Developing and applying scenarios of biological invasions (AlienScenarios)

Human agency has become the dominant force of most Earth systems, and a thorough exploration of the consequences of these pressures is needed for guiding political and societal decision making. In this context, biological invasions have emerged as a prominent feature of recent global environmental change, with substantial impacts on the environment and human livelihoods. While numbers of alien species are rising unabatedly, we still lack a thorough understanding of plausible future trajectories for the decades to come. In AlienScenarios, our consortium of seven project groups will evaluate for the first time the range of plausible trajectories of biological invasions for the 21st century at different spatial scales and for a range of taxonomic groups. We will use complementary data and approaches, and different measures of impacts of biological invasions on the environment and human societies. AlienScenarios will take advantage of several recently compiled large data sets of global alien species distributions which have partly been compiled by members of the project team. In addition, we will integrate these databases with the Alien Species First Record Database, an exhaustive database on global historic alien species accumulation rates. We will then combine the forward-looking methodology of scenario planning with advanced modeling approaches to construct plausible mid-term (2050) and long-term (2100) futures of biological invasions and their impacts taking into account uncertainties. AlienScenarios consists of seven highly integrated subprojects: In work package I we develop the qualitative narratives for plausible futures of global alien species spread in the 21st century the Alien Species Narratives (ASNs). The ASN further serves as overarching concept to parameterize quantitative models of global (WP II), continental (WP IV) and regional (WPs V, VI) futures of biological invasions, and for assessing the global impacts that future invasions may cause (WP III). Finally, in work package VII the results of the other work packages will be synthesized, and the approach and results of AlienScenarios will be discussed with and communicated to stakeholders and the wider community. For doing so, we will establish an Advisory Board that will meet three times for two-day workshops, and we will actively use a range of dissemination and outreach activities. The results of AlienScenarios will provide crucially needed insights for pro-active alien species management and policy, and they will provide the basis for exploring options for arriving at preferred futures through the adaptation of existing policies. This project will thus make an important contribution to global assessments and projections of biodiversity and ecosystem services (e.g. IPBES, CBD, Future Earth), and regional policies (e.g. European Union regulation on invasive alien species).

Biological invasions have become one of the main drivers of global change, affecting not only the environment but also human livelihoods. In contrast to the other primary drivers of biodiversity loss, such as climate change and land use change, biological invasions lack future scenarios that help us predict their development in the coming decades. In AlienScenarios, we bridge this gap and create four different and at the same time plausible future scenarios for biological invasions in the 21st century. These scenarios include different spatial scales and taxonomic groups and investigate their medium- and long-term impacts on biodiversity and human livelihoods. They were developed using established methods in scenario planning, such as participatory processes (so-called Delphi processes) and novel modeling approaches. One of the main outcomes of the project is the development of a conceptual framework for the development of such scenarios for biological invasions and their effects on the twenty-first century. Among other things, relevant steps and challenges during the process are identified and solutions are formulated. In further studies, based on expert assessments, we identified different main drivers of biological invasions, such as transport, climate change, and socio-economic changes, which influence the future impact of alien species on global biodiversity. Important insights were provided by our unique quantitative projections of the number of alien species up to 2050 worldwide for several taxonomic groups and regions. Projections show that the increase in the number of alien species will continue to increase unabated. In addition, we assessed the effectiveness of policy and management strategies for invasive alien species and assessed the future impacts of biological invasions on the environment and human livelihoods. In summary, in AlienScenarios we have quantitatively analyzed the range of plausible scenarios for the nearing of biological invasions in the 21st century, providing much-needed insights for proactive management and policies of alien species. AlienScenarios has been very successful in terms of scientific output, resulting in multiple publications, and in terms of interaction with decision-makers and the general public.