Abstract:
Land use/ land cover change causes unprecedented changes on the surrounding environment at
different spatial and temporal scales. Muga watershed of the Abbay River Basin is characterized
by deterioration with mismanagement of natural resources. Thus, this study was aimed at detecting
the magnitude and pattern of land use/land cover changes and assessing drivers of changes over
the last three decades (1985 to 2017) in the Muga watershed. Synergy of Landsat imageries (1985,
2002, and 2017), household survey, focus group discussion, key informant interview and field
observation were used to detect changes and drivers of changes. Land use/land cover changes in
the study watershed were detected using digital image analysis techniques, and their socioeconomic
and
biophysical
drivers
were
analyzed
using
descriptive
statistics.
The
change
detection
results
exhibited a significant increasing trend of cultivated land and urban areas by 12 and
270%, respectively, from 1985 to 2017. In contrast, grasslands, forest lands, and shrub-bushlands
showed a declining trend of about 40, 21 and 12%, respectively. The results from the household
survey showed that the expansion of cultivated land, cutting of trees for fuelwood and construction
purposes, population growth, land tenure policy and climate variability were the most influential
drivers of land use/ land cover changes in the study watershed. Thus, alternative sources of income
for youths and landless peasants and integrated watershed management, which has paramount
importance in maintaining economic and ecological benefits were suggested to alleviate the
adverse effects of LULC changes in Muga watershed.
Soil erosion is one of the major threats in the Ethiopian highlands. In this study, soil erosion in
the Muga watershed of the Abbay River Basin under historical and future climate and land use/
land cover (LULC) change was assessed. Future LULC was predicted based on LULC map of
1985, 2002, and 2017. LULC maps of the historical periods were delineated from Landsat images,
and future LULC was predicted using the CA-Markov chain model. Precipitation for the future
period was projected from six regional circulation models. The RUSLE model was used to estimate
the current and future soil erosion rate in Muga watershed. The results of the study show that the
average annual rate of soil erosion in the Muga watershed was increased from approximately 15
t ha
-1
year
-1
in 1985 to 19 t ha
-1
year
-1
in 2002 and 19.7 t ha
-1
year
-1
in 2017. If a proper measure
against the LULC changes is not taken, the soil loss rate is expected to increase and reach about
20.7 t h
-1
yr
-1
in 2033. The results of the study also show that in the 2050s, soil erosion is projected
to increase by 9.6% and 11.3% under RCP4.5 and RCP8.5, respectively compared with the
baseline period. When both LULC and climate changes act together, the mean annual soil loss
rate shows a rise of 13.2% and 15.7% in the future under RCP4.5 and RCP8.5, respectively, which
is due to synergistic effects. The results of this study can be useful for formulating proper land use
planning and investments to mitigate the adverse effect of LULC and climate change on soil loss.
The study also demonstrated the importance of an integrated approach, assessing the combined
impacts of LULC and climate change, for accurate estimation of soil losses.