land-use and land-cover change and its environmental implications in a tropical highland watershed,...
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This article was downloaded by: [Queensland University of Technology]On: 21 November 2014, At: 09:05Publisher: RoutledgeInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
International Journal of EnvironmentalStudiesPublication details, including instructions for authors andsubscription information:http://www.tandfonline.com/loi/genv20
Land-use and land-cover change andits environmental implications in atropical highland watershed, EthiopiaWoldeamlak Bewket a & Solomon Abebe ba Addis Ababa University, Department of Geography &Environmental Studies , P.O. Box 150372, Addis Ababa , Ethiopiab Jigjiga University, Department of Geography , P.O. Box 27,Jigjiga , EthiopiaPublished online: 04 Jan 2013.
To cite this article: Woldeamlak Bewket & Solomon Abebe (2013) Land-use and land-cover changeand its environmental implications in a tropical highland watershed, Ethiopia, International Journalof Environmental Studies, 70:1, 126-139, DOI: 10.1080/00207233.2012.755765
To link to this article: http://dx.doi.org/10.1080/00207233.2012.755765
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Land-use and land-cover change and itsenvironmental implications in a tropical highland
watershed, Ethiopia
WOLDEAMLAK BEWKET*† AND SOLOMON ABEBE‡
†Addis Ababa University, Department of Geography & Environmental Studies, P.O. Box 150372,Addis Ababa, Ethiopia; ‡Jigjiga University, Department of Geography, P.O. Box 27, Jigjiga, Ethiopia
This study analysed long-term land-use and land-cover change (LUCC) in a highland watershedcovering an area of about 154 km2 in the Blue Nile basin of Ethiopia. Two sets of panchromaticaerial photographs (1957 and 1982) and a Landsat TM image (2001) were the main input datafrom which three land-use and land-cover maps were produced by employing geographical infor-mation systems/remote sensing techniques. These data were complemented by some socio-eco-nomic data that were generated by using household survey, key-informant interview and groupdiscussion methods. The results show that in regard to land-use and land-cover, the major changehas been the reduction of areas under natural vegetation cover and expansion of open grassland,cultivated areas and settlements. Over the four and a half decades considered, areas of forest anddense tree cover and shrub grassland decreased by 64 and 6%, respectively. Forest and dense treecover experienced the greatest change; from accounting for �9% of the total area of the watershedin 1957 to only �3% in 2001. In general, much of the de-vegetation occurred between 1982 and2001. Cropland and rural settlement showed a small but consistent increase between 1957 and2001. Riparian vegetation decreased during the first period, but increased almost to the same levelduring the second period by gaining land from the other land-use and land-cover types. Theobserved LUCCs were driven by a combination of proximate and underlying causes. These includeincreasing demographic pressure and associated demands on environmental resources, widespreadrural poverty and inadequate management of common property resources owing to poorly definedownership arrangements. There is a need for short-term and long-term strategies to ensure sustain-able land management and agricultural development in the watershed.
Keywords: Land-use change; Population; Poverty; Watershed
1. Introduction
Changes in land-use and land-cover have important environmental consequences at local,regional and global scales. At the regional and global scales, these changes have profoundimplications for global radiation and energy balances, alterations in biogeochemical cycles,perturbations in hydrological cycles and loss of biodiversity at genetic and species levels[1–3]. At the local scale, changes in the use of land and its cover affect watershed runoff,micro-climatic resources, groundwater tables, processes of land degradation and landscape-level biodiversity. All these have direct impacts on livelihoods of local communities. Thesemultifaceted environmental impacts can affect, immensely, food security and sustainabledevelopment [1–3].
*Corresponding author. Email: [email protected]
International Journal of Environmental Studies, 2013Vol. 70, No. 1, 126–139, http://dx.doi.org/10.1080/00207233.2012.755765
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Accordingly, land-use and land-cover change (LUCC) have been researched over the pasttwo to three decades [1,3,4], notably under the auspices of the LUCC project of the Interna-tional Geosphere–Biosphere Programme (IGBP) and the International Human DimensionsProgramme on Global Environmental Change (IHDP) [1,4–6]. A significant volume ofliterature has been produced, ranging from quantifying extent and rate of LUCC throughidentification of proximate and underlying causes of the change to development of predic-tive models. The focus of much of the research work has been on tropical deforestation,which is known to be ‘one of the primary causes of global environmental change’ [1,5,7].
Whereas the extent, rate, causes and consequences of tropical forest loss, as a globalenvironmental problem, have been well documented [5,7,8–11], much remains to be estab-lished at the local scale about the complex relationships between environmental, economic,social and institutional factors that induce changes in land-use and land-cover [1,12,13].Investigation of LUCCs at a local scale is important to understand drivers of the changeand the positive or negative impacts likely at the local scale. According to Lambin et al.[1], studies at local scale of LUCC can also help to reveal general principles to provide anexplanation and prediction of new LUCCs at larger spatial scales.
