Management has started

Ready for the field: LIFE RIPARIAS management actions have started 

Have you ever heard of floating pennywort, parrot’s feather or water primrose? These are some examples of exotic species that have been invading our ponds, canals, and other waterways for many years, significantly altering aquatic ecosystems. It is now time for action.

What’s going on in the Walloon Region?

In April 2023, our dedicated field team started the first of many management actions in the field against those invasive alien species. In the Senne sub-basin, the team started by clearing a pond of approximately 300 m2 that was entirely covered with parrot’s feather (Myriophyllum aquaticum). They managed to remove a total volume of 8 m3 of plant material.

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The second action involved a water body of approximately 1000 m2, heavily silted and almost completely invaded by floating pennywort (Hydrocotyle ranunculoides). Clearing the pond was labour intensive as the plant population had to be manually removed. It took a team of 5 people and no less than 5 full days to get through the management of this population. With the addition of new workers to help with seasonal field management, more challenging sites were tackled, including a population of water primrose (Ludwigia grandiflora) at a beaver dam in the Marache River, located in Court-Saint-Etienne, populations of floating pennywort (Hydrocotyle ranunculoides) in multiple water bodies within the Argenteuil Estate in Waterloo and the management of Himalayan balsam (Impatiens glandulifera) along the banks of the Hain and Lasne rivers.

obj 770 In the Dyle sub-basin, the first and most significant project was conducted in a water body of about 1500 m2, located in Villers-la-Ville. Two full days of work were necessary to remove the whole population of parrot’s feather, covering about 30% of the total surface area. In the same municipality, a small pond of approximately 300 m2 was entirely invaded by both parrot’s feather (Myriophyllum aquaticum) and floating pennywort (Hydrocotyle ranunculoides), threatening the biodiversity of this beautiful place. Two others but less invaded sites were also managed in the municipalities of Grez-Doiceau and Genappe.


What’s going on in the Flemish Region?

This year, the management of widespread species in Flanders focused on Himalayan balsam (Impatiens glandulifera) in the Laan and Ijse river. The infested parts of the rivers were cleared through manual removal for the best results. A few ponds owned by the Flemish government and invaded with water primrose (Ludwigia grandiflora) and parrot’s feather (Myriophyllum aquaticum) were also managed. In addition, some isolated plants and populations of giant hogweed (Heracleum mantegazzianum) were manually removed to prevent spread and mitigate health risks. In the meantime, all new observations are closely monitored through the early alert tool, so a rapid management response in priority areas is possible.

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What’s going on in the Brussels-Capital Region?

In Brussels, small spots of giant hogweed (Heracleum mantegazzianum) were managed along with different populations of Himalayan balsam (Impatiens glandulifera) that had established along small creeks and streams in the Pede-valley. Additionally, one population of American skunk cabbage (Lysichiton americanus) was subject to management for complete eradication along the banks of the Woluwe river while 2 others were assessed for management and will be soon eradicated. Further management actions for parrot’s feather (Myriophyllum aquaticum) and Manchurian wildrice (Zizania latifolia) are being planned for after the summer as this period is considered the most suitable for carrying out these actions. To address Zizania latifolia population, which is known for its strongly developed root systems, heavy-duty equipment will be employed to mechanically remove the plants and their rhizomes from the ponds they have invaded.

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What’s to come?

All the sites that were managed in the 3 Regions will be monitored and regulary visited throughout the duration of the LIFE RIPARIAS project to remove regrowth and assess the success or failure of the actions. More sites and species will be managed in the coming years in the 3 Regions, as it is only the beginning of a long process.


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This small population of water primrose (Ludwigia grandiflora) was found in the Flemish Region during a monitoring visit for crayfish. It was rapidly reported to the local management team (Sport Vlaanderen), who then quickly managed the population in summer 2022. In June 2023, a second intervention was necessary and organised by the local management team as some regrowth had occurred.