Post on 03-Apr-2018
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Rapport/Report
NTNU
Norgesteknisk-naturvitenskapelige
universitet
Fakultetorsamunnsvitenskapog
teknologiledelse
Geografskinstitutt
Daniel Ayalew Mengistu
Remote sensing and gis-basedLand use and land cover change
detection in the upper Dijo river
catchment, Silte zone, southern
Ethiopia
Working papers on population and landuse change in central Ethiopia, nr. 17
Acta Geographica-Trondheim
Serie A, Nr. 23Series A, No. 23
Avhandlinger og rapporter/Theses and reports2008
I n n o v a t i o n a n d C r e a t i v i t y
Addis Ababa
University
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REMOTE SENSING AND GIS-BASEDLAND USE AND LAND COVER CHANGE DETECTION
IN THE UPPER DIJ O RIVER CATCHMENT,SILTE ZONE, SOUTHERN ETHIOPIA
DANIEL AYALEW MENGISTU
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ABSTRACT
Land use and land cover (LULC) change is one of the challenges which strongly influence the process
of agricultural development and the food security situation in Ethiopia in general and in the Upper Dijo
River catchment in particular. Remote sensing and geographic information systems (GIS) are important
for the monitoring, modelling and mapping of land use and land cover changes across a range of spatial
and temporal scales, in order to assess the extent, direction, causes, and effects of the changes. The
changes in land use and land cover which occurred between 1972 and 2004 in the Upper Dijo Rivercatchment, located in the middle Rift Valley system of Ethiopia, were monitored using such advanced
spatial technologies, supplemented by field verification. The study area covered 55.7 km2, and had
previously undergone substantial land use and land cover changes, mainly due to high population
pressure.
The main objective of the study was to assess and evaluate the extent and direction of changes in LULC
in the Upper Dijo River catchment, to explain the changes and identify some of their effects on both the
livelihoods of the local people and the local environment, and also to explore some of the conservation
measures designed to overcome problems associated with land use and land cover changes. Aerial
photographs taken in 1972, an EROS-1 satellite image from late 2004 and also geographic information
system (GIS) techniques were used to monitor the changes and to generate maps of the LULC of the
area in these periods. Information on the socio-economic conditions of 120 selected households and the
results of tests on soil samples taken from a depth of 30 cm at four different land use sites were used to
identify the underlying factors and explain the effects of LULC changes.
Observations showed that in the 32-year period between 1972 and 2004 shrub-grassland and riverine
trees covers had decreased at a rate of 21.5 and 16.3 ha per year respectively. Riverine trees suffered the
greatest devastation and by 2004 had been reduced to only 16% of their cover in 1972. In contrast,
eucalyptus tree plantations, annual crops and bare land/open grassland cover increased at a rate of 2.8,
12.5 and 24.8 ha per year, respectively. Correspondingly, bare land/open grassland increased by
344.5% at the expense of shrinking shrub grasslands, and have expanded in uninhabited areas.
Growing population pressure and its associated problems, such as the increasing demand for land and
trees, poor institutional and socio-economic settings, and also unfavourable government policies, such
as lack of land tenure security and poor infrastructure development, have been the major driving forces
behind the LULC changes. Hence, special attention should be given to the introduction of wise land
resource uses and management practices, secure land possession systems, regulated population growth,
and integrated environmental rehabilitation programmes. The existing tree plantation practices shouldbe encouraged by promoting the planting of indigenous tree species, rather than eucalyptus trees, in
order to enhance ecological harmony.
Keywords: Ethiopia, GIS, land use changes, land cover changes, population pressure, remote sensing
Acknowledgements: The study was supported by the NUFU-funded research and collaborationprogramme Population growth and land use changes in Central Ethiopia.
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INTRODUCTION
Land is the platform on which most human activities are performed and is the source of many
of materials needed for such activities. It is the most important natural resource for countries
such as Ethiopia, where the economy depends greatly upon the agricultural sector.
Developments in testing methods and differing abilities to use land resources often give rise to
changes in land use and land cover(LULC). At times such changes have beneficial while at
other times they have had detrimental and adverse impacts on the environment and peoples
livelihoods (Briassoulis 2000).
Research conducted in Ethiopia has shown that there were considerable LULC changes in the
country during the second half of the 20th century (Solomon 1994; Woien 1995; Gete 1997;
Crummey 1998; Kebrom & Hedlund 2000; Rembold et al. 2000; Belay 2002; Woldeamlak
2002; Muluneh 2003; see also Muluneh, unpublished data 19941). Most of these studies
indicated that deforestation and encroachment of cultivation into marginal areas were the majorcauses of land degradation, particularly in the highland part of the country. For instance, Gete
(1997) and Belay (2002) reported a serious trend in land degradation resulting from the
expansion of cultivated land at the expense of forestlands in Dembecha in north-western
Ethiopia and in the Derekoli watershed in South Wollo. Kebrom & Hedlund (2000) also
reported an increase in open grazing areas developing at the expense of shrublands and forests
in the Kalu area, north-central Ethiopia. Rotational LULC involving cultivation and vegetation
(forest and bush) was practised in the Metu area of south-western Ethiopia (Solomon 1994). In
contrast, Muluneh (2003; and unpublished data 1994) and Woldeamlak (2002) have reported
an increase in wood lots (eucalyptus tree plantations) and cultivated land at the expense of
grazing land in both Sebat-bet Gurage land in south-central Ethiopia, and in the Chemoga
River watershed in north-western Ethiopia. These reports have shown heterogeneity in the
changes in type, pattern, direction, and magnitude of LULC in the country and have revealed
the difficulty of extrapolating the known trends to areas that have not been surveyed.
1W.Muluneh (1994) Population pressure, land use change and patterns of agricultural productivity in Ezan-
Wollen and Cheha Weredas Sabat-bet Guragheland. Unpublished MA thesis, Department of Geography, AddisAbaba University, Addis Ababa.
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Hence, region-specific information of such changes in LULC is essential for land use planning
aiming at wise resource management and to maximize the productivity of both agricultural and
non-agricultural land at both regional and national levels. However, in Ethiopia information on
these changes is either lacking or unavailable for many small areas of land, for which it is
extremely difficult to make generalizations or doing so might lead to erroneous conclusions.
Many of the aforementioned studies were conducted in the northern-central highlands of the
country. The exceptions are those by Muluneh (2003; and unpublished data, 1994), Solomon
(1994) and Rembold et al. (2000). Rembold et al.s (2000) study, in particular, is probably the
only one to have been carried out in the Rift Valley area. This implies there is a gap in terms of
spatial representation in land use and land cover change studies in the country. In order to fill
this gap, the present study was carried out in the upper part of Dijo River catchment in Silte
Zone, SNNPR,2 Ethiopia. The aim of the study was to address the issues of LULC changes in
general, and in order to evaluate the magnitude and direction of the changes the aim was to
determine whether or not the changes are favourable, and to identify the forces working behindthe changes and the ensuing effects on the livelihood of the people and their environment.