In Ethiopia, only a few studies are available on LUCC at the local level [14–23]. Thesestudies report different types and rates of LUCCs in different parts of the country over thedifferent time periods they considered. Land use change in Ethiopia has a general theme:conversion of natural vegetation to use for agriculture and livestock. In most cases, thereare reports that subsistence crop production has expanded into ecologically marginal areas.For instance, Tegene [17] reported a significant increase in cultivated land and decrease innatural vegetation cover between 1957 and 1986 in a micro-catchment (Derekollicatchment) in South Wello, North-central Ethiopia. According to Tekle and Hedlund [15],shrubland and grazing land replaced a large area of forests in Kalu district, South Welloover the period 1958–1986. Bewket reported that cultivated land expanded at the expenseof riverine vegetation cover [18] for Chemoga watershed in north-western highlands ofEthiopia over the period 1957–1998.
Zeleke and Hurni [16] documented expansion of cultivated land at the expense offorestland between 1957 and 1982 in Dembecha area, north-western Ethiopia. Increase incropland area at the expense of grazing land and forest was also observed in Fincha’awatershed, western Ethiopia [22]. In a study that covered a time span of a century, Dessieand Chirstiansson [24] found forest cover reduced from accounting for 40% at the turn ofthe nineteenth century to accounting for less than 3% in 2000 of the total area studied inthe south-central rift valley region of Ethiopia. In another study covering the same area,Dessie and Kleman [21] noted that forest cover was still covering 16% in 1972. In south-central Ethiopia (Guragheland), both forest cover and cultivated land expanded at theexpense of grazing land during 1957–1999 [19]. Amsalu et al. [20] found a significantdecrease in natural vegetation cover, but increase in plantations between 1957 and 2000 inBeressa watershed, in the central highlands of the country. Similarly, Alemayehu et al.[23] reported an increase in plantation forest cover between 1965 and 2005 in their studyof a semi-arid watershed in Tigray, northern Ethiopia, as a result of a watershedmanagement intervention.
These research works also showed that expansion of cultivated lands at the expense ofnatural vegetation covers has intensified the problem of land degradation, specificallythrough soil erosion by water. Land degradation through soil erosion by water is the mostthreatening environmental problem in Ethiopia. As estimated by Hurni [25], Ethiopia losesabout 1.5 millionmg of soils per annum. Of this, nearly half is estimated to come from
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cultivated fields, which make up only about 13% of the country’s total area. The estimatedrate of soil loss in the cultivated fields is 42mg ha–1 per year, or 4mm of soil depth perannum, which by all measures exceeds the rate of soil formation. With this rate of loss,many of the slopes of the highlands, where there is only a thin soil layer, will be totallystripped of the soil mantle in less than two centuries. On the other hand, more than 83%of Ethiopians derive their livelihood directly from the land resource; and this population isgrowing at the rate of �2.7% per annum, requiring food production increases of at leastthe same rate. Because this land degradation threatens rural livelihoods, there is a need toundertake further research on local-level LUCCs in the Ethiopian highlands. Such workcan help in designing local-specific and targeted interventions for land resourcesmanagement and rural development.
The general objective of this study was to evaluate LUCC and describe its environmen-tal implications in a typical highland watershed in the Blue Nile river basin of Ethiopia.The specific objectives were to (i) quantify and map LUCCs between 1957 and 2001; (ii)identify driving forces for LUCCs and (iii) describe environmental and socio-economicimplications of observed changes in land-use and land-cover. The spatial framework forthe study is a small watershed, which is considered by some researchers as the appropriatenatural spatial unit for integrated management of land and water resources [26,27].
2. The study site: the Gish Abay watershed
The Gish Abay watershed is located between 37°05′ E to 37°15′ E and 10°55′ N to 11°05′N, and has a total area of �153.5 km2 (figure 1). It is in Sekella woreda (district) of theWest Gojjam Zone in the Amhara National Regional State (ANRS). It is part of the north-western highlands of Ethiopia and is characterized by a mountainous and rugged terrainwith steep slopes. Altitude varies between 2000 and 3100m and slopes range from nearlyflat (< 2%) to extremely steep (> 60%). Nitisols and leptosols are the predominant soiltypes. As measured at the nearest meteorological station, Dangla (�30 km west of thewatershed), average annual rainfall is 1557mm, more than three-quarters of which occurs
Amhara Region
400 0 400 800 Kilometers
N
Gish Abay watershed in Sekela woreda
Figure 1. Relative location of the Gish Abay watershed in Sekela woreda, Amhara Region.
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only during the four months of June to September. We expect micro-climate within thewatershed to vary with altitude and topography, but measured data were not available. Themajor indigenous natural vegetation types include Juniperus procera, Arundinaria alpina,Ricinus communis, Morus alba, Olea europea subsp. cuspidata, Hagenia abyssinica,Dombeya torrida, Euphorbia abyssinica, Embelia schimperi, Erythrina abyssinica,Combretum molle and Ensete ventricosum. An introduced vegetation type that is widelyplanted by farmers is Eucalyptus globulus.
