The context of the symposium

Numerous species of animals, plants, bacteria and fungi have been introduced to new environments along with human colonization and activity, both intentionally and unintentionally. These alien species have had various unexpected and usually detrimental impacts on the original fauna and flora. Alien introductions may result in reductions of population sizes and distributions of native species, and in extreme cases, also extinctions of natives. The most dramatic and well-known effects have occurred on oceanic islands, where the arrival of novel mammalian predators has resulted in many extinctions of native, predator-naïve prey species. Large-scale effects have also been reported in semi-enclosed seas and lakes.

Alien species are affecting ecosystems worldwide, and, following habitat destruction, they are considered the second largest threat to biodiversity in both aquatic and terrestrial ecosystems. Many aliens survive only in human disturbed environments, while others are also able to invade natural habitats. However, global warming may well enhance the survival of novel aliens in high latitudes. Also the expanding global trade increases the risk of new introductions, calling for improved control in transportation. The economic impacts of alien species in e.g. agriculture and forestry are enormous and will continue to increase in the future.

The objective of the 5th Symposium was to provide a forum for a multi- and interdisciplinary discussion of threats and benefits related to alien species: impacts on biotic communities in aquatic and terrestial ecosystems, the economic effects of aliens, the effect of climate change and global trade on aliens, biorisks brought by aliens, and visions for the future. To our knowledge this was the first alien species symposium in the Baltic Sea area with such a wide approach. In addition to researchers, the Symposium was also intended for students, decision makers, NGOs and media. The topics were addressed in separate sessions, featuring leading Finnish and international scientists and experts as invited speakers. The poster session of the Symposium was open to anyone interested in presenting research related to the topics.

During 17 - 21 January 2007 the participants had free entry to the exhibition sponsored by Maj and Tor Nessling Foundation and hosted by the Turku Biological Museum: "Aliens - muukalaisia luonnossa" ("Aliens in nature"). The exhibition is in Finnish and Swedish but a short summary in English is provided. The exhibition will be in Turku Biological Museum till the end of May 2007.

Photos from left: P. Salo, J. Sarvala, E. Leppäkoski, E. Oksanen/Metla