This post might be updated irregularly throughout the meeting. Last update 5/9/15 16:00 by Jonas Lembrechts.
Invasive species in mountain regions. An emerging hot topic with an increasing set of risks, questions and consequently papers in mountain regions. A topic that well deserves its place next to the other environmental issue as a separate session on this conference. A topic much broader than can be grasped by only one small session, but the five presentations we had gave a broad overview on the several stages of mountain invasions and the questions that can be asked.
We started with two presentations on risk assessment and the investigation of the limits and possibilities of mountain invasion, the first one brought by Marwa Halma (Alexandria University in Egypt) working on the risk of invasion by the tree Prosopis juliflora in Egypt. She showed how we can model the current and future distribution of key invaders with distribution modelling based on observations of its current location.
Next came observational and experimental research on how plants use roads and other human disturbances to invade mountain regions and how climate might not be their main limitation, even in the harsh environment of the sub(ant)arctic mountains in Northern Scandinavia and Southern Chile. This presentation was given by Jonas Lembrechts (University of Antwerp, Belgium) and he showed experimentally how invading plants need a release of competition, enough nutrients and only a fairly suitable climate to become successful.
The next presentation followed nicely with a study on the impact of several of these (mainly European) invaders, with a case study on plant-pollinator interactions in southern New Zealand (given by Christa Miller from the University of Otago). She showed how many non-native species dominate the plant-pollinator network and that many pollinators actually prefer the non-natives above the native counterparts (shown by a very elegant experiment where the pollinators were given the chance to actually choose).
Presentation number 4 brought us back to the African continent, to the invasion of Acacia meansii in the Maloti-Drakensberg mountains in South Africa (provided by Geofrey Mukwada from the University of the Free State, South Africa). He showed us the worrying contrast between the environmental impact of this species, the high and growing costs to keep the invaders under control, and the public perception of the local stakeholders, who mainly see the benefits of the species. Finding the balance between public opinion and science is clearly an important challenge for the future.
The last presenter had the important task to expand the session from plants to animals, and we thank him gratefully of warning us with his story on trout and other invasive fish in Pyrenean lakes that many other species groups invade mountains as well. The talk was given by Alexandre Miro from the Spanish Research Council (Spain) and he ended our session on a positive note, showing the beautiful results of conservation measures taken to eradicate fish invaders from the mountain lakes (mainly a change in color from troublesome green to relaxing blue).
We ended with a short discussion on the history of invaders, and when to call them as such, as well as the difficulty in providing predictions on which species will become invasive, and thus which species to manage.
Useful links: the MIREN website