The Gish Abay watershed is, at the time of this study, inhabited by a total populationof �30,606 [28], a population density of �199 persons/km2. This is considerablyhigher than the average for the ANRS (111 persons/km2; [29]). The traditional mixedcrop–livestock agriculture is the single most important economic activity. The major typesof crops produced are barley, wheat, tef, potato, maize and millet [28]. Cattle, sheep, goats,horses and donkeys are the animals reared in the area. Crop production is mostly rainfed;only about 72 ha of land is under traditional irrigated agriculture.
3. Materials and methods
The materials used for this research were two sets of panchromatic aerial photographs anda satellite image (Landsat TM) for the years 1957, 1982 and 2001, respectively, andsocio-economic data generated through various methods of social research. The aerialphotographs were obtained from the Ethiopian Mapping Authority and the satellite imagewas obtained from the Institute of Geography of the University of Berne, Switzerland. Thedevelopment of the spatial database from the remotely sensed images included thefollowing procedures: (i) digitizing the study area in ArcView 3.2, (ii) scanning the aerialphotographs with a 600-dots-per-inch scanner, (iii) geo-referencing the photo mosaicsaccording to the Universal Transverse Mercator system by using topographic sheets of thearea, (iv) geo-referencing the Landsat TM image according to the same projection andusing the same topographic sheets and (v) delimiting and cutting out the study watershedfrom the database of the remotely sensed images (photo mosaics and Landsat TM image)by using the watershed boundary (superimposing) delineated from the topographic sheets.
The identification and classification of land-use and land-cover types from the aerialphotographs was undertaken visually based on tone, texture and pattern of features, withon-screen digitizing in ArcView 3.2. It also required intensive use of mirror stereoscopesfor verification from hard copies of the photos. As the two sets of aerial photographs weretaken more than 47 and 12 years ago, field verification was not possible. For the classifica-tion of the Landsat TM image, we used the supervised maximum likelihood classificationmethod in ERDAS Imagine 8.6. The maximum likelihood classifier assigns a pixel to aparticular class based upon the covariance information [30]. According to Richards [30], aconsiderably superior performance is expected from this method compared to otherapproaches to digital image classification. Training areas corresponding to each land-useand land-cover category were identified from fieldwork. For instance, churchyard forestswere used as training sites for identification of forest cover. The classification scheme waskept simple so as to minimize errors that can occur as details increase. Thus, only sevenbroad land-use and land-cover types were identified: forest and dense tree cover, riparianvegetation, shrub grassland, open grassland, cropland, homesteads and town. Table 1 givesa brief description of these land-use and land-cover types. For the purpose of comparison,many land-use and land-cover types produced from the multi-spectral Landsat TM image
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were synchronized to fit into the seven classes defined from the black-and-white aerialphotographs. In so reducing the number of classes, proper care was taken to minimizeerrors due to generalization. Finally, three land-use and land-cover maps were producedcorresponding to the three reference years, and temporal changes in land-use andland-cover were determined.
Methods used to examine socio-economic and institutional issues included (as well asremote sensing data) household survey and key informant interviews. For the householdsurvey, three villages were selected one each from upstream (> 2500m), midstream(2300–2500m) and downstream (< 2300m) parts of the watershed. We determined samplesizes from each village based on the proportion of surface area of each part out of the totalstudy area. Accordingly, 30, 29 and 24 households were randomly selected from an exist-ing register of households from upstream, midstream and downstream parts, respectively,making the total sample size 83. The key informant interviews were held with local elders,village (kebele) administrators and extension workers.
4. Results and discussion
4.1. Land-use and land-cover changes
Figures 2a, 2b and 2c shows the land-use and land-cover maps of the Gish Abaywatershed for the years 1957, 1982 and 2001. Tables 2 and 3, respectively, show areasunder the seven land-use and land-cover types during the three reference periods and thepatterns of land-cover dynamics. Descriptions of the changes in land-use and land-coverover the period under study now follow.
4.1.1. Forest and dense trees
The area in this category declined over the period under study; it accounted for about 9, 7and 3% of the total area of the watershed in 1957, 1982 and 2001, respectively. Of thetotal area under forest and dense trees in 1957, over 20% was cleared over the 25 yearsuntil 1982, and about 33% was converted to cropland and rural settlement. Between 1957and 2001, the area under forest and dense trees declined by �64%, which is a rate ofdeforestation and de-vegetation of �19 ha per annum. The rate of deforestation and
Table 1. Description of land-use and land-cover types identified in the Gish Abay watershed.
Land-use andland-cover type Description
Forest and dense trees Densely growing trees with undergrowth forming closed canopies and densely growingtrees without undergrowth. The dominant species are Arundinaria alpina and Ricinuscommunis.
Riparian vegetation Area covered by natural vegetation and planted trees along streams in the watershed.The dominant species in this category are Arundinaria alpina, Morus alba andEucalyptus globulus.