The study was carried out using aerial photographs taken in 1972 and enlarged to a scale of
1:12000, a 1.8 m resolution panchromatic EROS satellite image taken in 2004, and also
geographic information systems (GIS) in conjunction with conventional techniques. Unlike
most of the aforementioned studies, this paper is the result of a detailed, large-scale analysis of
LULC changes in a small river catchment.
The study area, the Upper Dijo River catchment, was selected for research mainly because it
had previously undergone substantial land use and land cover changes, its magnitude was open
for in-depth study, it was subject to high population pressure, the interaction between land use
and population was complex, and it comprised a variety of physiographic features.
STUDY OBJECTIVES
2
Southern Nations and Nationalities Peoples Region (SNNPR) is one of the major national regions found in thesouthern part of Ethiopia (Fig. 1).
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The main objective of the study was to assess and evaluate the extent and direction of changes
in the LULC of the Upper Dijo River catchment and to explain the changes and identify some
of the effects of the changes on both the livelihoods of the people and the local environment,
and also to explore some of the conservation measures practised by local people to overcome
problems associated with land use and land cover changes in the area. Specifically, the aim of
the study was to: (i) identify and map the extent of LULC changes over a period of three
decades; (ii) investigate the proximate and underlying causes of LULC changes and their
subsequent impacts on the environment and livelihoods of the people; and (iii) examine
farmers responses to the impacts of LULC changes in the area.
STUDY AREA BACKGROUND
Location and size: The study area, in the newly structured Silte Zone, SNNPR, is located 164
km south of Addis Ababa, between 751N 759N and 3812E 3815E, and has a total
area of 55.7 km
2
(Fig. 1). It forms the western portion of the Shalla Lake drainage system,which in turn is part of the main Ethiopian Rift Valley system.
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Figure: 1
Location map of the study area: the Upper Dijo River catchment.
Physiology, geology and soils: The Upper Dijo River catchment, located on the western edge
of the main Ethiopian Rift Valley escarpment, is characterized by partly swelling and generally
undulating surface features in its central part but has almost flat topography in southern reaches
toward the Ethiopian Rift Valley floor, and is bordered by steep slopes toward the escarpment
on its northern side. The elevation falls from about 2900 to.2000 masl. The area is dissected
by several small streams that rise from the eastern edge of the Shewan Plateau and western
escarpment side. In addition, the topography of the area is highly influenced by structural
faults.
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The landscape has undergone a series of geomorphic processes. However, the evolution of
present-day landscape features is generally attributed to recent geological events of Tertiary
and Quaternary volcanic episodes and tectonic activity that occurred during the Upper
Pleistocene and beginning of the Holocene epochs and also between the late Quaternary and
the present. In addition, faulting occurred during and after these epochs and the subsequent
degradation processes have been responsible for reshaping the landforms of the study area.
Also, minor faults aligned NNESSW have led to the formation of very steep sloping land on
the back slope of the study area. These faults are down-thrown and have resulted in the
submergence of the lands on the sloping sides of the fault lines. The major faults passing
though the middle of the study area are partly responsible for the overall appearance of the
landscape in general and the study area in particular (Fig. 1).
With regard to the geology, the area is generally volcanic terrain which has been affected by
volcanism since the Pliocene and Quaternary periods, resulting in fissures and conical
eruptions (Sagri & Getahun 1998). The whole area is covered by a huge volume of silicic
pyroclastic materials and scoria cones. They are mainly per-alkaline rhyolitic ignimbrites
interlayered with basalt and tuffs (Di Paola 1972 quoted in Sagri & Getahun 1998). These
volcanic materials are either in situ or have been reworked by different geomorphic agents. In
general, the geology of the area consists of Tertiary intermediate to basic volcanites resting on
Mesozoic sediments and Precambrian basements.
On the basis of the information obtained from field survey and the results of laboratory
analyses, six major soil units were identified: Haplic Phaeozems, Luvic Phaeozems, Chromic
Cambisols, Rhodic Nitosols, Haplic Nitosols, and Eutric Vertisols (Abyiot 20053).
Vegetation and climate: The original vegetation type of the study area was woodland savanna
(Zemede 1998). It comprised a type of woodland and savanna vegetation where scattered trees
3 Abyiot Legesse was one of the four members of a research team who surveyed the problem of soil degradation
under the auspices of a NUFU research project run by the Department of Geography & Environmental Studiesat Addis Ababa University (AAU) in collaboration with the Department of Geography at NTNU, Trondheim.
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and shrubs occurred in herbaceous elements. Today, due to deforestation, the remnants of these
original vegetation types, particularly trees and shrub woods, are found in small patches only
around mosques and on the steeper slopes of the escarpment, and also along stream courses as
riverine trees. Exotic trees, specifically varieties of eucalyptus trees, are planted extensively
around settlements and along river courses.
According to the traditional agro-climatic zonation, which is based on rainfall, temperature and
altitude, the area that lies above 2400 m and accounts for about 40% of the total area falls
within dry dega agro-climatic zone, while the remaining 60% that has elevation between 2000
and 2400 m lies within the woina dega agro-climatic zone. The former is similar to a warm
temperate climate while the latter is more like a subtropical climate. The area has a mean
annual temperature of 18C and a mean annual rainfall of 1319 mm.
Population and settlement pattern: In 1972 the number of inhabitants of the area wasestimated by counting peasant tukuls4from an existing 1:50,000 topographic map of the area
compiled from aerial photographs taken in the same year. 5 The total number oftukulswas then
multiplied by 4.5 and the average rural household size of Shewa Province between 1968 and
1972 (CSA 1974 cited in Kahsay, unpublished data 20046). Accordingly, the population of the
Upper Dijo River catchment in 1972 was estimated to be 5792. The counting oftukulsfrom the
EROS satellite image taken in 2004 showed that there were 2535 houses. The household
survey conducted in 2004 showed that the average household in the study area consisted of
7.75 persons. Hence, the population of the Upper Dijo River catchment was estimated to be
19,646 in 2004. This shows that population of the area had increased more than threefold over
the previous three decades, with an average annual growth rate of 3.89%. This in turn created
new demands for additional space, food and other resources. As a result of such unprecedented
increases in population size, the pressure on existing natural resources is expected to intensify
in the area. Settlements in the area are predominantly rural and villages are generally linear in
4 farmhouse5After counting the number of dots representing peasant tukuls, the number oftukulswas multiplied by the average
household size at that time.6 B. Kahsay (2004) Land use/cover changes in Central Ethiopia: The case of Yerer Mountain & its
surroundings. Unpublished MA thesis, Department of Environmental Science, Addis Ababa University, AddisAbaba, Ethiopia.
