4.1. Land Cover Changes between 1985 and 2011
The land cover changes between 1985 and 2011 were analyzed in the five study sites, namely Darito, Soda, Samaro, Haralo, and Did mega. The analyzed remotely sensed data detected considerable changes across the study areas. Specifically, grassland and bushland vegetation in the central and northeastern part of Darito had decreased, and this was connected with increases of cultivation as seen in the 2011 map. The central and eastern portions of the rangeland in Darito are the areas subjected to land conversion for cultivation because they are characterized by wet soils along the bottomlands where seasonal water-logging occurs (Figure 2
b, see also Figure 1
). The loss of woodland vegetation along the hill escarpments of Darito has also been attributed to the expansion of crop cultivation as revealed in the 2011 map. The present findings are supported by [32
] who found that the percentage of cultivated land increased in the Yabelo district of the Borana rangeland between 1960 and 2000 and caused a serious loss of natural vegetation in the rangeland. A similar loss of woodland vegetation in the Did mega site is also due to the expansion of cultivation activities (Table 3
). The implications of increasing cultivated areas in the rangeland are loss of grassland and bushland as detected in this study. This is a main concern regarding livestock and pasture because the bottomland grasslands are dry season grazing reserves and, therefore, converting them into croplands adversely affects critical grazing resources. The ecological implications of inappropriate farming techniques are the losses of vegetation biomass (grassland, bushland, and woodlands) and below ground carbon stocks, consequent, reduce the capacity of the rangeland ecosystems to store and to sequester carbon.
Apart from cultivation pressure, participants during group discussions explained that harvesting of bushes and wood trees for charcoal, fuel-wood, fencing, and construction purposes are other possible causes of vegetation fragmentation in the rangeland. The key informants such as the development agency officials in the Kebele clarified that expansion of cultivation and clearing of wood trees have led to increased loss of natural vegetation in the rangeland. The loss of vegetation such as bushes and wood trees will constrain the supply of fuelwood, fodder, non-timber forest product, and building materials available to the inhabitants. As it is, the proportion of woodland vegetation in the rangeland is very low. The loss of woodland vegetation in other African drylands is a common environmental problem, and it is mainly attributed to the expansion of cultivation [33
] and clearing of trees for charcoal and fuel-wood, in particular the northern rangelands of Ethiopia [34
]. Other changes are shown by the gains of woodland vegetation in the northwestern part of Soda, western Samaro and in Haralo (Figure 3
b), and such gains were possible in the mountainous escarpment because human interactions are limited. Specifically, within the Soda site, the areas that were dominated by bush vegetation in the 1985 map are now replaced by wood vegetation. This is a positive change for ecosystem integrity because woodland biomes have a high potential for above ground biomass storage hence carbon sequestration benefits. In the Haralo site woodland vegetation has increased to some extent and a wide proportion of the area is bare land.
The percentage of bare land increased significantly (Table 3
), and this is attributed to the expansion of cultivated areas and loss of vegetation cover. The increase in bare land is also linked to past land use and management practices related to grazing [15
]. A recent study showed that bare land areas extended adjacent to cultivated land (Figure 2
b and Figure 3
b), and the trend indicates that inappropriate farming techniques attribute to soil erosion and land degradation. During transect walks with farmers, some portions of the rangeland had already been degraded and a large gully erosion had advanced. The expansion of bare land exposes soil to erosion, leading to loss of nutrients and soil organic carbon [35
]. Consequently, the process alters soil carbon storage and sequestration benefits in the rangelands [37
]. The increase in bare land due to cultivation pressure in other rangelands of Africa have also been reported [38
] and the authors advocated that inappropriate land management poses a serious concern to ecosystem integrity and people’s livelihoods. Exceptional change occurred in the Soda site whereby the percentage of bare land decreased in the 2011 map, and such changes were attributed to the regeneration of grasslands and reduction in the area under cultivation.
