Policies slow biological invasions in Europe, but legacies still matter

Biological invasions are a main cause of biodiversity loss, prompting international agreements and national policies aimed at preventing and managing the introduction, establishment, spread, and impacts of alien species. However, whether these measures have effectively reduced invasions remains uncertain. In this study, we compared the absolute number of established alien species and changes in invasion rates, accounting for sampling effort and invasion timing, across European Union (EU) countries and the United Kingdom (UK) with the number and types of policies implemented. Policy effects were analyzed alongside other invasion drivers, including trade, climate, and geography. We demonstrate for the first time that invasive species policies within the EU and the UK had significant protective effects. Notably, these effects were evident only when examining changes in invasion rates, emphasizing the need to consider invasion dynamics and policy timing. These results should encourage countries to continue managing invasions and contribute to refining strategies for managing alien species.