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form. The local residents have access to road transport and there are also schools (two primary
schools and one secondary school), one health centre and two health posts. There are two
towns: Werabe, the seat of Zone level administration, and Alkeso, which is a small market
place located within the river basin.
Land use pattern: The land use pattern in the study area is similar to that of other areas where
enset (false banana) is cultivated, whereby farmers divide their lands into several plots for
different purposes such as for settlement and avenues, growing enset, chat and other cereals,
grazing, and tree plantations. Homestead plots are used for growing the most important crops
such as enset, chat and vegetables. Distant farms are used for growing annual crops such as
wheat, barley, teff, maize, sorghum, and beans. Land plots located outside the inner ring, the
land which is used forenset plantation and annual crops, and at some distance, and which are
marginally important, are used for livestock grazing and eucalyptus tree plantations. There are
also random areas of degraded grounds.
DATA SOURCES AND METHODS OF DATA COLL ECTION
Aerial photographs taken in December 1972 and a satellite image taken in December 2004
were the major source of data used to detect changes in the LULC in the area. The aerial
photographs and satellite image were obtained from the Ethiopian Mapping Authority (EMA)
and ImageSat International, Israel, respectively. The aerial photographs were at a scale of
1:12,500 and were enlarged from a scale of 1:50,000 after mosaicing, georeferencing and
rectification using photogrammetric techniques. The EROS-17
image had a radiometrically
corrected spatial resolution of 1.8 m. Aerial photos were the only source of spatial data in
image form for the period prior to when satellites were launched, while the satellite image was
used because there were no recent aerial photographs available for comparison with older
photographs. Thus, in order to detect and monitor the extent and direction of the changes in the
LULC, it was necessary to compare the aerial photographs of 1972 with the satellite image of
2004.
7EROS A High-Resolution Satellite Imagery. 2004.SAF 1-E 1222411. ImageSat International, Israel.
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LULC change reflects both the biophysical conditions and the history of the socio-economic
setting of a given area. Hence, a household survey was conducted to acquire data relating to the
socio-economic and demographic conditions of rural households which would help to explain
the changes observed in the LULC. First, a sub-catchment area was selected within the Dijo
River catchment, covering an area of c.600 km2 and comprising parts of three weredas
(districts): Silte, Dalocha and Aricho Weriro. In addition, there wee 31 kebele peasant
administrations (KPAs). The Upper Dijo River catchment, the sub-catchment area selected for
this study, was systematically delineated from a 1:50,000 topographic map of the area. The
selection of the study area took into consideration the relative location, drainage density and
topographic situations, soil degradation, agro-climatic conditions, settlement patterns and
access to road transport systems, and other basic infrastructure.
The Upper Dijo River catchment consists of parts of two KPAs: Anshebeso and Arat Ber. To
select 120 sample households, which accounted for approximately 5% of 2535 households ofthe two sample KPAs, four parallel transects were drawn (arrayed) at 200 m altitude intervals.
Sample quadrants (average size 300 m2) were set over each transect. Each transect had a
number of quadrants relative to its population density. Each quadrant contained a number of
households. Depending upon the number of households within the quadrants, sample
households were randomly selected using a lottery method.
Structured questionnaires were administered to the sample household heads. The
questionnaires included several issues relating to demographic situation, landholding size,
livestock and crops, soil fertility management, and off-farm and non-farm employment. The
questionnaires were pre-tested and modified in the field. Moreover, the soil sample results of
one of the members of a research team was chosen to evaluate the effect of LULC changes on
the soils, and the results of a soil survey and analysis made by Aby iot (2005). In addition, 10
soil samples were taken for analysis from pocket areas (areas with relatively little human
influence such as religious places and farm boundaries) where LULC changes were minimal
and which had not been subject to much disturbance in their history, such as sacred areas (e.g.
mosque compounds), remnants of natural vegetation and farm boundaries. The samples were
taken from 30 cm deep auger holes along the transects. This approach substitutes space for
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time and is referred to as a spatial analogue method (Woldeamlak & Stroosnijder 2003, 37). In
this regard, variations in soil properties are attributed to the observed differences in the LULC.
Some of the research findings made by Shiferaw Teka 8 were used to compare the implications
of LULC changes on the biodiversity of the area.
To evaluate changes in the LULC, data from both aerial photographs and the satellite image
were systematically processed, involving georeferencing, mosaicing, interpretation,
digitization, and mapping. The aerial photographs were first scanned, georeferenced in UTM
projection using control points collected in the field, and mosaiced after rectification using
photogrammetric techniques. Georeferencing of the EROS-1 image was made in the same
projection as the aerial photographs, using the selected ground control points (GCPs). Then,
the interpretation and LULC classification process was performed by establishing a
preliminary legend based on visual interpretations using a mirror stereoscope for air
photographs, followed by screen digitization. An automatic classification method was appliedto identify and delineate the different LULC units for the satellite image.
As the aerial photographs had been taken 32 years previously, the interpretation and
classification based on them could not be checked against ground truth. In contrast, the 2004
satellite image was taken during the research period and could be directly checked against
ground truth. To establish the classification in the latter case, six homogenous areas were
selected for each LULC unit as a testing site. Then the maximum likelihood classification
method was applied for identifying land use and land cover types for the study area as a whole.
The post-interpretation and classification phase involved preparation of LULC maps from both
the 1972 aerial photographs and the 2004 satellite image of the area, followed by detection and
recognition of their changes. Based on the first two, a third map was prepared showing LULC
transformations using the overlay function of ArcView Spatial Analyst software. Then, the
type, magnitude and trend of the LULC changes and their impact on the environment were
evaluated. The collected household socio-economic and demographic data were processed
using SPSS to generate descriptive statistics. The qualitative data obtained through group
discussions and interviews conducted with local authorities and experts in local agricultural
8 A member of the research team who surveyed the biodiversity status in the study area.
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offices, together with the descriptive statistics of the qualitative household data, were used to
identify the causes of LULC and to assess the impact of the changes on the livelihoods of the
rural population.
The 10 soil samples collected from different LULC types were analysed in the Holeta Soil
Laboratory (it is located in Oromia region, 45 km away from the capital Addis in the south).