Shrub grassland Area covered with a mixture of short shrubs mainly Combretum molle and grasses.Open grassland Area dominantly covered by grasses with only a few widely scattered shrubs and trees.Cropland and rural
settlementArea used for annual crops, both rainfed and irrigated, and dispersed rural settlements.The separation of dispersed settlements from the surrounding farm plots from theremotely sensed images was very difficult; hence, lumped together.
Town Area occupied by a small town.
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Figure 2a. Land-use and land-cover map of the Gish Abay watershed, Ethiopia, in 1957.
Figure 2b. Land-use and land-cover map of the Gish Abay watershed, Ethiopia, in 1982.
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de-vegetation has been �11 ha and �31 ha per year during the first (1957–1982) andsecond periods (1982–2001), respectively. Only about 3% of the total forest and dense treecover in 1957 remained unchanged in 2001, whereas 43% was converted to cropland andrural settlement and 21% to open grassland. These patterns of change reveal that thedestruction of vegetation resources was caused by an increased demand for cultivable andgrazing lands. On the other hand, there has been little net gain from the other land covertypes changing into the forest and dense trees category (table 3).
According to local elders, the remaining little vegetation cover could be preservedbecause of protection by local community (traditional) leaders during more than fourdecades. According to Sekella Woreda Agriculture and Rural Development Office(SWARDO) [28], much of the study area is planned to be used for forestry development
Figure 2c. Land-use and land-cover map of the Gish Abay watershed, Ethiopia, in 2001.
Table 2. LUCCs in the Gish Abay watershed between 1957 and 2001.
Land-use andland-cover type
Area in1957 (ha)
Area in1982 (ha)
Area in2001 (ha)
% change1957 to 1982
% change1982 to 2001
% change1957 to 2001
Forest and dense trees 1342 1068 486 �20 �54 �64Riparian vegetation 2732 2539 2693 �7 6 �1Shrub grassland 2256 2167 2125 �4 �2 �6Open grassland 2544 2961 3074 16 4 21Cropland and rural
settlement6472 6593 6948 2 5 7
Town 6 24 26 300 8 333
Total 15,352 15,352 15,352 – – –
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in the area-specialization program of the ANRS. The local elders also stated that farmerswere being advised to have their own forests through a reforestation program to be orga-nized by the woreda agricultural and rural development office.
4.1.2. Riparian vegetation
The riparian vegetation, which includes natural vegetation and planted trees along streams,covered 18, 16 and 17% of the study area in 1957, 1982 and 2001, respectively (table 2).About 22% of this category remained unchanged during the first period, whereas theremaining amount was lost to other land-use and land-cover types, largely to croplands andrural settlement (34%). A major reason for the loss of riparian vegetation was expansion ofnewly established villages (both dispersed rural settlements and nucleated town-like settle-ments) around irrigated lands that are situated along the streams. Key informants said thatmany farmers had recently shifted their homesteads from hilltops and ridges to low-lyingareas where irrigable lands are situated, against the risk of wild animals and theft. On the
Table 3. Patterns of land cover dynamics in the Gish Abay watershed between 1957 and 2001.
Changed from Changed to
Percent change
1957–1982 1982–2001 1957–2001
Forest and dense trees Shrub grassland 14.5 15.4 14.4Riparian vegetation 21.2 18.9 18.4Open grassland 17.1 20.6 20.7Cropland and rural settlement 32.50.0 39.7 43.3Town 0.0 0.0 0.1
Shrub grassland Forest and dense trees 7.4 3.2 3.2Riparian vegetation 19.6 18.5 17.8Open grassland 19.2 20.1 19.7Cropland and rural settlement 38.6 44.1 44.9Town 0.0 0.2 0.2
Riparian vegetation Forest and dense trees 11.5 3.8 3.7Shrub grassland 14.8 14.4 14.1Open grassland 17.9 20.3 20.2Cropland and rural settlement 34.2 42.2 43.7Town 0.0 0.3 0.2
Open grassland Forest and dense trees 5.3 2.9 3.0Shrub grassland 14.7 13.6 13.7Riparian vegetation 16.5 17.7 17.2Cropland and rural settlement 43.2 45.8 46.1Town 0.1 0.2 0.3
Cropland and rural settlement. Forest and dense trees 3.9 2.6 3.0Shrub grassland 13.2 13.5 13.6Riparian vegetation 12.4 16.3 17.1Open grassland 20.0 20.0 20.1Town 0.2 0.1 0.1
Town Forest and dense trees 16.7 32.0 28.6Shrub grassland 0.0 12.0 14.3Riparian vegetation 16.7 28.0 28.6Open grassland 0.0 12.0 14.3Cropland and rural settlement 0.0 16.0 14.3
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other hand, the riparian vegetation category made some gains from the other land-use andland-cover types (table 3), as a result of which the total area in this cover category hasremained more or less constant over the period under consideration.
