|
20
|
|
Total
|
60
|
100
|
Source: Field survey, author,
2012
All these factors combined has led to the decline production
of agriculture but also the
availability of other use of water such as hydro electrical
power and domestic use of water and the relevant prove was the flooding in the
Bitenga wetland. It was observed that the district of
Nyabihu is also experiencing significant impacts especially in
Jomba sector whereby the last rainy season 7 persons dead,153 families have
lost their properties and 385 houses have been destroyed according to the
executive secretary of the sector.
After analyzing these results, we concluded that the set of
these impacts has led to the decline of the internal national economy in
general and on the surrounding regions in particular as they carried on the
soil such as:
? Loss in soil fertility for agriculture and grazing
? Loss of forest products
? Gulling
By these results we concluded that the second hypothesis which
states that Local population is being affected by soil erosion and flooding
resulting from the forest changes is confirmed.
| 