The sample soils were first air dried, lightly ground and passed through a 2 mm sieve, and then
conventional analytical methods were used following procedures described by the Ministry of
Natural Resources Development and Environmental Protection (MoNRDEP 1990). Soil texture
was determined by the hydrometer method, total nitrogen determined by the Kjeldahl method,
and pH using a pH meter in a 1:1 soil to water ratio. The organic matter in the soil samples was
calculated first by determining the soils organic carbon content using the Walkley-Black
method, and then it converting to organic matter by multiplying by a factor of 1.724. Available
phosphorus (P) was identified using the Olsen and Bray II methods and potassium (K
+
) by theammonium acetate method. Then the laboratory test results were summarized using
percentages, one-way analysis of variance (ANOVA) and a least significant difference (LSD)
test, which in turn were used to characterize the soils of different LULCs, and thereby the
consequential effects of LULC changes on the soils were able to be reviewed.
LAND USE AND LAND COVER CHANGES IN THE UPPER DIJ O RIVER
CATCHMENT
Patterns of land use and land cover distribution: Six LULC types were identified in the
area: riverine trees, tree plantations, perennial cropland and settlement,9 shrub-grassland, land
used for growing annual crops, and bare land/open grassland. The description of each land use
and cover type is listed in Table 1.
9
Perennial croplands and settlements are treated as one category because perennial crops such as enset and chat weregrown in areas immediatelysurrounding peasant tukuls and it was not easy to distinguish the boundaries between them.
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Table 1: The LULC types identified in the Upper Dijo River catchment.
LULC Types Description
Riverine trees Trees grown along stream courses, including indigenous tree species
and exotic trees such as eucalyptus and juniperus trees.
Tree plantations Areas planted with exotic trees, mainly eucalyptus and juniperus
trees, and not found near river courses.Perennial crops and
settlements
Areas with ensetand chat treecrops, together with rural settlements(tukulsand avenues).
Shrub-grassland Areas with a cover of shrubs and short trees mixed with grasses.
Land for annual
crops
Areas used for growing annual crops such as wheat and barley.
Bare land/open
grassland
Areas with a cover of stunted and scant grass, and wastelands with
exposed rocks and badlands.
The proportion and distribution of LULC types by hectare and per cent, grouped by slope
class, is shown for 1972 and 2004 respectively in Tables 2 and 3 and Figs. 2a and 2b. In the
two periods considered, land used for growing annual crops was more important in the Upper
Dijo River catchment. It covered more than one-third (33.4%) of the total area in 1972,
followed by perennial crops and settlements (25.3%) and shrub-grassland (20.3%). Lands that
were under all types of trees, including riverine trees and exotic wood lots, together accounted
for 17% of the catchment area, while wastelands (i.e. areas with rock outcrops and badlands)
and areas with stunted and scant grass covered 4.1% of the basin area. In 1972 the riverine tree
cover was two times more than that of exotic tree plantations.
In 2004 the coverage of annual crops increased to 41% of the total area. Perennial crops and
settlements accounted for 24%, while waste lands and stunted and scant grass covered 18.4%.
The remaining area was occupied by riverine trees (1.8%), exotic tree plantations (7.3%) and
shrub and/or grassland (7.9%) (Fig. 2b).
The pattern and distribution of LULC types in different slope zones remained more or less similar
during the two periods. Approximately 80% of the LULC of the area occurred in an area where the
degree of slope was less than 15%; 15.3% of the total catchment area is located in a zone with a
slope of 1530%. Only 6% of all areas covered by different LULC types, particularly croplands
and shrub-grasslands, were located in zones with slopes exceeding 30%.
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Table 2: Distribution of the LULC of the Upper Dijo River catchment in 1972.
Land use and land cover types
Riverine tree Tree
plantations
Perennial crop
& settlements
Shrub-
grassland
Land for annua
crops
Bare land/open
grasslandTotal Area
Slope
class(ha) (%) (ha) (%) (ha) (%) (ha) (%) (ha) (%) (ha) (%) (ha) (%)
55 0.41.4
0.064.1
14.0
1.36.9
23.7
0.57.7
26.6
0.79.9
34.1
0.530.0
0.0
0.029.0 0.52
Total
623.6
11.2
100 319
5.7
100 1408.2
25.3
100 1129.
20.3
100 1858.7
33.4
100 230.8
4.1
100 5570.0 100* The upper figures refer to percentages calculated row-wise while the lower ones are computed column-wise.
Table 3: Distribution of the LULC of the Upper Dijo River catchment in 2004.
Land use and land cover types
Riverine trees Tree
plantation
Perennial
crops &
settlements
Shrub-
grassland
Land for
annual crops
& settlements
Bare
land/open
grassland
Total Area
Slope
class
(ha) (%) (ha) (%) (ha) (%) (ha) (%) (ha) (%) (ha) (%) (ha) (%)
550.6
2.2
0.62.8
9.6
0.79.4
32.5
0.70.5
1.6
0.110.3
35.6
0.55.4
18.5
0.5329.0 0.52
Total101.4
1.8
100407.2
7.3
1001334.4
24.0
100442.
7.9
1002258.9
40.6
1001025.6
18.4
1005570. 100
* The upper figures refer to percentages calculated row-wise while the lower ones are computed column-wise.
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PATTERN OF CHANGES IN LAND USE AND LAND COVER
Table 4 shows the pattern of changes in LULC between 1972 and 2004. Land used for growing
annual crops increased by 22% compared with the previous amount of cover and accounted for
8% of the total area. Bare land/open grassland and tree plantations showed similar patterns of
change, with increases of 345% and 28% respectively in the 30-year period. However, the
expansion of land/open grassland was approximately fivefold while that of tree plantations was
relatively less significant. In contrast, riverine tree cover showed a reverse trend, reducing by
84% during the same period of time. Shrub-grasslands showed a similar pattern of change and
decreased by 61% in this period. Lands used for perennial crops and settlements also showed a
decline, by approximately 5%, which may have been due to encroachment by annual crop
cultivation. In general, the pattern showed a tendency towards more land being brought under
annual crops, while at the same time tree plantations became more important at the expense of
shrub-grassland and riverine trees. In contrast, more and more land became degraded and was
abandoned.
Table 4: Pattern of LULC changes between 1972 and 2004 in the Upper Dijo River catchment.
Area (1972) Area (2004)Change between
1972 and 2004
Average rate of
changeLand use/cover
units (ha) % (ha) % (ha) (%) ha/yr (%)
Riverine trees 623.6 11.2 101.4 1.8 -522.2 -84 -16.3 -2.63
Tree plantations 319 5.2 407.2 7.3 +88.2 +27.7 +2.8 +0.87
Perennial crops
and settlements
1408.2 25.3 1334.4 24 -73.8 -5.24 -2.3 -0.16
Shrub-grassland 1129.7 20.3 442.5 7.9 -687.2 -60.8 -21.5 -1.9
Land for annual
crops1858.7 33.4 2258.9 40.6 +400.2 +21.5 +12.5 +0.67
Bare land/open
grassland230.8 4.1 1025.6 18.4 +795 +344.5 +24.8 +10.77
Total 5570.0 100 5570.0 100 ----- ----- ------ ------
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2a
2b
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Figure 2, a and b: Land use and land cover map of the Upper Dijo River catchment in 1972 and
2004.
