The invasion of Prosopis juliflora and Afar pastoral livelihoods in the Middle Awash area of Ethiopia
© Mehari. 2015
Received: 22 June 2015
Accepted: 28 September 2015
Published: 5 October 2015
An evergreen shrub, Prosopis juliflora is one of the most invasive species in arid and semi-arid areas. Since its introduction to the Middle Awash area of Ethiopia, it has invaded a huge acreage of grass- and rangelands which are life-supporting unit for Afar pastoralists.
Survey, using group discussion and questionnaire, was made to study the effect of P. juliflora invasion on Afar pastoral livelihoods. The obtained data were analyzed using Wilcoxon signed-rank test, chi-square analysis, and logistic regression.
According to the result, 84 % of the total surveyed households rated P. juliflora as undesirable species even though the bush was often used for fuelwood, fencing homesteads, and barn and house construction. Invasion of P. juliflora was also blamed to limit transhumance, occupying settlement areas and affecting multipurpose trees/bushes and grass availability. All these effects put pressure on the livestock assets causing about 80 % livestock loss, testing the pastoral livelihoods heavily. Each household, on average, lost 6.5 small stock and 7 cattle during the past 10 years due to health hazards caused by P. juliflora pod. Consequently, P. juliflora as a source of income was considered by a quarter of the surveyed pastoral households, with the age of a household head and change in livestock asset being influential variables in decision-making.
In sum, P. juliflora invasion has made livestock rearing extremely difficult which raised pastoralists’ ecological vulnerability in the fragile ecosystem they possess.
Prosopis juliflora (Swarz) DC, commonly known as mesquite, is an evergreen tree/bush native to the Caribbean, Central and northern South America (Pasiecznik 1999). P. juliflora has a very wide ecological adaptability which can grow on soils from sand dune to clay soil, and from saline to alkaline soil type, below 200 to above 1500 m above sea level, and with a mean annual rainfall ranging from 50 to 1500 mm (Pasiecznic et al. 2004; Zeila et al. 2004). Because of the wider ecological adaptability, P. juliflora had been extensively planted in the 1970s and 1980s in deforested and desertification prone areas for reclamation as well as a source of fuelwood and fodder for rural community (Pasiecznik et al. 2001, 2004). However, despite the anticipated benefits, in many cases, it has remained being a major irritant for local people by interfering with resource use systems. The species has occupied millions of hectares of land which were under different land use systems in Australia, coastal Asia, and Southern and Eastern Africa (Sudanupdate 1997; Pasiecznik 1999; Catterson 2003). According to a report by Invasive Species Specialist Group (ISSG), Prosopis spp. is one of the top 100 invasive plant species (Lowe et al. 2004).
Invasive plants like P. juliflora are also characterized by vigorous growth which helps them to outcompete indigenous plant species to cover huge areas of land in a relatively short period of time (Manchester and Bullock 2000; D’Antonio and Kark 2002). The invaded lands could be of different use systems, such as rangeland and riverbank, to interfere with rural livelihoods activities by impeding land use system and incurring extra costs to check the expansion (Shackleton et al. 2006). When P. juliflora appears on grazing lands, it reduces grass cover and thereby affects stocking density (Pasiecznik 1999), and in severe cases, it can form impermeable dense thickets.
In Ethiopia, documentation is lacking regarding when, from where, how, and by whom the alien invasive P. juliflora was first introduced, but speculation exists. The earliest time of notice is believed to be in the late 1970s in the eastern part of the country where India is a probable source (EARO and HADRA 2005). If the speculation holds, the seed sources of P. juliflora for India and sub-Saharan Africa were with inferior phenotype and a non-palatable type (Alban et al. 2002). According to Kassahun et al. (2005), P. juliflora found in Ethiopia are thorny and mostly characterized by bushy growth nature, confirming the inferior quality of the introduced germ plasm. In the Middle Awash area of Ethiopia, P. juliflora was introduced some three decades before (personal communication with elders at Worer, Afar region). By that time, pastoralists were told about the multipurpose uses of the plant such as pods as an additional feed for their livestock, trunks as a source of fuelwood, and the plant itself as reclaiming degraded and salt-affected lands. Anticipating the benefits, the local people were willing and thus P. juliflora was planted over large areas in the region by campaigns like Food for Work Program until 1988 (EARO and HADRA 2005).
