When IAS recolonise managed areas
Once well-established in the new environment, invasive alien species (IAS) begin to spread and colonise areas. As they start to move around, exchange of individuals between different populations occurs as well. As a result, there is an important risk for areas where successful management actions such as eradication were performed to be reinvaded.
The management of IAS is, indeed, highly challenging. While the eradication of some terrestrial invasive alien species has been successful, aquatic and riparian biological invasions are often extremely complex to control. The continuity and connexion of aquatic environments facilitate invasions and reinvasions to occur, making management efforts potentially ineffective.
The current management of invasive aquatic and riparian species gives, however, little consideration to the connectivity of running water bodies and the upstream-downstream dynamics that facilitate species dispersal. As a result, invasions and reinvasions are often observed from upstream areas, making management actions unsustainable.
To tackle this issue, there is a need to take into account the risk of dispersal from one site to another. In the case of river management actions, upstream areas must, for instance, be prioritised over downstream ones.