4.1.3. Shrub grassland
Of the total area of the Gish Abay watershed, shrub grassland covered about 15% in 1957.This remained more or less unchanged in 1982, but showed a slight decline in 2001 (table2). During the period 1957–2001, 45% of the shrub grassland was converted into croplandand rural settlement (table 3). But the gains in this category from the other land-use andland-cover types were considerable; hence, the total area under shrub grassland showedlittle change over the four and a half decades considered. The increased demand forcroplands, overgrazing and removal of shrubs for fuel wood, which can be expected fromthe increased human and livestock populations, were apparently the causes for changes inthe area coverage of shrub grassland.
4.1.4. Open grassland
This land cover type accounted for about 17% of the total area of the watershed in 1957.In 1982 and 2001, the open grassland accounted for about 19% and 20%, respectively, ofthe total area of the watershed. That is, the open grassland showed a slight increase duringthe entire period. The net gain was obtained from all of the other land-use and land-covertypes including croplands (table 3). According to key informants, the conversion ofcroplands to open grassland was a result of decline in land productivity and subsequentabandonment of cultivated fields. The decline in land productivity is attributable toaccelerated soil erosion and soil mining caused by over-cultivation and absence of appro-priate soil conservation measures. Part of the abandoned cropland will be converted backto cropland when soil productivity is regained, however.
4.1.5. Cropland and rural settlement
The largest proportion of the total area of the Gish Abay watershed has been covered bycropland and rural settlement throughout the study period. Cropland and rural settlementconstituted 42, 43 and 45% of the total area of the watershed in 1957, 1982 and 2001,respectively – a small but consistent increase. The expansion of this land-use type has lar-gely been a result of the conversion of open grassland, shrub grassland, riparian vegetationand forest and dense trees. The gain from a town settlement to the cropland and ruralsettlement category was a result of change in settlement patterns and the shift in position ofthe town, which have happened over the period studied. Expansion of the cropland at theexpense of natural vegetation covers was caused, according to key informants, by scarcity ofagricultural land through increasing population pressure. The average landholding of thesurveyed households was 1.2 ha, which is similar to the regional and national averages. But,about 75% of the surveyed households (n = 83) possessed6 1.1 ha. The declining productiv-ity of cultivated land, which was mentioned by the majority of the surveyed households, hascontributed to expansion of cropland area in an effort to compensate for lost yields.
4.1.6. Town
The small town of Gish Abay is situated within the study watershed. The size and positionof this town has significantly changed over the period studied. In 1957, the town was very
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small and located on a hilltop, where there are more rural homesteads at present. In 1982,the size of the town increased manifold and its position was shifted downstream. Duringthe second period, there was some increase in the area of the town; both apparentlythrough natural population increase and in-migration.
4.2. Drivers of LUCCs in the Gish Abay watershed
The drivers of changes in land-use and land-cover are often classified into proximateand underlying causes [6]. The proximate causes are the immediate actions of localpeople such as expansion of cropped areas, wood extraction, infrastructure expansionand others that change the physical state of land cover [5,31]. The underlying factorspush the proximate causes into immediate effect [5]. The underlying factors includechanges in demographic pressure, economic condition and technological and institutionalfactors [31].
4.2.1. Proximate causes
In the study area, both proximate and underlying driving forces caused the observedchanges in land cover. At the proximate level, expansion of cropland at the expense ofnatural vegetative covers such as forests and shrub grassland has been observed. Thisconversion was obviously driven by the need of the local people to produce food crops.Similarly, expansion of homesteads and the town, which replaced natural vegetative covers,was caused by the local people’s needs to meet their requirements for a living from use ofthe land. Deforestation and devegetation for the purpose of obtaining wood for domesticfuel, house construction and farm implements has evidently been a major immediate causeof destruction of natural vegetation cover, and it can be inferred from the increase inpopulation size. The average fuel wood use among the surveyed households was 1370 kgper annum. In addition to this, households use 960 kg of cattle dung and 580 kg of cropresidues per year, on average. Nearly 25% of the sample households reported that they sellfuel wood and/ or charcoal to generate cash income, which contributes to deforestation.
Asked to mention reasons for deforestation in their communities, half of the respondentscited increasing demand for cropland to be the major cause. Other reasons includeddemand for fuel wood and charcoal (41% of respondents) and demand for wood for houseconstruction, fencing and farm implements (8% of respondents). More than 90% ofrespondents admitted that they at times cut trees for the purpose of getting additionalcropland and/or wood for fuel and charcoal. The respondents also noted that forests andwoody vegetation used to be more abundant in the past. At present, the local administra-tion (the kebele administration) prohibits local people from cutting trees for fuel wood andcharcoal production, but key informants stated that the prohibition is ineffective and manyhouseholds still cut trees.
4.2.2. Underlying causes
Demographic pressure: In the developing countries, there is a significant statistical correla-tion between population growth and land-cover conversion, specifically deforestation[31,32]. Studies conducted in different parts of Ethiopia have also attributed LUCCsmainly to population growth [15,16,18,33]. In the study watershed, the total populationhad increased by 30% between 1984 and 1994; i.e. from 7535 to 9796. It then increased
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by 20% between 1994 and 2004, from 9796 to 12,539. With the increase in the humanpopulation, livestock population is highly likely to have increased as well. Over 75% ofthe surveyed households also asserted that livestock population had increased over timeand overgrazing of limited grazing areas was a major problem in their communities.Hence, population growth is undoubtedly a major factor in changes of land-use andland-cover in the watershed.