The purposeful planting has given the plant an opportunity to base in the Middle Awash area. Besides its inherent robust growth, the viable P. juliflora seeds surviving in livestock and warthogs’ droppings serve as a vehicle for the plant to reach distant areas to have unchecked expansion throughout the region (Hailu et al. 2004). Currently, more than 30,000 ha of grasslands, rangelands, water points, and croplands are estimated to be occupied by P. juliflora in the Middle Awash area. The invasion is still continuing. These invaded resources are basically key resources for livestock rearing, which in turn are the main stay for Afar pastoralists in their fragile ecosystem. Therefore, the objective of this study was to assess the perception of Afar pastoralists of the Middle Awash area about P. juliflora invasion in the context of their livelihoods and also to investigate the effect of P. juliflora invasion on Afar pastorals’ vulnerability to recurrent moisture stress the area experiences.
Study area and sampling
Data collection and analysis
Group discussion with community elders (five elders from Sideha-Faghe, Halaideghe, and Worer and four elders from Gewane area) was carried out before the employment of survey. Group discussion was made in August 2007, and survey was conducted both in August 2007 and 2012. Structured interviews, open- and closed-ended questions, were used to collect data. Group discussion checklists and questionnaire for household survey are found in Additional file 1. Personal observations were also used to understand the situations during the survey. In this study, the household served as a unit of analysis. Because of cultural norm, it is the household head who is expected to speak on the household’s behalf. Most households were male headed, and even for the few widows, the matured son acted as head of the household. As a result, quite few respondents were females. However, housewives of most interviewed households were also involved in answering open-ended questions. During the survey, cards shaded with different colors in different proportions were used to ease answering questions having proportions as a response. Wilcoxon signed-rank test was done for matched-pair comparison between past and current individual household’s livestock assets and chi-square analysis to compare frequencies.
Logistic regression was also used to identify influential variables to use P. juliflora as a source of income and for diversification of livelihood strategies in a given household. In the logistic regression, logit model was estimated using maximum likelihood method for predefined explanatory variables. The livestock asset of each household in the regression model was measured by tropical livestock unit (TLU). TLU commonly takes 250 kg live weight as a standard of unit, and accordingly, the TLU conversion factor for camels, cattle, and small stocks is 1, 0.7, and 0.1, respectively (Jahnke 1982). Worer was used as a reference place as it is a source of P. juliflora for the rest of the locations in the study area.
Afar pastoralists’ perception about P. juliflora
The awareness of the pastoralists about the existence of P. juliflora in the Middle Awash area was assessed. Accordingly, about three fourths of the respondents knew the bush after 1985. With regard to its importance, 84 % of the surveyed pastoral households perceived P. juliflora as a harmful bush, whereas only 2 % of the households replied as beneficial, and the remaining 14 % of the households considered the bush as having both beneficial and harmful effects. The proportion of respondents who replied P. juliflora being both beneficial and harmful was higher for Worer, Amibara, and Sideha-Faghe than the rest of the villages. In these three villages, there was a trial campaign carried out for 2 years (2002–2004) to minimize the spread of the bush by utilization, where pastoralists were organized in groups to produce charcoal out of P. juliflora and also to use its pods for fodder after grinding. As a consequence, these villagers might have realized that some benefits can be obtained from P. juliflora.
