| dc.description.abstract | This study investigates the possible impact of deforestation on the climate of Eastern
Africa. The study area is located between approximately longitudes 25 °E to 50 °E and
latitudes 20 "N to 10 "S. The data used in the study comprised monthly rainfall data for
the period 1931 - 2000 obtained from the Kenya Meteorological Department, Nairobi,
Kenya and deforestation scenarios developed by the Integrated Model to Assess the
Global Environment (IMAGE) of the National Institute of Public Health and the
Environment, the Netherlands.
Climate variability over the study region was analyzed using the rainfall data. The quality
and homogeneity of the data was assessed to detect any errors and inconsistencies. Mass
curve analyses were used to test for the homogeneity of the data and the data sets that
satisfied the quality criteria used in the subsequent analyses. Time series analysis was
used to examine the possibility of climate change over the study region through the trend .
and cyclic variations of the seasonal and annual rainfall. Binomial coefficient method was
used to smooth the series and the student t-statistic used to evaluate the statistical
significance of the trends. In order to examine the impact of deforestation on the climate
over the East African region, the ECHAM5 climate model developed at the Max Planck
Institute of Meteorology, Hamburg, was used. The suitability of the climate model for use
over the region was evaluated by examining how well it simulates the regional
climatology. Using scenarios developed by the IMAGE model, two 1O.5-year experiments
were run and the results analyzed differentially; the initial six months for each experiment
were regarded as spin up time and neglected. The first experiment, which constitutes the
reference experiment, used 1995 deforestation scenarios while the second, referred to as
the future simulation, was run using the future (2050) scenarios as obtained from IMAGE.
The boundary conditions were the same for both the experiments.
Significant trends were observed over most of the regions over East Africa. The major
cycles revealed from spectral analysis were 2 - 2.5 years, 3.6 - 4.4 years, 5 years and 10 -
12 years. These results from temporal and spectral analysis suggest a climatic variation
and quasi-periodic variability within the data over the region. The results from the
III
reference experiment of the ECHAM5 climate model showed a fairly good comparison
between the observed and simulated rainfall climatology. The results from IMAGE
vegetation scenarios indicated an increase in the net solar radiation over the western parts
of the study region as a result of the decrease in vegetation, and hence exposure of the
surface to the incoming radiation. Projected evapotranspiration decreased over most of the
western and northern parts of East Africa due to the decreased amount of leaf area index.
Rainfall and cloud cover increased for the future case over the western parts of the study
area which was attributed to increased moisture convergence into those regions. However,
the study projected a decline in rainfall and cloud cover to the east, which was associated
with the decrease in moisture convergence. The increase in rainfall over the western parts
of the study region led to increased runoff over these regions, whereas the converse was
evident towards the eastern parts where declines in rainfall and cloud cover were evident.
The results from this study show that deforestation will have a considerable effect on the
climatic regime of the study region. Since nearly every sector of the economies of the
nations over the study region is affected by weather/climate in one way or the other,
including the water, energy, transport and agriculture sectors, climate alterations will
disrupt the smooth running of the various socio-economic activities in these sectors. The negative impacts are most likely to affect the agricultural production on which the
economies of the countries in Eastern Africa rely. This study provides relevant
information that may be useful in the planning and management of sectoral activities to
mitigate against the adverse effects resulting from climate alterations due to deforestation over Eastern Africa. | en |