Figure 3: Land use and land cover change map of the Upper Dijo River catchment between
1972 and 2004.
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Table 5: Matrix of land use and land cover change in the Upper Dijo River catchment.
Note: Figures in parentheses represent LULC that showed no change.
Table 5 and Fig. 3 show that only 7.5% of the area that was covered with riverine trees in 1972
remained the same in 2004. The remainder (92.5%) was cleared and had changed to other land
use/cover types by 2004: 10.5% to tree plantations, 22.7% to perennial crops and settlements,
11% to shrub-grassland, 29.2% to land used for growing annual crops, and 19% to bare
land/open grassland. In contrast, conversion of other land use/cover types to riverine treesamounted only 8.7% compared with 92.5% that was lost to other land use/cover types (Table
5). Further, only approximately 10% of the area that was covered with shrub-grassland in 1972
was still under the same cover in 2004. The rest (90%) was transformed to other LULC types
in 2004: 2.6% to riverine trees, 5% to tree plantations, 18% to perennial crops and settlements,
32% to land used for growing annual crops, and 31.8% to bare land/open grassland. The area
that was changed from other land use/cover types to shrub-grassland was small and accounted
for only 29% compared to the amount of shrub-grassland lost to other types (Table 5).
Land use and land cover units in 2004 (ha)
Riverine
trees
Tree
plantations
Perennial crops
& settlements
Shrub-
grassland
Land for
annual
crops
Bare
land/open
grassland
Total
area
Riverine trees 46.9 (7.5%) 65.6 141.9 69.0 181.8 118.4 623.6
Tree plantations 19.6 26.1 (8.1%) 59.3 43.7 96.8 73.6 319
Perennial crops &
settlements0.7 132.4 445.1 (31.6%) 98.4 579.5 152.2 1408.2
Shrub-grassland29.2 55.6 206.0
115.2
(10.2%)364.4 359.3 1129.7
Land for annual
crops1.0 119.3 465.1 88.0 968 (52%) 217.2 1858.7
Landuse/coverunits
1972
(ha)
Bare land/opengrassland
4.0 8.2 17.0 28.2 68.3 105 (45.5%) 230.8
Total area 101.4 407.2 1333.4 442.5 2258.9 1025.6 5570
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Of the total cultivated area and wastelands in 1972, 52% and 46% respectively remained
unchanged; 32%, 10% and 18% respectively of the original covers of perennial crops and
settlements, shrub-grassland and exotic tree plantations showed no change, while the
remaining largest portions of these LULCs were changed to other types of cover. Thus, it is
apparent that the three LULCs were most at risk of undergoing change.
Table 6: Distribution of changed and unchanged land use and land cover types by slope class in
the Upper Dijo River catchment area between 1972 and 2004.
Land use/cover types remained unchanged (ha)
Slope
class
Areas
changed
(ha)Riverine
trees
Tree
plantations
Perennial
crops &
settlement
Shrub-
grassland
Land for
annual
crops
Bare
land/open
grassland
Total
area
55 22.2 0.03 0.3 2.5 0.1 3.8 0.0 28.9
Total 3863.7 46.9 26.1 445.1 115.2 968.1 104.9 5570
Table 6 shows the pattern of changed and unchanged LULC types between 1972 and 2004 in
various slope zones, expressed in per cent. Approximately 3860 ha, accounting for 69% of the
total area of the catchment area, underwent change from one land use or land cover type to
another land use or land cover types, while the remaining 31% of the area remained under the
same use and cover type. Further, 94% of the changed land use and land cover types were
located on slopes of less than 30%.
With regard to agriculturally suitable terrain in terms of slope, i.e. areas in the 30% slope class
or less, 3100.3 ha (55.7%) were already under cultivation for annual crops in 1972 (Table 3)
and 3373.4 ha (64.3%) were under cultivation for perennial crops in 2004 (Table 4). This
Formatted: Left
Formatted: Centered
Formatted: Left
Formatted: Left
Formatted: Centered
Formatted: Left
Formatted: Left
Formatted: Centered
Formatted: Left
Formatted: Left
Formatted: Centered
Formatted: Left
Formatted: Left
Formatted: Centered
Formatted: Left
Formatted: Left
Formatted: Centered
Formatted: Left
Formatted: Left
Formatted: Centered
Formatted: Left
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implies that more areas with gentle slopes (
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Land tenure system: Before the 1975 land reform, land in Ethiopia was the property of a few
landlords. This was also the case in the Upper Dijo River catchment area. Of the sample
households, 65% were petty landowners (gebar) and 14% were tenants (chisegna). Both gebar
and chisegna did not own any land. After the 1975 land reform, local people who were petty
landowners and tenants were ensured of their right to use their landholdings.
Figure 4: Causes and consequences of land use and land cover changes and farmers
responses. (The green arrow indicates positive change however; the red arrow indicates negative
change).
The 1975 land reform, which resulted in the change in ownership of land by a few landlords to
ownership distributed among many peasants, has probably adversely influenced the pattern of
Populationpressure
Increase demand for:
Fuelwood
Food Othernecessities
Expansion ofcroplandstowards
forest, shruband marginal
lands
Destruction ofremnant forests
& shrubs
Land degradation: soilerosion, decline in soil fertilityand expansion of bare land
Destruction offorests;
Use of cropresidues &
animal dung forfuel wood
Destruction offorests
The 1975land reform
Landredistribution
Emergence of newhouseholds
Increase demandfor food, fuel wood
& shelter;Illegal landtransactions
Conversion offorest areas tocropland and
settlement areas
Farmingsystem
Traditionalfarm
implementsmaresha &kember
Cutting oftrees
Reduction incrop yields
Extensification orintensification of
cropland
Destructionof remnant
forests
Increase thevalue added
to land
Improve-ments in
soilmanage-ment
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land use and land cover changes in the area. The redistribution of landownership resulted in the
emergence of new households, which in turn led to increased demands for food and hence
cropland and other basic necessities. As a result, forest areas were converted to cropland and
areas for settlements (Fig. 4). Thus, the 1975 land reform resulted in problems of land
consolidation, expansion of cropland and the destruction of natural forests in the area. The
latter has resulted in increased amounts of bare land and changes in soil properties. Moreover,
the land tenure system which prevailed after the 1975 land reform gave peasants use rights
only. In response, the local people have engaged in illegal land transactions in the form of
weled aged (illegal way of transferring land to another person), which has resulted in the
reduction of landholding size and allows land to be used by rich peasants. This has aggravated
the level of poverty among the people.
