Prosopis
Prosopis is a genus belonging to the botanical family of Fabaceae, capable to bind atmospheric nitrogen and hence to contribute to soil fertility improvement. The genus comprises 44 species “of which 40 are native to the Americas”[1]. In Africa there are only two native Prosopis species: P. africana and P. farcta.[1]. Most of Prosopis species, particularly P. juliflora and P. pallida (which are of concern in this regard) are fast-growing, very drought resistant and can stand saline soils easily. Due to their high coppicing ability they out-compete native species. Furthermore, they are equipped with several physical and chemical defence mechanisms (thorns, venom etc.) which make them very difficult to manage and unpalatable for animals. They are deep-rooting up to about 20 m and thus can reach water table [1]. Some Prosopis species are often mentioned as the strongest invaders: “[…] in particular P. juliflora, P.glandulosa,P. pallida,P. chilensis, P. flexuosa andP. ruscifolia invade valuable farm- and rangeland and sometimes grow into impenetrable thickets, causing enormous ecological and economic damage as a result of competition with the native vegetation and with agricultural crops.” [1] It is also assumed that similar species, in particular P. juliflora and P. pallida, form hybrids which make the identification even more difficult.
Encroachment of Invasive Alien Species (IAS) is a globally common phenomenon and often has detrimental effects on rural households in developing countries. Ethiopia in particular is affected by invasion of several species of Prosopis spp.– predominantly P. juliflora – that have been growing out of control for already more than a decade [2]. The ecological consequences of this woody species encroachment have been devastating since rangeland areas are degraded and forage grass productivity has declined drastically as a result [3]. Besides impacts on the social fabric and rural livelihood systems, consequences also entail land degradation, which strongly influences the regional and national economic performance. So far, the economics of land degradation have mainly focused on general aspects such as soil erosion, salinisation or land use changes[4].
Prosopis in Ethiopia
The spatial extension of Prosopis in Ethiopia is difficult to assess since it is expanding rapidly, up to 18% per year[5]. According to estimates of Ryan (2011), one million hectares (ha) are already covered by Prosopis in Ethiopia[6], of which about 700,000 ha are located in the Afar Region. Prosopis rapidly spreads across both pastoral and agricultural lands leading to severe losses in ecological functions and, thus, to degradation. Other countries[7] such as South Africa, Niger, Yemen, Namibia and India are also threatened by environmental degradation through Prosopis as are surrounding areas in Eritrea, Somalia and Kenya.
The Afar Region in Ethiopia
The Afar Region, along the Awash River in north-eastern Ethiopia covers an area of 108,860 km², hosting a population of approximately 1.4 million people with around 87% living in rural areas, mostly depending on livestock production for multiple purposes such as food consumption, income-generation, transport and asset reserves[9].
The region is featured by extensive areas of bush lands and grassland used as pasture by local pastoral transhumant groups. However, almost 50% of the area is covered by sand and rocks while only 7% is estimated to be cultivable. Of utmost importance for the local pastoral population is the Awash River, which traverses large parts of the region and serves as a vital key resource. The areas where Prosopis has spread most rapidly are the seasonally inundated floodplains along the Awash River, in which rich pastures had previously offered key grazing resources during dry seasons and drought. Almost 90% of the Afar population are pastoralists or agro-pastoralists and their livelihood mainly depends on livestock production using rangeland[10].The Awash River also offers irrigation potential for agriculture. An increasing number of pastoralists have started practicing small-scale farming along the Awash River to diversify their livelihood systems, alongside a growing number of large-scale farms cultivating cotton and sugarcane. Both farm types are also negatively affected by the invasion of Prosopis.
Furthermore, Afar Region encompasses biodiversity hotspots[11] and several endemic species[12] and exhibits a complex diversity of ethnic groups, each having their own peculiar societal features. Large areas of Afar Region have already been invaded (Fig.2) over the past twenty years and a further spread must be expected.