Poverty: People in the study watershed are engaged in subsistence mixed farming, withfew if any external inputs; it is thus of low productivity. The average landholding size ofthe sample households was 1.2 ha, with only 12% of them possessingP 1.5 ha. About92% of the sample households also stated that cultivable land was getting scarcer in theircommunities because of population pressure. As key informants noted, land was muchscarcer in the upstream part of the watershed because of the rugged terrain than in themidstream and downstream parts. On the other hand, average yield of cereals was onlyabout 600 kg per ha. The overwhelming majority of the people live in extreme poverty.Thus, dependence on land for livelihood, absence of alternative sources of employment,low productivity of cultivated land and the associated poverty have driven LUCCs in thestudy area. Indeed, the widespread poverty itself is partly attributable to overpopulationand the poor management of local environmental resources.
The land-tenure system: Land-tenure policies at the macro-level and existence andeffectiveness of local institutions for management of communal resources can contribute toLUCCs. According to Ostrom [34], absence of effective institutions and managementsystems is often the main cause for degradation of common pool resources elsewhere inthe developing countries. In Ethiopia, land is state-owned and farmers only possess rightsof usufruct; and there are no land-use and forest policies. According to Bekele [35], lackof appropriate land-use and forest policies and corresponding laws has significantly con-tributed to deforestation in the country. Abate [14] argues that the influence of land-tenureinsecurity on LUCCs was greater in south-western Ethiopia than that of population growth.This study did not attempt to gauge the role of the land-tenure system in the observedLUCCs. Yet, the secondary sources cited above [14,35] suggest that it might havecontributed to the LUCCs in the watershed studied, since the forests and shrublands arepoorly managed common property resources, with ill-defined ownership arrangements andwithout institutionalized systems of resource governance.
4.3. Environmental implications of the observed LUCCs
The changes in land-use and land-cover have multiple and profound environmentalimplications, such as loss of biodiversity and complexity, soil erosion, alterations in sur-face runoff, lowering of groundwater tables and disturbance in local climatic conditions.These can affect significantly food security and rural livelihood systems in the watershed.The major potential environmental consequences of the observed LUCCs in the Gish Abaywatershed now follow.
4.3.1. Implications for biodiversity loss
The study has shown that the area under natural vegetation in general and forests inparticular has declined over the past four and a half decades. This has implications for theloss of biodiversity in both flora and fauna, but we were unable to assess the exactmagnitude of the losses. According to Nyssen et al. [36], LUCC has historically contributed
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to loss of plant biodiversity in Ethiopia. The loss of plant biodiversity leads to a decline inecosystem integrity and loss of plant genetic resources. This, in turn, implies loss ofagricultural and pharmaceutical benefits.
4.3.2. Implications for soil erosion
Land-use and land-cover influences both the erosivity of the eroding agents and theerodibility of the eroding subject [37]. Experimental evidence has shown that land-use andland-cover are the most important determinants of soil erosion rates in the Ethiopian high-lands [33]. Soil erosion accelerates with removal of vegetation cover, and on eroded soils,vegetation growth is poor, which aggravates the problem of soil erosion. In the studywatershed, there has been extensive clearance of natural vegetation cover and replacementby settlements, open grassland and cropland areas. Thus, land area that is more vulnerableto soil erosion has increased over time, but it was not quantified by this study.
4.3.3. Implications for disturbance of local climatic conditions and hydrological regimes
LUCC influences local climatic conditions and the hydrological regime of watersheds. Forinstance, it can lead to altered radiation fluxes and energy budgets, wind speed, diurnaltemperature extremes, relative humidity content, rainfall partitioning process and surfacerunoff generation and annual stream flow patterns. Changes in land-use and land-coveralso contribute to the problem of global warming as the carbon locked up in biomass willbe released into the atmosphere, particularly when aggregated over a large spatial scale.Although this study did not include empirical data analyses, the observed LUCCs in theGish Abay watershed presumably had brought about such environmental consequences.
5. Conclusions
A quantitative evaluation and understanding of LUCC has practical significance for landresource management, as it has multiple environmental implications ranging from local toglobal scales. The aim of this study was to appraise LUCC in the Gish Abay watershed, akey headstream of the Blue Nile river, during the second half of the twentieth century(1957�2001). It is clear that there have been substantial changes in land-use and land-cover;the major change being reduction in areas under natural vegetation cover and expansion ofopen grassland, cropland and rural settlements and a town settlement. Forest and dense treescover was the most affected land-cover type, with nearly two-thirds of its area converted toother land-use and land-cover types between 1957 and 2001. Open grassland gained fromthe cropland and rural settlement. This is attributable to abandonment of some croplandarea as it became too degraded and unproductive to cultivate, largely because there was alack of proper soil conservation and soil fertility management. These findings corroborateresults of some earlier studies [15,16,18,20,21,24,33] that the general trend of land-use andland-cover dynamics in many parts of the Ethiopian highlands is to the destruction of naturalvegetation cover and expansion of cultivated and settled areas. The changes have importantenvironmental implications such as loss of biodiversity and complexity, alterations in surfacerunoff dynamics and lowering of groundwater tables, soil erosion and disturbance in localclimatic conditions. These have the potential to affect significantly local food security andrural livelihood systems, and also have impacts that transcend the boundary of the watershedsuch as sedimentation in Lake Tana, the source of the Blue Nile.
