Invasive Species

Invasive species are organisms that are not native to an area which have negative impacts on native species. Usually invasive species cause issues by outcompeting indigenous species for resources or altering the environment so that it no longer support their needs. These invasive, sometimes called alien, species may only directly impact one or two other species, but over time this can alter entire ecosystems. The invasive species that have been recorded inhabiting the River Thame catchment area are listed below. The data described consists of what has been surveyed across the Thame Catchment over the last 30 years but a lot more research needs to be done.

Click on any of the invasive species below to find out more information.

If you would like any more information on any of these species, please visit the GB non-native species website at

With thanks to GBNNSS & Inger Jennings (Environment Agency) for use of the photographs in the article.