Moreover, there is a significant increase in the proportion of grassland in Soda, Samaro, Haralo, and Did mega in the 2011 map (Table 3
). The recovery of grassland is attributed to the past interventions of the Southern Rangeland Development Unit (SORDU) project [15
]. The establishment of grassland enclosures and grazing cessation has contributed to the progressive recovering of grasslands. Extensive portions of the rangeland, which were dominated by bush vegetation in the 1985 map, have been colonized by grasslands in the 2011 map. Previous studies [16
] showed that bush encroachment had altered the availability of palatable grassland pasture and animal mobility. However, concurrent efforts made by the district government to clear bush trees have contributed to an increase of grasslands and a decrease in the proportion of bush vegetation. Current evidence suggests that the changes obtained in the grassland are associated with the implementation of the land rehabilitation program, in particular bush clearing, cessation of grazing, and creation of grassland enclosures. This is a successful story in the grasslands but diminishing bushland vegetation has negative effects such as risk of fire and loss of above ground vegetation biomass. The decrease of bushland put serious constraints on browser animals, such as goats, sheep, and other game animals, because they feed on bushes. Apart from the deterioration of fodder, loss of bushland vegetation limits access to fuel-wood, fencing and building materials, and inhibits harvesting of non-timber forest products, such as those with medicinal values. In terms of ecosystem services, a loss in bushland reduces the proportion of above ground vegetation biomass and carbon storage capacity. Other negative consequences could be soil erosion and possibly losses of soil organic carbon. Furthermore, a variable rainfall pattern is a major agro-climatic constraint that supports or limits cropping performance. Specifically, the inhabitants of the Soda site only practice pure pastoralists and crop cultivation to a limited extent. The comparison of the results of the change detection with the land ownership in the Soda site indicated that the site had the highest numbers of people without land from the 1960s to 1999, which differed from other Kebele (Table 6
, see also Figure 5
). Afterward, the number of agro-pastoralists started to increase from 2000 to 2012, and the change was attributed to the increase of socio-environmental constraints, in particular, aridity conditions of the area affected by topographical landscape. Nevertheless, the observed trend in the increase of the number of agro-pastoralists in the Soda site is not comparable to the land cover change. The analysis managed to capture observable land cover changes, but the numbers of agro-pastoralists sampled during the survey interviews were consisted of those farmers who started cultivation around the year 2000 and afterwards. Given the uncertainty of livestock production, diversification of livelihood with crop production in the study site is inevitable. In the Samaro site, the area is affected by the topography and it is characterized more by an arid climate than by precipitation. Such a climatic condition restricts cropping activities compared to other sites such as Haralo and Did mega, which are located on the lowland plain of Mega. A topographical difference, as clarified by [40
] is one of the key factors that influences the microclimate in Ethiopia. Other factors that might have contributed to the decrease in cultivated areas in Samaro could be soil characteristics, which differ across the four study sites. The comparison of the results of land cover change and cropping trends (Figure 5
) demonstrate a corresponding association whereby the number of agro-pastoralists started to decline from 2000 to 2012.
Built up areas also increased in Samaro Kebele (Table 3
), and this can be explained by the growth of Mega town due to the influx of immigration and natural increase. In the last category, the proportion of shrub/grassland vegetation decreased slightly, and those areas which were characterized by seasonal water-logging were subsequently colonized by grass, dwarf bushes or herbs. However, in some bottomlands of the Soda and Did mega sites, shrub/grassland vegetation increased. This is attributed to the accumulation of water-logging during rainy seasons. The intensity of water flowing to the bottomlands of Did mega is attributed to the spread of bare land and loss of vegetation cover. Inadequate construction of water breakers during rainy seasons has also contributed to increase of water-logging in the bottomlands.
The implications of cultivation in the rangeland were analyzed by evaluating the practices used by farmers to prepare and manage their land. Just like in many other African countries, slash and burn is a widely used practice for the preparation of fields in the study sites (Figure 8
). Continuous ploughing without fallow periods reduces the soil’s ability to produce humus and soil fertility. The consequences of this practice are loss of habitat and species, an increase in air pollution, and the release of carbon into the atmosphere [39
]. Soil erosion is one of the significant consequences of this practice in the study areas, and the intensity of erosions increased in the lowland areas. Figure 10
illustrates the effects of cultivation on the development of gully erosions in the Did mega site. This is attributed to inadequate adoption of recommended farming techniques such as construction of water breakers, terracing, and the planting of trees (Figure 9
). The results provide the insight that unsustainable farming practice is not a better way of using rangelands. It is, therefore, necessary to improve farming practices in order to minimize the loss of soil organic carbon and vegetation biomass.
