Tropical32-kannet- 3.4.2007 09:23 Page 1 C M Y CM MY CY CMY K TROPICAL FORESTRY REPORTS 32 FORESTRY TROPICAL UNIVERSITY OF HELSINKI UNIVERSITY OF HELSINKI Viikki Tropical Resources Institute Viikki Tropical Resources Institute VITRI VITRI TROPICAL FORESTRY REPORTS No. 31 Luukkanen, O., Katila, P., Elsiddig, E., Glover, E. K., Sharawi, H. and Elfadl, M. 2006. TROPICAL FORESTRY REPORTS Partnership between Public and Private Actors in Forest-Sector Development. No. 32 Laxén, J. 2007. Is prosopis a curse or a blessing? – An ecological-economic 32 analysis of an invasive alien tree species in Sudan. Doctoral thesis. analysis of an invasive alien tree species in Sudan alien tree analysis of an invasive a curse or blessing? – An ecological-economicIs prosopis ISBN 978-952-10-3891-4 (paperback) Jörn Laxén ISBN 978-952-10-3892-1 (PDF) ISSN 0786-8170 Is prosopis a curse or a blessing? – An ecological-economic Helsinki 2007 analysis of an invasive alien tree species in Sudan Hakapaino Oy Composite Tropical32-sis.kan 11.4.2007 12:26 Page 1 C M Y CM MY CY CMY K UNIVERSITY OF HELSINKI No. 15 Mustafa, A. F. 1997. Regeneration of Acacia seyal forests on the dryland of the Sudan clay plain. Doctoral thesis. Viikki Tropical Resources Institute No. 16 El Fadl, M. A. 1997. Management of Prosopis juliflora for use in agroforestry systems VITRI in the Sudan. Doctoral thesis. No. 17 Kaarakka, V. & Holmberg, G. 1999. Environmental conflicts and development co- operation with special reference to conservation and sustainable management of tropical forests. No. 18 Li, C. 1999. Drought adaptation and genetic diversity in Eucalyptus microtheca. Doctoral thesis (limited distribution). No. 19 Suoheimo, J. 1999. Natural regeneration of sal (Shorea robusta) in the Terai region, Nepal. Doctoral thesis. No. 20 Koskela, J. 2000. Growth of grass-stage Pinus merkusii seedlings as affected by TROPICAL FORESTRY REPORTS interaction between structure and function. Doctoral thesis (limited distribution). No. 21 Otsamo, R. 2000. Integration of indigenous tree species into fast-growing forest plantations on Imperata grasslands in Indonesia - Silvicultural solutions and their TROPICAL FORESTRY REPORTS contains (mainly in English) doctoral ecological and practical implications. Doctoral thesis (limited distribution). dissertations, original research reports, seminar proceedings and research No. 22 Koskela, J., Nygren, P., Berninger, F. & Luukkanen, O. 2000. Implications of project reviews connected with Finnish-supported international the Kyoto Protocol for tropical forest management and land use: prospects and pitfalls. development cooperation in the field of forestry. No. 23 Otsamo, A. 2001. Forest plantations on Imperata grassland in Indonesia – Establishment, silviculture and utilization potential. Doctoral thesis Publisher Viikki Tropical Resources Institute (VITRI) (limited distribution). P.O. Box 27, FI-00014 University of Helsinki, Finland No. 24 Eshetu Yirdaw 2002. Restoration of the native woody-species diversity, using (address for exchange, sale and inquiries) plantation species as foster trees, in the degraded highlands of Ethiopia. Doctoral thesis. Editor Olavi Luukkanen No. 25 Appiah, M. 2003. Domestication of an indigenous tropical forest tree: Silvicultural and socio-economic studies on Iroko (Milicia excelsa) in Ghana. Telephone +358-9-191 58643 Doctoral thesis. Telefax +358-9-191 58646 No. 26 Gaafar Mohamed, A. 2005. Improvement of traditional Acacia senegal agroforestry: E-mail [email protected] Ecophysiological characteristics as indicators for tree-crop interaction in western Sudan Website www.mm.helsinki.fi/mmeko/vitri Doctoral thesis. No. 27 Glover, Edinam K. 2005. Tropical dryland rehabilitation: Case study on participatory forest management in Gedaref, Sudan. Doctoral thesis. Cover Design Lesley Quagraine No. 28 Hares, M. 2006. Community forestry and environmental literacy in northern Thailand: Towards collaborative natural resource management and conservation. Doctoral thesis. Suggested reference abbreviation: No. 29 Eskonheimo A. 2006. Women, environmental changes and forestry-related development: Univ. Helsinki Tropic. Forest. Rep. Gender-affected roles of rural people in land degradation and environmental rehabilitation in a dry region of Sudan. Doctoral thesis. No. 30 Raddad, E.Y.A. 2006. Tropical dryland agroforestry on clay soils: Analysis of systems based on Acacia senegal in the Blue Nile region, Sudan. Doctoral thesis (limited distribution). Composite Is prosopis a curse or a blessing? – An ecological-economic analysis of an invasive alien tree species in Sudan Jörn Laxén Academic dissertation To be presented, with the permission of the Faculty of Agriculture and Forestry of the University of Helsinki, for public