Landholding size: Table 7 shows the average landholding size per household in the study
area. In 2004 the average landholding size in the study area was nearly 0.7 ha (2.8 timad) andthe holdings ranged from 0.13 ha to 2.5 ha. However, there were slight variations within the
sample transects. The average landholdings were 0.74 ha in Transect 1, 0.86 ha in Transect 2,
0.55 ha in Transect 3, and 0.63 ha in Transect 4. The average holding size was less than 1 ha.
Thus, the holding sizes were very small, which indicates high population pressure on existing
land resources.
Per capita landholdings in 2004 were 0.09 ha in Transect 1, 0.12 ha in Transect 2, 0.08 ha in
Transect 3, and 0.09 ha in Transect 4. The difference in per capita holdings between transects
was due to variations in population size and the total area of the transects.
Table 7: Distribution of households and landholding size in 2004.
Number of respondentsHousehold size
Tr. 1 Tr. 2 Tr. 3 Tr. 4 Total area
5 4 5 9 7 25
68 7 17 18 9 51
9 9 14 12 9 44
Total 20 36 39 25 120
Landholding (ha)
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0.5 10 13 25 13 62
0.51 8 15 10 11 43
>1 2 7 4 1 14
Total 20 36 39 25 120
A total 93% of respondents reported that their holdings had decreased over the previous threedecades, for several reasons: 48% of the respondents reported that the 1975 land reform and its
consequent land redistribution was one of the main factors, while 23% attributed the decrease
to soil erosion and gully expansion, and 17% to increased population pressure. A few
respondents (12%) claimed that part of their landholding had been snatched by Keble Peasant
Association leaders and transferred to others in the form of weled aged. In contrast, a few of
the respondents indicated that their holdings had increased during the previous three decades.
When asked where the extra land had come from, many of them replied that they had bought it
informally from other holders. According to a local official,10
this traditional way of
transferring land to another person has aggravated the level of poverty in the area. In addition,
it may further complicate the problems of implementing the new land certification process,
which has implemented by the countrys main regions started in 2003 modelled in an effort in
Tigray during the late 1990s.
Land fragmentation: Another problem related to the land tenure system was fragmentation of
land. In the study area the number of plots held by a person ranged from one to five plots, and
the average was two. However, there was no variation within transects. With regard to travel
time on foot, the average distance from any given homestead to all plots was approximately 13minutes. However, slight variations among transects were observed: travel time was 11.8
minutes in Transect 1, 13.89 minutes in Transect 2, 11.54 minutes in Transect 3, and 16.21
minutes in Transect 4.
Land fragmentation is a constraint to land management and the intensity of cultivation. This
was clearly observed in the study area, where peasants planted enset around their homesteads
and invested more in their enset fields compared to farm plots located further away. They
10 Ato Tale Geta, Team Leader, Silte Wereda Extension and Communication Office
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added manure and crop residues to enset fields and gave more attention and care. According to
the respondents, they did not add manure and crop residues to land used for growing annual
crops. Hence, soil fertility is expected to decrease more rapidly in such plots which are located
further away from homesteads.
FARMING SYSTEM
Crop production: A further influential factor that has led to the changes in the pattern of land
use and land cover is the traditional nature of the farming system in the area. The farming
system is a mixed type, where both crop farming and livestock production are carried out on a
subsistence basis. The subsistence nature of the farming system has contributed to the pattern
of land use and land cover change through the cutting of trees in order to prepare traditional
farm implements such as maresha (traditional ploughs), kember (a part oftraditional ploughs)
and hand hoes, and also the expansion of croplands towards forest areas and grazing lands to
increase yields to feed the growing population (Fig. 4). The expansion of croplands hasresulted in the destruction of natural forests. Similarly, the expansion of croplands into grazing
lands has led to a decline in livestock production. Today, most of the lands which are suitable
for crop production are already cultivated. Hence, the only option to increase crop production
is to use croplands more intensively. Due to shortage of land, peasants are compelled to shift
from extensification to intensification by increasing labour and other inputs. However,
peasants do not have access to fertilizers due to their prohibitively high prices. Moreover, they
use their available supplies of manure and crop residues on enset fields and as feed for
livestock rather than applying these to land used for growing annual crops. As a result, there is
no return of organic matter to restore the fertility of land used for growing annual crops. This
has resulted in declining soil fertility and a drop in agricultural productivity.
Livestock production: As in all other parts of the country, livestock are an integral part of the
cropping system in the study area. The total number of livestock of the sampled households
was 376, equivalent to three livestock per household. Cattle accounted for 78%, sheep and
goats for 11.4%, and horses, donkeys and mules for 10.6%. In terms of Tropical Livestock
Unit (TLU),11 the total number of livestock of the sampled households was 237. The average
11 TLU (Tropical Livestock Unit) is equivalent to 250 kg live animal weight.
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holdings of households were 2.15 TLU in Transect 1, 2.13 TLU in Transect 2, 1.74 TLU in
Transect 3, and 1.98 TLU in Transect 4.
Oxen are the major source of drought power in the study area. However, nearly 44% of the
households did not have any oxen and of those who did possess oxen, 51% had only one ox per
household and 5% had only two oxen per household. This has created serious problems for the
efficiency of farming activities in the area.
With regard to the trend in livestock numbers, as many as 82% of the respondents reported that
livestock numbers had decreased in the area, while 8.5% of the sample households reported an
increase in numbers; the remaining 9.5% reported that there had been no change in numbers of
livestock. Approximately half (52%) of respondents indicated that the main reason for the
decrease in the numbers of livestock per households had been shortage of animal feed, while
approximately 30% attributed the decrease to the death of livestock due to animal diseases,14% attributed it to the selling of cattle due to poverty, and the remaining 4% claimed it was
due to other problems such as seasonal shortages of labour.
According to 57% of the respondents the main factor behind the shortage of livestock feed was
the expansion of cropland (Plate 1), 22% claimed it was the expansion of gullies, while 21%
claimed that drought was the major cause.
Plate 1: Expansion of cropland towards grazing land.
Sources of energy: Fuel wood and cattle dung have been the most important energy sources
(biofuels) in rural Ethiopia in general and in the Upper Dijo River catchment in particular; 60%
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of the respondents confirmed that fuel wood was most important, while 35% confirmed that
cattle dug was most important. A few respondents (5%) told that they used crop residues as
energy sources. However, such usage was not found to be significant because peasant
households often use crop residues for animal feed rather than energy sources (Fig. 4).