Benefits of P. juliflora for Afar pastoralists
The benefits and effects of P. juliflora to pastoral households in the Middle Awash area of Ethiopia
Benefits of P. juliflora
Means of income
For barn construction
For house construction
For making traditional bed (Olo’ytaa)
Effects of P. juliflora
Wet- and dry-season grazing land invasion
Traditions and institutions
Competition for labor
Thorn punctures (both livestock and inhabitants)
Settlement areas invasion
Shelter to predators
Shelter to rustlers
Logit P. juliflora as a source of income model: maximum likelihood result (response variable, Y = 1 if a household uses P. juliflora as a source of income, Y = 0 otherwise)
Age of household head
Primary school dummy (1 = yes, 0 = no)
Polygamy status (1 = yes, 0 = no)
Change in livestock asset
Division in which household is located (reference is Worer)
Amibara (1 = yes, 0 = no)
Awash Arba (1 = yes, 0 = no)
Halaideghe (1 = yes, 0 = no)
Gewane (1 = yes, 0 = no)
Sideha-Faghe (1 = yes, 0 = no)
Number of observations
Effects of P. juliflora invasion on Afar pastoralists
We [Afar men] always hold machete to clear P. juliflora on our ways. These days, a herd which used to be cared by one is demanding more people for protecting cattle from entering into deep thicket on their way to grazing site. Once they get in to the deep thicket, it is very difficult to get them out. The other effect is, for example, there are cattle who know their home/place: even if you leave them on grazing field, they will come back to the village by their own before sunset. This is no longer happening after P. juliflora invasion. They cannot locate their home, everywhere is P. juliflora and cattle get ‘confused’ (Respondent number 55; 35 years old).
Along with the invasion, 71 % of the respondents said that predators are nearer to their village than before in the hideout created by P. juliflora. According to them, nocturnal predators like hyena eats trapped livestock even during the day.
P. juliflora invasion and forage/fodder availability
Perceived proportion of grazing lands invaded by P. juliflora on the six villages of the Middle Awash area
Less than half invaded
Half to two thirds invaded
Two thirds to three fourths invaded
Three fourths and above invaded
Plant species perceived to be threatened by P. juliflora invasion in the Middle Awash area
Frequency of respondent
Frequency of respondent
P. juliflora invasion and Afar traditions
A high proportion of the respondents felt that P. juliflora invasion has undermined some traditions and institutions of Afar pastoralists (Table 1). In Afar culture, there is a high degree of reciprocity—if a household loses its livestock asset due to rustling, epidemics, or other agents, the risk is divided among the whole clan; thereby, the household gets some stocks for rebuilding its stock asset. However, nowadays, the possibility for risk division is very rare as each household is under pressure of losing its livestock asset due to narrowed dry- and wet-season grazing lands caused by P. juliflora encroachment.
P. juliflora and Afar pastoral livelihoods
For Afar pastoralists, pasture and livestock are key components of their livelihoods. Livestock asset comparison was made between “before” and “after” P. juliflora invasion within a household (Fig. 4). The current livestock holding of individual household was about 20 % of what they had before P. juliflora invasion. The Wilcoxon signed-rank test (T +) showed that the reduction is highly significant for all livestock categories within a household. The main reasons given for the reduction in livestock assets were shortage of pasture due to P. juliflora invasion (48 %) followed by recurrent drought (40 %) and disease (10.6 %). Those who mentioned drought as a major factor also said that P. juliflora invasion aggravated the rain shortage problem. According to them, before P. juliflora invasion, they used to have enough dry pastures on the field even during drought season. Besides, a disease which is locally called Armeko, characterized by twisted neck and dental disfiguration, caused by eating P. juliflora pod was accused for fueling the problem. Each household, on average, lost about 6.5 sheep/goats and 7 cattle in the past 10 years due to a complexion caused by the pod. The continual reduction of livestock asset a household experienced made it very difficult to depend on sole pastoralism driving them to look for additional means of stay.
