Symposium - Exotic species in nature reserves

4-hour symposium on 5 September 2009 organised by CML on ECCB 2009 - 2nd European Congress of Conservation Biology “Conservation biology and beyond: from science to practice”, Praag, 1-5 September 2009


Exotic species are one important part of biological pollution of our planet. The other part is the genetic pollution by introduction of foreign populations, e.g. the re-introduction of threatened species. In this symposium the focus is on exotic species. A number of exotic species exhibit an invasive and aggressive behavior and these are considered an important threat to biodiversity and to ecosystem services. Most exotic species can be found in disturbed, anthropogenic habitats, like urban and agricultural areas. Only a minority of exotic species manage to colonize more natural habitats, a.o.  nature reserves.

Some exotic species have been introduced a very long time ago, so most people seldom acknowledge these exotic species as a threat, but sometimes even as a valuable part of the ecosystem. One example is the exotic large, yellow-flowered Evening primroses (Oenothera spec.) from North-America are considered by many people, including biologists and nature conservationists, as a valuable addition to the indigenous flora of the dunal areas in the Netherlands. Other exotic species have been purposely planted at a large scale for forestry goals in natural areas, and some of these species showed very strong expansions, like the Rum cherry (Prunus serotina), White poplar (Populus alba), and the Townsend’s Cordgrass (Spartina x townsendi). Only a minor number of other exotic species have managed to invade the natural areas or nature reserves.

In this symposium the presence and history of exotic species in nature reserves throughout Europe, the effects of these exotic species on the native species and on the ecosystem and the management of exotic species in nature reserves are presented and discussed.

There are some of the questions to be treated during this symposium:

  • Why are some exotic species highly valued and present on the national Red Lists?
  • Why are there so few exotic species present in natural areas in comparison with urban and agricultural areas?
  • Do these exotic species in nature reserves have other characteristics then those in non-natural areas?
  • How much do we actually know of effects on native biodiversity, and these effects being adequately monitored?
  • And how to manage invasive exotic species in nature reserves, without damaging the present natural values and landscapes?


Organisation: Wil L.M. Tamis, CML, Leiden



First part 10.30-12.30
  Introduction by the chair

Lecture 1    Management of the Black Cherry (Prunus serotina) in the dunal region in the Netherlands
(Antje Ehrenburgh, Waternet, The Netherlands)

Lecture 2 Long term population dynamics and management of the Black cherry (Prunus serotina) in natural forests on sandy soils in Belgium
(Margot Vanhellemont, Kris Verheyen, Lab. Forestry Ghent University, Belgium.)

Lecture 3 The Purple chokeberry (Aronia x prunifolia), a problem in lowland peat swamp nature reserves in the Netherlands?
(Wil Tamis, Institute of Environmental Sciences, University Leiden (CML), The Netherlands)

Lecture 4 Rosa rugosa, an invasive species in the coastal dunes of Germany
(Maike Isermann, Anna Jürgens, Martin Diekmann, Ingo Kowarik, Dept. Vegetation Ecology and Conservation Biology University Bremen, Dept. Ecosystem Science and Plant Ecology TU Berlin, Germany)

Lecture 5 Defending the boundaries: the threat to coastal dunes of invasive exotics from adjacent gardens
(Sally Edmondson, Liverpool Hope University, Ireland)

Lecture 6 A review of alien species in the National Parks of Austria
(Wolfgang Rabitsch, Umweltbundesamt, Austria)

Lunch                  12.30-14.00

Second part 14.00-16.00
Lecture 7 Impact of exotic species on crayfish conservation in the Czech Republic
(Zdenek Duriš, A.Petrusek, P.Kozák a.o., Dep. Biology, University Ostrava, Czech Republic)

Lecture 8 Introductions of amphipod crustaceans and consequences for native communities in the north-western Russia
(Nadezhda Berezina, Zoological Institute RAS, Russia)

Lecture 9 The relentless tide of introduced alien species into the Wadden Sea
(Karsten Reise, Alfred Wegener Institute for Polar and Marine Research, Germany)

Lecture 10 Invasive Species do not ask for green cards: How can biological invasions be regulated in European conservation legislation and policy?
(Frank Klingenstein, Federal Agency for Nature Conservation, Germany)

11 Discussion and concluding remarks on this symposium

Last Modified: 02-09-2009