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The LUCCs were driven by a combination of proximate and underlying causes. Theproximate causes included increased demand to expand cropped areas, increased demandfor wood for domestic energy production and other uses, and expansion of settlements.The underlying causes, that push the proximate causes into immediate effect, wereincreased population pressure, poverty and the land-tenure system which leaves commonpool resources such as forests, shrublands, and riparian vegetation with ill-definedownership arrangements and without institutionalized systems of resource governance.
These two groups of factors ought to be confronted to bring about sustainable landmanagement and agricultural development in the watershed. As for the proximate causes,there is a need for short-term measures such as controlling expansion of croplands byincreasing productivity of existing cultivated fields through soil conservation and soilfertility management, encouraging private woodlot development around homesteads and,or introduction of community forestry programs and forestation of hillsides and degradedlands, planning and regulating expansion of settlements and pursuing a participatorymanagement approach for common property resources such as forests and grazing areas.The underlying causes call for long-term solutions. These include promoting developmentof the non-agricultural sectors of the national economy and easing population pressure onland, provision of modern sources of energy such as rural electrification and securing landand tree tenure to the land users. There is also a need to examine and quantify actualecological and livelihood impacts of the LUCCs in the watershed.
Acknowledgements
The paper has substantially benefited from the comments of the two anonymous reviewers.
References
[1] Lambin, E.F., Geist, H.J. and Lepers, E., 2003, Dynamics of land-use and land-cover change in tropicalregions. Annual Review of Environment and Resources, 28, 205–241.
[2] Steffen, W., Sanderson, A., Jäger, J., Tyson, P.D., Moore, B. III, Matson, P.A., Richardson, K., Oldfield, F.,Schellnhuber, H., Turner, B.L. II and Wasson, R.J., 2004, Global change and the earth system: a planetunder pressure (Heidelberg: Springer Verlag).
[3] Lambin, E.F. and Geist, H.J. (Eds), 2006, Land-use and land-cover change: local processes and globalimpacts (Heidelberg: Springer Verlag).
[4] Turner, B.L. II, Skole, D., Sanderson, S., Fischer, G., Fresco, L. and Leemans, R., 1995, Land-use and land-cover change (LUCC): science/research plan. HDP Report No. 7 (Stockholm: IGBP Secretariat).
[5] Geist, H.J. and Lambin, E.F., 2002, Proximate causes and underlying driving forces of tropical deforestation.BioScience, 52, 143–150.
[6] Lambin, E.F. and Geist, H.J., 2003, Global land-use and land-cover change: what have we learned so far?Global Change News Letter, 46, 27–30.
[7] Hartemink, A.E., Veldkamp, T. and Bai, Z., 2008, Land cover change and soil fertility decline in tropicalregions. Turkish Journal of Agriculture and Forestry, 32, 195–213.
[8] Brown, K. and Pearce, D.W. (Eds), 1994, The causes of tropical deforestation: the economic and statisticalanalysis of factors giving rise to the loss of the tropical forests (London: University College London Press).
[9] Houghton, R.A., 1994, The worldwide extent of land-use change. BioScience, 44, 305–313.[10] Bawa, K.S. and Dayanandan, S., 1997, Socioeconomic factors and tropical deforestation. Nature, 386,
562–563.[11] Murali, K.S. and Hedge, R., 1997, Patterns of tropical deforestation. Journal of Tropical Forest Science, 9,
465–476.[12] Kammerbauer, J. and Ardon, C., 1999, Land use dynamics and landscape change pattern in a typical
watershed in the hillside region of central Honduras. Agriculture, Ecosystems and Environment, 75, 93–100.[13] Semwal, R.L., Nautiyal, S., Sen, K.K., Ranaa, U., Maikhuri, R.K., Rao, K.S. and Saxen, K.G., 2004,
Patterns and ecological implications of agricultural land-use changes: a case study from central Himalaya,India. Agriculture, Ecosystems and Environment, 102, 81–92.
138 W. Bewket and S. Abebe
Dow
nloa
ded
by [
Que
ensl
and
Uni
vers
ity o
f T
echn
olog
y] a
t 09:
05 2
1 N
ovem
ber
2014
[14] Abate, S., 1994, Land use dynamics, soil conservation and potential for use in Metu area, Illubabor region,Ethiopia. Africa Studies series A13 Geographical Bernensisa (Berne: Berne University).
