Wealth and population key to invasive species risk, study shows Wealth and population density are the main factors driving the rise of invasive species in Europe, new EU-funded research reveals. Writing in the Proceedings of the National Academy of Sciences (PNAS), the scientists warn that tackling the invasive species problem will not be ... Wealth and population density are the main factors driving the rise of invasive species in Europe, new EU-funded research reveals. Writing in the Proceedings of the National Academy of Sciences (PNAS), the scientists warn that tackling the invasive species problem will not be easy. EU support for the research came from the DAISIE ('Delivering alien invasive species inventories for Europe') project, which is supported through the 'Sustainable development, global change and ecosystems' Thematic area of the Sixth Framework Programme (FP6), and the PRATIQUE ('Enhancements of pest risk analysis techniques') project, which is funded under the 'Food, agriculture and fisheries, and biotechnology' Theme of the Seventh Framework Programme (FP7). Earlier work from the DAISIE project revealed that around 11,000 invasive species have settled in Europe, and while the majority are harmless, around 15% cause economic damage and 15% inflict damage on ecosystems. For this latest study, the team drew on the extensive DAISIE database, which comprises the latest information on invasive species in Europe. The researchers set out to answer two questions: what factors determine the numbers of alien species in different European regions? And what is the relative importance of geographic factors compared to economic variables? The results show that wealth and population density are the two factors most strongly associated with the number of invasive species in a region. 'Invasive species are a continuing and extensive ecological crisis, and we're finding that human population and accumulated wealth are important drivers of this problem,' commented Susan Shirley of Oregon State University in the US, one of the authors of the study. 'Regional patterns of species invasions are complex, and there is still unexplained variation. But invasive species are in large part an international trade issue, and this is an important problem we have not yet come to grips with.' Human activities such as trade and transport can trigger alien invasions in a number of ways: while some species (e.g. ornamental plants and some crops) are introduced deliberately, many hitchhike on imported goods and others are imported as pets. Previous studies have highlighted the role of factors, such as climate, geography and land cover, in biological invasions. However, this study shows that these factors are less important than population density and wealth, and suggests that the impact of these secondary factors may have been overestimated in the past. 'The strong influence of economic factors on the level of invasion by alien species demonstrates that future solutions to the problem of biological invasions will be a considerable challenge,' the researchers write. 'Identifying the responsibilities of the key actors involved in trade and targeting legislation appropriately may go some way toward managing invasions.' For example, policymakers could seek to ensure that market prices for pets or ornamental plants reflect the risks and costs associated with a potential invasion, the team suggests. The problem is that the World Trade Organization does not have a mechanism to take into account the costs arising from alien invasions linked to international trade. Imposing tariffs to reflect these costs could be viewed by some as a protectionist measure. The researchers also highlight the role of transport infrastructures in facilitating the spread of invasive species. 'The environmental impact assessment of such projects should address their potential role in biological invasions and mitigate these invasions where possible,' the researchers recommend. Looking to the future, they call for urgent research to identify the specific economic factors that are most closely associated with alien invasions. 'Only if the true determinants are identified will it be possible to predict and manage alien species invasions adequately without adverse effects on other economic sectors,' the study concludes. 'A much higher precision for predicting invasions will undoubtedly help current attempts in Europe to design management strategies for alien species.'