From the above analysis, the changes (positive and negative) in land cover obtained here varied across the study locations. The greatest change is found as a large increase in the proportion of bare land in Haralo. The decrease in the proportion of bushland vegetation occurred in all five sites, and extensive increase in cultivated areas occurred in Darito to a greater proportion than in the rest of the sites. The results from this study establish a strong indication that increasing human pressure on land uses and the expansion of cultivation activities in the study sites have attributed to loss of vegetation biomass, soil erosion, and land degradation.
Development of gully erosions around cultivated land in the Did mega site (photo November 2012).
Development of gully erosions around cultivated land in the Did mega site (photo November 2012).
4.2. Drivers Contributing to the Expansion of Cultivation in the Rangeland
The analyses have shown that the expansion of cultivation in the studied sites is attributed to environmental constrains, socio-economic, and demographic factors. Demographic variables such as family size played a critical role in the study areas. The major role is the provision of a labor force for different livelihood activities both on and off farms. It appears that most families with more members in their households owned larger plots of land for cultivation. This is evidenced by the significant difference between family size and land size (Table 6
). According to [41
], the immediate factor influencing land use decisions at local level is the household. This appears to correlate with the situation in this study where the agro-pastoralists from the entire studied site are engaged in cultivation because they need to create additional income to support their families. The availability of a labor force in a household has also necessitated the expansion of cultivation in the studied sites. The association between the expansion of agricultural land in the semi-arid lands of Yatta sub-county and demographic variables such as population, has also been elaborated by [21
], and the authors found a significant association between the indices. Cultivation in the study sites is considered to be a major livelihood diversification option because incomes derived from selling grains help families to afford education costs of their children. In our results (Table 6
), most families with children in school depend more on crop production because it is a source of income. The experience across the study locations shows that it is rare to find families with school-going children that are do not participate in cultivation activities. The situation has led to an increase in the demand of land for cultivation across the study locations.
The agro-pastoralists interviewed specified that food insecurity was another factor contributing to the expansion of cultivation. Most agro-pastoralists in the study locations have been in an extremely vulnerable state of food shortage due to recurrent drought. As explained by the participants during group discussions, cultivation in the study locations began as far back as the 1960s, but few people were engaged. It was intensified by the worst drought incidents in 1984, 1985, 1992, and 2000 that caused severe livestock mortality and decline in household herds. According to [42
], the occurrence of drought leads the pastoral communities to be faced with food insecurity due to livestock mortality. Recurrent drought episodes are increasingly worsening livestock production; the majority of the pastoralists are embracing crop production in order to cushion themselves against food shocks. The pastoralists, therefore, have increasingly engaged in crop cultivation in the relatively wet sections of the rangelands (lowland plain areas) and in the sub-humid areas. Recurrent drought as a reason behind the expansion of cultivation across the study sites is similar to [24
] who reports other incidences of droughts in 1991 and 1992 and by [43
] who describes other drought incidences in the 1970s. According to the authors, variable rainfall and deterioration of livestock production have caused food shortages in the Borana rangeland, and thus in order to secure food grains, pastoralists have started crop production in the good years with rainfall. The authors noted a decline in the percentage of pure pastoralists from 15%, to 8%. Such a decline is also consistent with [19
] who found that 92% of the inhabitants of five peasant associations in the Borana rangeland were agro-pastoralists who relied on both livestock and crop production. The increase in agro-pastoralists in the present study is also explained by a progressive increase in households practicing cultivation from 1960 to 2012 in the Darito, Soda, and Did mega sites except for a slight decline that was obtained in the Samaro site from 2000 to 2012 (Figure 5
). The proportion of agro-pastoralists is evident with the increase in the number of households engaged in crop cultivation from 35% reported by [15
] to 87% reported by [43
]. The 92% figure obtained in the present study is also consistent with the figures obtained by [19
] in their studies.
