Before you decide to treat any invasive non-native species it is important to understand what might happen as a result. Below we have included a range of different questions that might need to be considered before you undertake invasive non-native species treatment:
What will replace the species that I am removing?
Once you remove or treat the species of concern what will take its place? For example, will it just be more of the same species regenerating from the seed bank? How long will removal works need to continue to ensure the seed bank is exhausted? After the undesirable species are removed, what other species are in the area to take their place? Is it amenity parkland, woodland or grassland? This is especially important as other invasive non-native species may be able to take their place. Consideration needs to be made of the subsequent management or action that will be needed after a species is removed.
How long term is this treatment?
How long will your efforts be effective before more of the invasive species return to the site? Many invasive species need to be considered as part of a whole catchment, or a top-down approach along a river corridor. For example, both mink (Mustela vison) and Himalayan balsam (Impatiens glandulifera) need to be considered on a larger scale to avoid re-establishment.
This is particularly important as many programmes have limited resources and you need to be clear about what you want to and can achieve before beginning.
What effect will the removal have on the biodiversity on site?
In the long term, invasive non-native species need to be managed, but consideration needs to be made to ensure that work is staged, timed or managed appropriately to minimise negative effects. For example, if nesting birds are present in a patch of an invasive species, you may need to wait until an appropriate time of year to remove the species to avoid disturbance of the birds.
As we can see, a large number of factors need to be considered, and unfortunately there are no simple answers. The questions above are a starting point for some of the factors that need to be considered before treating any invasive non-native species. Each site is different and therefore each will need to be considered separately as part of the site plan. For help with site plans, get in touch with LISI.