Logit diversification of livelihood strategies model: maximum likelihood result (response variable, Y = 1 pastoralism and/or others, Y = 0 pastoralism only)
Age of household head
Primary school dummy (1 = yes, 0 = no)
Polygamy status (1 = yes, 0 = no)
Change in livestock asset
Perceived size of grazing land invasion (1 = above 2/3 is invaded, 0 = 2/3 or less is invaded)
Division in which household is located (reference is Worer)
Number of observations
Majority of the pastoralists realized the presence of P. juliflora in the Middle Awash area about 30 years ago. In all the surveyed villages, pastoralists use P. juliflora as homestead hedge/fence and for fuelwood. However, most women complained about pricking by the thorn during fuelwood collection and also the deterring smoke P. juliflora wood has while using it for cooking, especially when the wood is wet. On top of these, according to the respondents, structures of fence, house, or barn made from P. juliflora (Fig. 2) collapse sooner than those made from indigenous sources like adengali (C. rotundifolia), e’ebto (A. tortilis), and kasalto (A. nilotica). The reason given was that wood from P. juliflora is very susceptible to wood-boring insects which makes structures made from it collapse sooner. Most of the uses of P. juliflora were abundant driven; otherwise, according to the respondents, they would prefer to use indigenous plants.
P. juliflora invasion has affected fodder/feed availability on grazing lands of the Middle Awash area. Studies showed that encroached grazing lands have low stocking capacity and reduced herbage yield (Mugasi et al. 2000; Moleele et al. 2002; Angassa 2005). In the case of P. juliflora, its effect on grazing lands can reach to an extent of turning pasture lands into totally unusable bush lands (Getachew 2002; Hailu et al. 2004). Apart from its effect on grazing lands, P. juliflora pod causes twisted neck and dental disfiguration (called Armeko) of cattle and goat/sheep resulting in livestock losses. Armeko, based on the respondents, is severe during drought season as the livestock heavily depend on P. juliflora pods for survival. Similar problem was also reported by Esther and Brent (2005). Tabosa et al. (2006) observed that prolonged consumption of P. juliflora pod affects cranial nerves, controlling neck muscle, of cattle. In spite of these effects, the pod is nutritionally rich (Benedito 1988; Pasiecznic et al. 2004; Esther and Brent 2005), and livestock can depend on it to survive drought season (Ellis and Swift 1998). Nevertheless, the experience of the Afar pastoralists is, unless the pod is mixed with other feeds, solely dependent on P. juliflora pod during drought can be lethal for livestock.
The other problem associated with P. juliflora invasion is its hindrance on transhumance, a seasonal migration for search of feed. However, transhumance is one of the risk management strategies used by pastoralists to maintain their livestock asset. Transhumance allows marked recovery of grazing lands due to de facto “protected” grazing and also enables optimum utility from the grazing lands (Western and Nightingale 2002). Following the introduction of P. juliflora to the Middle Awash area, grazing lands of different seasons have been invaded, limiting transhumance to a maximum. The limitation in transhumance has in turn resulted in overgrazing of remained pasture sources leaving pastoralists with low number of stocks. Similar problems were also reported in Kenya and India (Gavali et al. 2003; Esther and Brent 2005). As a result, the pastoralists’ resilience to environmental uncertainties is impaired by raising their ecological vulnerability (Swallow 1994; Mariara 2005).
The P. juliflora’s effect on the life-supporting unit of pastoralist, grazing land, has made sole dependency on pastoralism less likely. Measures, such as cultivation of land, share cropping, formal employment in mechanized farms and other organizations, and engaging in casual labor and small trade have been taken by Afar pastoralists to secure their livelihoods. Pastoralists use various adaptive risk management strategies to enhance their resilience and secure their livelihoods when sole dependency on livestock is in question (Swallow 1994; Little et al. 2001).
In conclusion, in the Middle Awash area, P. juliflora is a strong competitive bush with low beneficial traits for Afar pastoralists. The bush has reached a level to impair the pastoral livelihoods in different ways like (a) reducing pasture availability; (b) inhibiting mobility; (c) having poisonous thorn for both the people and their livestock; (d) having pods posing health hazard for livestock; and (e) threatening traditions and institutions. The effects mentioned are interlinked and interacting with one another to heavily test pastoral way of life in the Middle Awash area putting them extremely vulnerable to environmental uncertainties.
I wish to thank Professor Fred Håkon Johnsen of the Department of International Environmental Studies, Norwegian University of Life Sciences for his help in my inquiries. I wish to thank the Norwegian State Educational Loan Fund and Ethiopian Institute of Agricultural Research for providing the resources. I also wish to thank the managing editor and the anonymous reviewers for their constructive criticism.
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