Urs Schaffner1, Eric Allan2,3, Tena Alamirew4, Ketema Bekele5, Sandra Eckert3, René Eschen1, Jema Haji5, Theo E. W. Linders1,2, Lisanework Nigatu5 and Hailu Shiferaw4,6
1CABI Switzerland, Rue des Grillons 12800, Delémont, Switzerland
2Institute of Plant Sciences, University of Bern, Switzerland
3Centre for Development and the Environment, University of Bern, Switzerland
4Water and Land Resource Centre, Addis Ababa, Ethiopia
5Department of Agricultural Economics, Haramaya University, Dire Dawa, Ethiopia
6Addis Ababa University, College of Natural Sciences, Addis Ababa, Ethiopia
Invasive alien species (IAS) not only affect ecosystems, but also human well-being. Hence, developing management strategies requires a multidisciplinary approach that is based on a clear understanding of both the ecological and the socioeconomic implications of biological invasions. We assessed the ecological and socioeconomic effects of Prosopis juliflora, a species which was deliberately introduced in Eastern Africa for the provisioning of fuelwood and for soil stabilization, but has escaped from plantations and has invaded large areas of grassland and shrubland. We found that in a lowland region in Ethiopia, Prosopis invasion significantly affects the provisioning of ecosystem services and land cover /land use dynamics. At the local scale, Prosopis invasion threatens traditional livelihood forms such as pastoralism since most of the dry-season grazing areas have already been invaded or are likely to be invaded by this tree over the next decades. At the regional scale, Prosopis was found to be a key driver of losses in ecosystem service values, a parameter increasingly recommended in decision-making. We propose that future assessments of the impacts of IAS should not only measure the effects on single indicators of ecosystem patterns or processes, but also try to further our understanding of their consequences for the social-ecological systems in the invaded range.