Rare but worrying: priority alien invasive plant species
In the case of alien invasive species, the rapid response approach plays an important role at an early invasion stage. At that time, their spread is still limited, making control up to 25 times more cost-effective than when they are already widespread. The chances of eradication are therefore highest at this early stage. However, the still limited alien species are often less well known. A good knowledge of the extent of their invasion is therefore essential for an effective rapid response.
In the RadIUS project, INBO is conducting an analysis on the occurrence of invasive alien species in nature reserves at the request of the Agency for Nature and Forest. As part of this, we mapped the presence of five currently rare plants from the European list of invasive species (the Union list). Using site visits to known locations, the risk for each species in Flanders was estimated.
The situation varies greatly from species to species.
- For Chilean rhubarb and Eastern baccharis, there does not currently seem to be any cause for concern.
- The situation is different for Common milkweed: this poisonous species is locally established and is expanding rapidly despite management.
- For American skunk-cabbage and Oriental bittersweet, there seems to be good potential for a species-specific, rapid response on the ground.
For non-native invasive species, a structured rapid response approach is desirable. This consists of drawing up contingency plans, with management approaches, responsibilities and budgets defined in advance.
Image above: Common milkwood (photo Wietse Chanet)