The need to diversify income at household level is another factor that contributed to the expansion of cultivation in the study sites. The mean household income obtained in this study varied across the study sites (Table 4
), nevertheless, reported amounts were insufficient to support households’ basic needs. According to the agro-pastoralists, they claimed that their incomes had been declining due to unreliable livestock production. Although the initial income before the occurrence of droughts was not captured in this study, the mean incomes revealed across the study sites provide significant insight into the economic situation of the agro-pastoralists and its implications on the expansion of cultivation activities. Experiences from other pastoral areas of eastern African rangelands show that diversification of income through crop production is the key livelihood option [44
]. Income generated from crop production helps the pastoralists to buy food, support their families, and reconstruct their economies. Specifically, the money generated from selling food grains is used to pay school fees, pay for health services, begin petty business, and purchase livestock for post-drought recovery. A similar situation is reported by [19
., that the Borana agro-pastoralists are increasingly engaging in crop cultivation to rebuild their wealth. The majority of the pastoral households in the study sites are increasingly embracing crop production in response to the past devastating droughts that affected their livestock.
Another underlying driver behind the expansion of cultivation as mentioned by the key informants and also during group discussions is the increase of local and cross-border immigration that has led to the development of towns like Mega and Yabelo. The growth of towns has contributed to population growth and hence has led to a higher demand of land for cultivation. However, due to inadequate census data of population trends across the studied sites, it was not possible to cross-reference this assertion. Further investigation into this is recommended. Further evidence of population growth and land conversion in Eastern Africa rangelands have been described by [45
] for the case of Kajiado rangeland of Kenya and by [20
] for the Maasai pastoral areas. According to the authors, the Maasai pastoralists from Tanzania have embraced crop cultivation to complement livestock production, which seems to be deteriorating over time.
Moreover, verification of the impacts of recurrent drought and the expansion of cultivation activities were analyzed by testing the correlation between rainfall and the number of famers who started cultivation. Although the rainfall pattern in the study areas fluctuates greatly, there is no clear statistical mark to validate the influence of rainfall trend on dictating the farmers’ engagement in cultivation activities. The deviation in the rainfall and the fluctuation in the number of farmers are not statistically significantly correlated. The results are supported by [46
] who found that the rainfall trend in Southern Ethiopia did not show a significant decline but that the area was characterized by long-term fluctuations. It should be noted that the rainfall pattern of the study sites fluctuates below and above the average in some years. It is, therefore, possible that such fluctuation trends and recurrent droughts, as mentioned by the farmers and demonstrated in Figure 7
(a and b), could be the underlying basis for justifying the expansion of cultivation in wet areas of the rangeland and, on the other hand, it contributes to the decline in cultivation activities in other sites. According to [15
], 12% of the wet areas of the Borana rangelands can support rain-fed crop production (teff, sorghum, barley, and haricot beans); this makes the expansion of cultivation across the study sites possible.
Furthermore, according to the Ethiopian government land policy, land resource is communal, and it is the property of the federal government. When the key informants were asked about the land tenure system in Ethiopia, they pointed out that access to land could only be acquired through leasing, and this is regulated by the Ethiopian government. According to the federal government of Ethiopia, it issues ‘‘use rights’’ to the farmers to own land for the purpose of farming and prohibits them from selling land [47
]. Despite the existing regal procedures, informally, another possibility used by the agro-pastoralists in the study sites to acquire land is to purchase a plot of land from relatives. Nevertheless the survey could not explicitly explore to what extent such a system has attributed to land cover changes across the Kebele, but it is among the reasons mentioned during interviews. Moreover, the results further revealed that policy transformation in the 1970s and the intervention of development projects, in particular water projects, were additional factors leading to land use changes. Policy transformations such as privatization of the communal rangelands into private enclosures affected land use and traditional rangeland management and hence expansion of cultivation and the land cover changes [43
]. Despite the fact that cultivation is growing in the study locations, there are differences across the sites (Figure 5
), and the differences are attributed to the heterogeneous nature of the sites, socio-environmental conditions, availability of draught power (mainly oxen), and variable rainfall. With regard to crops grown in the studied sites, rainfall and soil are the major agro-climatic factors influencing crop performance. Specifically, rain-fed crops such as maize, haricot beans, teff, wheat, barley, and sorghum are preferred because of the suitability of the soil and the climate of the area. Apart from being sources of food, they are marketable and, therefore, a reliable source of income for households, and they are also an important source of animal fodder, especially during the dry season.