[15] Tekle, K. and Hedlund, L., 2000, Land cover changes between 1958 and 1986 in Kalu district, SouthernWello, Ethiopia. Mountain Research and Development, 20, 42–51.
[16] Zeleke, G. and Hurni, H., 2001, Implications and land use land cover dynamics for mountain resourcedegradation in the northwestern Ethiopian highlands. Mountain Research and Development, 21, 184–191.
[17] Tegene, B., 2002, Land-cover/land-use changes in the Derekolli catchment of the South Welo zone ofAmhara region, Ethiopia. Eastern African Social Science Research Review, 18, 1–20.
[18] Bewket, W., 2002, Land cover dynamics since the 1950s in Chemoga watershed, Blue Nile basin, Ethiopia.Mountain Research and Development, 22, 263–269.
[19] Woldetsadik, M., 2003, Population growth and environmental recovery: more people, more trees, lessonslearned from west Gurageland. Ethiopian Journal of the Social Sciences and Humanities, 1, 1–35.
[20] Amsalu, A., Stroosnijder, L. and de Graaf, J., 2007, Long-term dynamics in land resource use and thedriving forces in the Beressa watershed, highlands of Ethiopia. Journal of Environmental Management, 83,448–459.
[21] Dessie, G. and Kleman, J., 2007, Pattern and magnitude of deforestation in the south central rift valleyregion of Ethiopia. Mountain Research and Development, 27, 162–168.
[22] Tefera, B. and Sterk, G., 2008, Hydropower-induced land use change in Fincha’a watershed, westernEthiopia: analysis and impacts. Mountain Research and Development, 28, 72–80.
[23] Alemayehu, F., Taha, N., Nyssen, J., Girma, A., Zenebe, A., Behailu, M., Deckers, S. and Poesen, J., 2009,The impacts of watershed management on land use and land cover dynamics in Eastern Tigray (Ethiopia).Resources, Conservation and Recycling, 53, 192–198.
[24] Dessie, G. and Christiansson, C., 2008, Forest decline and its causes in the south central rift valley ofEthiopia: human impact over a one hundred year perspective. AMBIO: A Journal of the HumanEnvironment, 37, 263–271.
[25] Hurni, H., 1993, Land degradation, famines and resource scenarios in Ethiopia. In: D. Pimentel (Ed.) Worldsoil erosion and conservation (Cambridge: Cambridge Univ. Press), pp. 27–62.
[26] Bhatta, B.R., Chalise, S.R., Myint, A.K. and Sharma, P.N. (Eds), 1999, Recent concepts, knowledge,practices and new skills in participatory integrated watershed management: trainers resource book (Nepal:ICIMOD, PWMTA-FAO, and Department of Soil Conservation and Watershed Management).
[27] Bewket, W., 2003, Towards integrated watershed management in highland Ethiopia: the Chemogawatershed case study. Tropical Resource Management Papers 44. (Wageningen: Wageningen University).
[28] Sekella Woreda Agriculture and Rural Development Office (SWARDO), 2004, Annual Report for the Year2003/2004. Unpublished Report (in Amahric) (Sekella: Sekella Wereda Agriculture and Rural DevelopmentOffice).
[29] Central Statistical Authority (CSA), 2003, Statistical report on farm management practices, livestock andimplements. Part II. Agricultural Sample Enumeration, 2001/02 (Addis Ababa: Central Statistical Authority).
[30] Richards, J.A., 1994, Remote sensing digital image analysis: an introduction, 2nd ed. (Berlin: Springer-Verlag).[31] Meyer, W.B. and Turner, B.L. II (Eds), 1994, Changes in land use and land cover: a global perspective
(Cambridge: Cambridge Univ Press).[32] Bremner, J., López-Carr, D., Suter, L. and Davis, J., 2010, Population, poverty, environment, and climate
dynamics in the developing world. Interdisciplinary Environmental Review, 11, 112–126.[33] Hurni, H., Tato, K. and Zeleke, G., 2005, The implications of changes in population, land use and land man-
agement for surface runoff in the upper Nile basin area of Ethiopia. Mountain Research and Development,25, 147–154.
[34] Ostrom, E., 1990, Governing the commons: the evolution of institutions for collective action (Cambridge:Cambridge University Press).
[35] Bekele, A., 2001, Status and dynamics of natural resources in Ethiopia. In: Taye Asefa (Ed.) Food securitythrough sustainable land use: population, environment and rural development issues for sustainablelivelihoods in Ethiopia (Addis Ababa: NOVIB Partners Forum on Sustainable Land Use), pp. 133–164.
[36] Nyssen, J., Poesen, J., Moeyersons, J., Deckers, J., Haile, M. and Lang, A., 2004, Human impact on theenvironment on the Ethiopian and Eritrean highlands – a state of the art. Earth Science Reviews, 64,273–320.
[37] Morgan, R.P.C., 1995, Soil erosion and conservation, 2nd ed. (Harlow: Longman).
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