Plant invasions of protected areas in Europe: An old continent facing new problems

Abstract

Europe has a particularly long history of land protection measures, and is the region of the world with the largest number of protected areas, which has grown rapidly over the last decades. This was to a large extent due to the Natura 2000 programme of the European Union which focused on extending the existing network of legally protected areas with other habitats of conservation value. As a result, Europe has over 120,000 nationally designated protected sites (the most in the world) and 21 % of the continent area (1,228,576 km2) currently enjoys some form of legal protection. Despite these impressive statistics, the effectiveness of the existing network in protecting biodiversity is constrained by habitat fragmentation and other factors. Despite the generally high awareness of the importance of biodiversity protection in Europe, invasive alien species are not perceived as the most pressing problem by the public. This is in contrast with the fact that many of them have serious impacts on biodiversity and ecosystem functioning in protected areas. Among these, Ailanthus altissima, Fallopia taxa, Heracleum mantegazzianum, Impatiens glandulifera and Robinia pseudoacacia are considered as top invaders by managers of protected areas. Surprisingly, continent-wide rigorous data on the distribution and abundance of invasive alien species are lacking and there is an urgent need for collating checklists of alien species using standardised criteria to record their status. With the exception of very few regions such information is missing, or incomplete, based on varying criteria and scattered in grey literature and unpublished reports. To put the management on a more scientific basis the collection and curation of better data is an urgent priority; this could be done by using existing instruments of the EU as a convenient platform. As found by means of a web survey reported here, managers of protected areas in Europe are well aware of the seriousness of the problem and threats imposed by invasive plant species but are constrained in their efforts by the lack of resources, both staff and financial, and that of rigorous scientific information translated into practical guidelines.