Prosopis was introduced in the Afar Region in the early 1980s by the Ministry of Agriculture[14]. Its original purpose was to combat desertification around the large state-owned irrigated farms along the Awash River.[15] It began to spread invasively during the 1990s. A consecutive land use and land cover mapping based on digital satellite image classification gives reason to assume that the spreading of Prosopis coincides with the collapse of water control and irrigation systems after the overthrow of the socialist Derg regime.[16] Water, and especially the availability of subsurface ground water, is obviously one of the drivers of the invasion of Prosopis.
Environmental, social and economic impacts of Prosopis and control and management approaches
Several actions and approaches for integrated management of Prosopis and various control methods were tested and implemented in Afar Region over the last years by public institutions as well as NGOs and donor organisations, with generally poor results. So far, comprehensive knowledge on and awareness of the diverse impacts Prosopis has on land degradation, losses in ecosystem services as well as a comprehensive policy framework and policy action are missing in Afar Region. The problem has not been addressed appropriately yet, even though today Prosopis invasion seriously challenges pastoralists, agro-pastoralists and irrigated agriculture implying social, economic and environmental threats. The major impact in economic terms has been a massive impoverishment, especially among cattle pastoralists whose animals depend on the rich floodplain grasses along the Awash River that have almost completely been replaced by Prosopis.
The spread of Prosopis also influences social and environmental aspects beyond invaded areas. Pastoralists who lost their grazing land to Prosopis have to search for new livelihood opportunities or move to new grazing areas, which raises the risk of land conflicts with other pastoralists and farmers. Furthermore, increasing livestock densities on the remaining pasture land trigger continuing land degradation. Under these conditions, the vulnerability of pastoralists has increased and drought induced acute food insecurity has been replaced by chronic food insecurity for large parts of the pastoral population[17]. Concerning ecological aspects, Prosopis out-competes important forage species and thus reduces biodiversity that in turn has an impact on long-term forage availability and, hence, on the quality of livestock production.
Actions and approaches to manage Prosopis include for instance pod utilisation as animal feed, charcoal production and mechanical control methods. Other approaches were to calculate the Net Present Value (NPV) and Internal Rate of Return (IRR) for cotton production out of this species. Several approaches for integrated management and control mechanisms were also conducted in other countries by various institutions.
Table 1 shows in a comprised manner some results of research that has been carried out on the issue of Prosopis tackling the practical impact management.
| Who
|
When
|
What
|
Where
|
Outcome
|
| FAO and government of Niger
|
2000 – 2002
|
Mechanical control: cutting and burningBiological control: bruchid beetles, leaf-tying moths, sap-sucking psyllidsIntegrated Management: Production of Prosopis flour
|
Niger (region of Lake Chad, 300.000 ha affected)
|
Mechanical control methods are only applicable in small areas, biological control methods did not succeed, production of Prosopis flour was well accepted
|
| RSPB
|
2008
|
Recommendations for the management of Prosopis: mechanical, chemical, biological control, pasture management
|
Ascension Island
|
Implementation of recommendation is unknown
|
| Farm Africa, EIAR, UNCCD, Embassy of Norway
|
2007 – 2010
|
Management of Prosopis in the Afar Region: Uprooting, charcoal production, pod crushing, calculation of costs and benefits
|
Afar Region
|
Increased income through integrated management strategies
|
| USDA, USAID, US Forest Service
|
2012
|
Calculation of removal costs of Prosopis and investment costs (NPV and IRR) and benefits of cotton production
|
Afar Region
|
Investment on cotton production reasonable under particular circumstances
|
| HDRA, DFID, FRP, ARC LNR
|
2005
|
Cost benefit analysis of integrated management strategies, promotion of agroforestry systems
|
South Africa
|
Unknown
|
Table 1: Practical approaches to manage Prosopis
The reduction in herd sizes has repercussions on the livestock market in Ethiopia. Several factors have determined the low productivity of the livestock market in Ethiopia: civil war and violent conflict with other ethnic groups, disruption of established marketing and export systems by border conflicts with Eritrea, expansion of irrigated agriculture and large farms, poor access to the credit market, insecurity of land tenure, a land tenure system which does not allow any control in community land and recently the encroachment of invasive species, predominantly Prosopis, which are deteriorating the quality and availability of pasture land considerably. Despite sophisticated traditional pasture management systems (splitting herds, migration, sharing resources etc.) the mobile herders are not able to control the invasion to rehabilitate and reuse their traditional grazing land. The market for livestock products and especially meat is growing in the country, especially in urban areas, and Ethiopia aims at increasing its livestock production to supply these markets. It is assumed that in the past, before the invasion of Prosopis, pastoralists in the area could keep larger stocks, increasing both their income and resilience of their livelihood system.
