How well do we understand the impacts of alien species on ecosystem services? A pan-European, cross-taxa assessment

© The Ecological Society of America www.frontiersinecology.org B invasions complicate the conservation of biodiversity and ecosystem integrity worldwide. Invasive species can threaten biological diversity in various ways, from reducing genetic variation and eroding gene pools, through the extinction of endemic species, and by altering habitat and ecosystem functioning (Hulme 2007; Table 1). Biological invasions also cause economic impacts that can be valued as financial costs, based on expert extrapolations of high-profile alien pests (Pimentel et al. 2001, 2005; Born et al. 2005; Colautti et al. 2006; Olson 2006; Lovell et al. 2006). However, ecological and economic impacts of invasions are rarely compared within or between either geographic regions or taxonomic groups. Thus, even with increasing information, we still do not know the extent to which these impacts are correlated, how taxonomic groups differ in their impacts, and which biomes suffer most. This information is essential for prioritizing management actions. Biological invasions have subtle socioeconomic consequences, which are difficult to assess using traditional monetary approaches and market-based models (Binimelis et al. 2007). To address this added complexity, we analyzed impacts described in the Millennium Ecosystem Assessment framework (MA 2005), in order to link ecological and economic impacts, by assuming that the effect of any ecological change influences ecosystem services and, in turn, human well-being. The ecosystem services approach attributes values to ecosystem processes, as the basis for all human needs. Ecosystem services are classified into four categories: “supporting” (ie major ecosystem resources and energy cycles), “provisioning” (ie production of goods), “regulating” (ie maintenance of ecosystem processes), and “cultural” (ie non-material benefits). The ecosystem assessment approach requires multidisciplinary collaboration in environmental management (Meyerson REVIEWS REVIEWS REVIEWS