discussion in Auditorium XII of the University Main Building, Fabianinkatu 34, on Friday 27 April at 12 o’clock noon Helsinki 2007 Supervisors: Professor Olavi Luukkanen Director Viikki Tropical Resources Institute (VITRI) Department of Forest Ecology University of Helsinki Helsinki, Finland Professor John Sumelius Department of Economics and Management University of Helsinki Helsinki, Finland Reviewers: Professor Jussi Uusivuori Finnish Forest Research Institute (METLA) Helsinki, Finland Ph.D. Marko Katila Economic Adviser Ministry for Foreign Affairs Helsinki, Finland Opponent: Professor Arild Vatn Norwegian University of Life Sciences (UMB) Aas, Norway 2 ABSTRACT The overall aim of this work was to develop scientifically verified and realistic solutions for the quantification of impacts and a further ecological (environmental) economic valuation of benefits and social costs of prosopis (Prosopis juliflora) in Sudan. A Presidential Decree from 1995 to eradicate the prosopis tree from everywhere in Sudan due to its conceived overall net detrimental impacts constituted a demanding challenge to investigate whether this view on the species is true or false. This is a long-standing issue of hot debates in numerous other countries in the tropics and sub-tropics as well. The research methodology primarily, consisted of a problem-based approach that emphasized economic analyses which utilized, where available, the market economic values at two case study sites framed inside the New Halfa and the Gandato Irrigation Schemes, respectively. Additionally, the derivation of non-market values was captured using ecological economic tools, so as to reach a deeper understanding on how prosopis impacts on the environment and on the human well-being at the two study sites. The main data collection in the New Halfa Scheme framed area in Kassala State was first conducted as four separate household surveys (totally with 110 sample households) for the tenant farmers, the western and the eastern Sudanese landless people, as well as for the nomad population group, respectively. The latter three comprised several ethnic groups. Due to the complexity caused by a diversity of the population groups, the main aim at New Halfa was to study the magnitude of environmental economic benefits and costs, derived from the invasion of prosopis in a large agricultural irrigation scheme on clay soils. A comparison was also made between a prosopis- invaded framed area and an area totally devoid of prosopis in the same scheme. In New Halfa, there was a distinct and slowly decreasing trend from the poorest towards the richest households in the dependence on prosopis among the western and eastern Sudanese landless groups as well as among the nomads. For the western Sudanese landless population, prosopis was a substantial cash income source, and for all landless groups it was important for the subsistence income in the form of free-grazing forage, wood energy, and construction materials. Although many landless households considered themselves as farmer families, their income related to prosopis was larger than their crop cultivation income. In contrast, for the tenant farmers prosopis considerably reduced the profits from crop cultivation, due to the increased expenses for ploughing the prosopis- invaded irrigated fields and for the maintenance of irrigation canals. It also caused costs for employing labour for weeding and the cutting of trees, and in the form of thorn injuries that sometimes needed medical attendance. However, the tenant farmers also had benefits from the prosopis-based free-grazing forage and from fuelwood. Although prosopis products could be obtained free of charge directly by the households, many of them voluntarily chose to purchase charcoal, fuelwood and poles. The valuation in the New Halfa Scheme identified partly different benefits and costs as compared to the Gandato Scheme, and the results are not as clearly in favour of prosopis, although a Benefit/Cost Ratio of 2.1 could be concluded for this area. There were several reasons for the different situation in benefits and costs derived from prosopis in the New Halfa Scheme as compared to the Gandato Scheme: (a) a more complex population background in New Halfa, leading to varying benefits and detriments for each group; (b) prosopis actually growing inside the agriculture scheme, which was not a preferred situation; (c) a soil which mainly consisted of clay; thus the potential beneficial impacts from protection from sand invasion 3 were not needed; (d) other tree species which could be grown inside the scheme but which would have needed more tending than prosopis; and (e) prosopis causing much more detrimental impacts on the operational costs for agriculture in this scheme as compared