IMPL ICATIONS OF LAND USE AND LAND COVER CHANGES
Land use and land cover changes degrade or enhance the lands capacity for sustained use and
regaining its natural cover. Specifically, changes in land use and land cover have a significant
influence on soil resources and biodiversity.
Implications for soil degradation: Table 8 shows that the sand fraction was higher in open
grassland and lower in cropland and degraded land in the study area. In contrast, the clay
fractions were found to be highest in degraded lands and croplands and lowest in open
grassland and soils from reference sites. Hence, the general trend in soil texture in conjunction
with the pattern of land use and land cover change is not in agreement with the findings of
Woldeamlak & Stroosnijder (2003) who reported low clay content in cultivated soils. This is
due to the fact that the soil samples taken from degraded and cultivated lands by Abyiot (2005)
were unfortunately all on vertisols, particularly on depositional sites, which are rich in clay
content. Further, the absence of natural forest cover in the area may have affected the results.
Table 8: Soil properties (030 cm) of four land use and land cover types.
Land use/cover types
Soil properties Cropland aOpen
grassland aDegraded
lands a
Reference
sites * Average
Clay 43.75 30.00 55.00 39.00 41.94
Silt 33.39 36.25 22.5 33.00 31.30
Sand 22.86 33.75 22.5 28.00 26.8
pH 1:1 H2O 5.52 6.37 6.075 6.15 6.03
Total N (%) 0.197 0.23 0.11 0.23 0.193
Available P (ppm) 7.1 4.5 4.2 6.37 5.54
Organic C (%) 3.228 3.275 1.365 3.689 2.889
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C/N ratio 17.27 14.32 12.085 15.83 14.88
SOM (%) 5.57 5.65 2.36 6.4 4.995
K+((c mol(+)/kg)) 1.322 1.359 1.226 3.107 1.754
Notes:
Cropland refers to annual crops,
* References are sites which include farm boundaries and holy sites which are believed to have not suffered fromland use or land cover change.aSoil sample results obtained by Abyiot Legesse (2005)
The total nitrogen (N) content of the soils showed differences among different land use and
land cover types. It was highest in control and open grassland soils (0.23%) and lowest in
degraded soils (0.1%) (Table 8). An LSD test revealed that degraded soils significantly
differed from all others in terms of total N, and in general degraded lands were found to have a
low total N. This may be due to soil erosion and leaching. The same result was obtained by
Wakene & Heluf (2004).
The soil organic matter (SOM) content was found to be highest in reference soils (Table 8).
When compared with soils from reference sites, the soils under crop, open grass and degraded
lands had average SOM contents of 87%, 88% and 37% of soils from the reference sites,
respectively. It seems that human influences have resulted in a drop in SOM content. This
finding is in line with those of Mulugeta (2004) and Woldeamlak & Stroosnijder (2003).
However, the ANOVA and LSD test did not show significant variation in SOM among
different land use and land cover types. This may be due to the absence of natural forests and
the subsequent widespread soil degradation due to erosion by runoff in the study area.
The available phosphorous (P) content ranged from 4.2 ppm in degraded land to 7.1 ppm in
cropland (Table 8). The highest concentration of available P was observed in croplands, which
could be due to the effect of application of chemical fertilizers, especially DAP (diammonium
phosphates)on croplands. This result is in line with the findings of Woldeamlak & Stroosnijder
(2003), but contradicts those of Wakene & Heluf (2004). However, the available P content of
the soils had statistically significant differences among the different land use and land cover
types.
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The potassium (K+) content of the soils varied among the different land use and land cover
types. It was highest in reference soils (3.11 (C mol (+)/kg)) and lowest in degraded soils (1.23
(C mol (+)/kg)) (Table 8). This result is similar to that of Wakene & Heluf (2004), who
reported a higher K+ content from virgin land than from cultivated and abandoned lands.
However, the ANOVA did not show a significant variation in K+ among the different land use
and land cover types. This is in agreement with the findings by Woldeamlak & Stroosnijder
(2003), who reported insignificant difference in K+ among different land uses.
The differences in the pH of soils under different land use and land cover types were small
(Table 8). Cropland soils were moderately acidic (pH = 5.52), while open grassland, degraded
and reference soils were slightly acidic (pH ranged from 6.08 to 6.37). However, the trend of
soil acidity for cultivated lands showed that intensive cultivation and continuous use of acid-
forming inorganic fertilizers had accentuated the level of soil acidity. Soil pH directly affects
plant growth through the effect of the hydrogen ions, and indirectly through the effects on
nutrient availability (Woldeamlak & Stroosnijder 2003).
Implications for biodiversity loss: The natural vegetation and tree species of the Upper Dijo
River catchment have been under threat. Focus group discussions confirmed that Kosso
(Hagenia abyssinica), Sobla, Kulkual (Euphorbia abyssinica), Wadesha, Korch (Erythrina
brucei), Gulo (Ricinus communis), and Mesena are some of the most severely threatened
species of trees, which are on the verge of extinction. Even Sembelet (Hyparrhenia) and
Sendedo(Pennisetum) are becoming severely threatened due to excessive and unwise use for
thatching as well as for manufacturing traditional artefacts. In addition, Sigeda(Oleaceae) and
Zigba (Podocarpus falcatus) trees are becoming extinct in the study area. Regarding food
crops, peas (Pisumsativum) and lentils (Lens culinaris) are avoided by peasants due to their
vulnerability to attacks by pests and monkeys.
Generally, land use and land cover change have resulted in soil degradation, the removal of
topsoil, leading to loss of soil fertility, and the depletion of biodiversity, which in turn leads to
irreversible deterioration of natural resources. These findings are in line with those of empirical
studies by Mulugeta (2004) and Woldeamlak & Stroosnijder (2003).
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FARMERS RESPONSES12
Response to the scarcity of fuel wood: The scarcity of wood for fuel and other uses has
forced people to plant eucalyptus trees. All of the sample households had planted eucalyptus
trees around their homesteads, along and inside gullies, and on degraded lands (Plate 2).
Further, the local official13 reported that 250 ha of land in Anshebeso and Arat Berkebeleshad
beenplanted with eucalyptus trees.
Eucalyptus trees have grown widely and have become the dominant tree type in the area. The
respondents in the focal group discussions indicated that the main reason for preferring
eucalyptus trees was their fast growth and tolerance of environmental stress. However, the
peasants suggested that the eucalyptus trees have adverse effects on the ecology, especially on
water resources by causing desiccation, and consequently the land may not be used
productively in other ways. For this reason the peasants in the study area do not expand their
croplands into the eucalyptus tree plantations, but keep reasonable distances in between.
