Projecting trends in plant invasions in Europe under different scenarios of future land-use change: policy orientations will not reduce invasions

Aim The recent discovery of the consistent patterns in plant invasions in habitat types across different climatic regions made it possible to produce a European map of plant invasions. Parallel research led to the formulation of integrated scenarios of future socio-economic development in Europe, which were used to project land-use patterns in Europe for 2020, 2050 and 2080. Here we integrate these two research lines and produce the first spatially explicit projections of plant invasions in Europe for these three target years. Location European Union, Norway and Switzerland. Methods We used vegetation plot data from southern, central and north-western Europe to quantify mean local levels of invasion by neophytes (post-1500 alien plants) for forest, grassland, urban, arable and abandoned land. We projected these values on the scenarios of future land-use for the three target years and constructed maps of future plant invasions under three socio-economic scenarios assuming (1) deregulation, (2) continuation of current policies with standing regulations and (3) shift towards sustainable development. Results Under all scenarios an increase in the level of invasion was projected especially for north-western and northern Europe, and a decrease for some agricultural areas of eastern Europe where abandonment of agricultural land is expected. However, a net increase in the level of invasion over Europe is projected under all scenarios. Main conclusions The polarization between more and less invaded regions is likely to increase if future policies are oriented on deregulation. However, an implementation of sustainability policies would not automatically restrict the spread of alien plants. On the contrary, such policies might increase invasions by supporting agriculture and associated invasion-prone land use in less productive areas. Therefore, proactive strategies to combat invasive alien plants will be needed no matter which policies will be adopted in the future.