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References
- ↑ 1.0 1.1 1.2 D. Geesing, M. Al-Khawlani, M. L. Abba (n. d.): Management of introduced Prosopis species: can economic exploitation control an invasive species?” URL: http://www.fao.org/docrep/007/y5507e/y5507e11.htm
- ↑ HDRA (2005): Controlling the spread of Prosopis in Ethiopia by its utilization, URL: http://www.gardenorganic.org.uk/pdfs/international_programme/EthiopiaProsopisBrief.pdf
- ↑ Angassa, Ayana, Oba, Gufu (2008): Effects of management and time on mechanisms of bush encroachment in southern Ethiopia. In: African Journal of Ecology, Vol. 46, Iss. 2, pp. 186-196. URL: http://dx.doi.org/10.1111/j.1365-2028.2007.00832.x and Coppock, David Layne, ed. The Borana Plateau of Southern Ethiopia: Synthesis of pastoral research, development, and change, 1980-91. Vol. 5.ILRI (aka ILCA and ILRAD), 1994.</div>
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[4] Gerber, Nicolas (2012): The Economics of Land Degradation and the Cost of Action versus Inaction, ZEF/ IFPRI.
[6] Ryan, F. (2011): US Forest Service Technical Assistance Trip to Ethiopia: Invasive Species Management: US Forest Service, cited in: Yibekal Abebe Tessema: Ecological and Economic Dimensions of the Paradoxical Invasive Species- Prosopis juliflora and Policy Challenges in Ethiopia. In: Journal of Economics and Sustainable Development, Vol.3, No.8, 2012.
[7]Pasiecznik, N.M. et al. (2001): The
Prosopis juliflora-
Prosopis pallida Complex: A Monograph, HDRA Coventry UK
[8] Wakie, Tewodros; Evangelista, Paul; Laituri, Melinda (2012): Utilization Assessment of
Prosopis juliflora in Afar Region, Ethiopia
[9] Central Statistical Agency of Ethiopia (2010)
[10] Mengistu, Alemayehu (2006): Country Pasture/Forage Resource Profiles. Ethiopia, FAO.
[12]Abiyot Berhanu and Getachew Tesfaye (2006): “THE
PROSOPIS DILEMMA, IMPACTS ON DRYLANDBIODIVERSITY AND SOME CONTROLLING METHODS“,JOURNAL OF THE DRYLANDS 1(2): 158-164, 2006
[13] Rettberg, S. and Müller-Mahn, D. (2012): Human-environment interactions: The invasion of Prosopis Juliflora in the dry lands of Northeast Ethiopia. In: Mol, L. and Sternberg, T. (Eds.): Changing deserts, Cambridge: Whitehorse Press: pp. 297-316.
[15] Rettberg, S. and Müller-Mahn, D. (2012): Human-environment interactions: The invasion of Prosopis Juliflora in the dry lands of Northeast Ethiopia. In: Mol, L. and Sternberg, T. (Eds..): Changing deserts, Cambridge: Whitehorse Press: pp. 297-316.
[16] Böhnert, Elke (2013): German Ethiopian Financial Cooperation. Territorial approach to adjusting to climate change in Eastern Ethiopia 30932. Measures to increase pastoralists’ drought resilience in the Afar National Regional State (unpublished)
[17] Müller-Mahn, D., Rettberg, S., Getachew, G. (2010): Pathways and dead ends of pastoral development among the Afar Karrayu in Ethiopia. In: European Journal for Development Research 22 (5), pp. 660-677.