Plate 2:Eucalyptus trees planted by farmers in badly degraded lands.
Despite their adverse impact, eucalyptus tree plantations have continued to expand rapidly. The
respondents associated this with the trees role in controlling the expansion of gullies. It was
reported that many people plant trees to stop the expansion of gullies into their cropland and
grazing areas and thereby they also met their household needs for fuel wood and other
12 The responses refer to the conservation measures taken by farmers to alleviate the adverse effects of land use
and land cover change on their livelihood and the environment.13 Ato Tale Geta, Team Leader, Selti Wereda Extension Communication Office.
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necessities. In response the question where do you plant trees? the farmers (household heads)
answered along and inside gullies.
Farmers participation in soil and water conservation: The respondents were aware of the
problems of soil erosion that existed in the area and tried to tackle these by applying some
conservation measures. Almost all (98%) of the respondents used soil and stone bunds while
only 2% used check dams to alleviate the problem of soil erosion in the area.
Soil fertility management systems: As a consequence of the study area being very densely
populated, access to new land has become very limited. Hence, there is growing pressure on
the limited resources. This has forced farmers to cultivate marginal lands, discontinue the
practice of fallowing, and stop the use of crop residues to maintain soil fertility. As a
consequence, land management is necessary to prolong cultivation periods and feed the
growing population. In this respect, the peasants in the study area have employed a variety ofmeasures, including improving the fertility status of the soils (95% of respondents) and
changing the land use type (5% of respondents).
Most of the respondents were engaged in improving soil fertility, using different methods to
maintain the fertility levels of the soils: 53% used artificial fertilizers, 37% used manure, and
10% used crop rotation and other methods such as fallowing. Most of the farmers mainly
applied manure to enset fields, while for cereal crops they used commercial fertilizers and
practised crop rotation. Hence, the decline in soil fertility is accelerated on plots that are
located further away from homesteads. This finding is in agreement with that of Tilhun et al.
(2001) who reported that homestead plots in the Gununo area in Southern Ethiopia are given
continuous applications of manure, compost, household waste, and ash.
CONCLUSIONS AND RECOMMENDATIONS
This study has revealed that the recent advancements in spatial technology, namely remote
sensing and GIS, could provide powerful tools for evaluating land use and land cover changes
at catchment levels. Heterogeneous data types, specifically aerial photography and satellite
images, provided valuable data for this study. Using these advanced technologies together with
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field-based detection, quantified changes in land use and land cover were calculated for the
study area in the Upper Dijo River catchment between 1972 and 2004. The general trend
observed was a decrease in shrub-grassland at a rate of 21.5 ha per year and a decrease in
riverine trees at a rate of 16.3 ha/yr. A corresponding increase was observed in bare land/open
grassland (24.8 ha/yr), cropland and settlement areas (12.5 ha/yr), and tree plantations (2.8
ha/yr). The decrease in riverine trees and shrub-grassland partly reflects the considerable
degradation of natural vegetation in the area.
The current ecological problems of the Upper Dijo River catchment and the associated land use
and land cover changes can be related partly to the livelihoods of the local population, i.e.
socio-economic conditions and access to agricultural, public and institutional services, and to a
certain extent the population growth. In the Upper Dijo River catchment, as in much of rural
Ethiopia elsewhere, the local people live in abject poverty. Further, the area is one of the most
densely populated areas of the country, with an average of 7.8 persons per household. Landand livestock form the basis of peoples livelihood. However, landholdings per household have
been declining and today the rate is 0.7 ha/household. This is due to the growing and unabated
population pressure. In addition, the productivity of land has declined over time. However,
neither Malthusian nor Boserupian assertions can completely account for the relationship
between the people and the environment in the study area. This is due to both land degradation,
mainly the expansion of bare land (in line with Malthusian perspectives), and environmental
recovery, which has resulted from household tree plantation activities (in support of Boseupian
perspectives).
The change in land tenure and growing fragmentation of land following the 1975 land reform
has accentuated the changes in the pattern of land use and land cover. In this respect, however,
it is not land redistribution, as in other parts of the country, but rather it is the illegal
transactions of land from person to person (weled aged) which has aggravated land
fragmentation and poverty levels in the area. Hence, demographic factors alone are not
responsible for environmental degradation. Non-demographic factors have strongly influenced
the dynamics of the environment in the area too.
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The land use and land cover change and associated problems observed in the area have
environmental implications at local, regional, national, and international levels because the
consequences of degradation have no boundaries. In this regard, soils in open grasslands
showed higher sand content, but lower available N, P, K+, and soil organic matter (SOM)
compared to soils in the reference sites. This is a major threat to the agricultural sector of the
study area. Moreover, the biodiversity of the area is highly threatened.
There is a trend towards more people, more trees in the study area, which is in line with the
reports made by Muluneh (2003; and unpublished data, 1994) and Woldeamlak (2002), but in
contrast to the findings of Kebrom & Hedlund (2000), Gete (1997) and Belay (2002). This
trend may be a result of the ongoing community afforestation programme and private
initiatives to check the expansion of gullies around croplands. The household level tree
planting practice is a praiseworthy initiative because it could have ecological advantages.
However, the increase in tree plantation coverage does not imply a favourable change towardssustainable land use and land cover because most of the newly planted areas are planted with
eucalyptus trees (to check the expansion of gullies) which are known to have numerous
negative ecological effects.
The following recommendations are made:
The people in the study area are confronted with problems of poverty and resource
degradation which require solutions which integrate development and conservation
measures. Hence, further development and environmental planning in the locality
should take into account the direction and magnitude of land use and land cover change
patterns. In addition, solutions to the problems of land use and land cover change
should include improving the productivity of the agricultural sector through technical
intervention, creating off-farm employment opportunities for the population, and
reducing human and livestock population pressure on the land. The local people must
be involved in all development activities and resource conservation in order to ensure
sustainability.
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Although the area of land under tree plantation has increased, the general trend in land
use and land cover change in the area has not benefited soil fertility. For this reason,
multipurpose agro-forestry should be introduced that can satisfy the need for wood,
livestock fodder, soil fertility improvement, and soil and water conservation.
As the study area is located in the Great Rift Valley system, where relatively recent
rock formations and major and minor faults are found, physical factors such as
physiographic location, age of rock formation and fault lines have influenced the area
along with the human factors. However, to date no study of the impact of these physical
factors on the local environment and the livelihoods of the people has been conducted.
This gap invites further investigations into the impact of physical factors on the patterns
of land use and land cover change and also the associated problems of the environment
and the livelihoods of the people in the study area.
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Addis Ababa University
Ethiopia
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Acta Geographica-Trondheim is the continuation o Papers from the Department
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