Source to Sea – Avon Valley

Avon Valley by Mark EmeryAvon Valley by Mark Emery

The River Avon and its tributaries form the largest chalk river system in England. A haven for rare and threatened wildlife, the river is of international importance and has been designated as a Special Area of Conservation and a Site of Special Scientific Interest.

Giant hogweed by Catherine ChattersThis partnership project is turning the tide against the spread of invasive non-native plants in the Avon Valley, particularly along watercourses and stunning wetland habitats.

Along the length of the River Avon we are working to remove non-native plants that disrupt the ecosystem and threaten native plants and wildlife. By controlling the spread of invasive plants such as Himalayan balsam and creeping water primrose we can ensure that vulnerable environments become bigger, better and more joined up with other habitats.

Non-native plants are species which have been imported from abroad and landowners incorporate them in their gardens or pond. The plants then sometimes manage to spread beyond the garden fence and into the wild. Because these non-native plants don’t suffer from the same competition and diseases in their native range, they can be free to grow rapidly, often crowding out our native species.

The Avon Valley is on the western boundary of the New Forest. View the map of the Source to Sea Project area.


Himalayan balsamPlants might seem harmless, but the effects of invasive plants can be dramatic and wide-ranging. Invading plants can dominate native species, which in turn can affect the insects which feed on them. An entire ecosystem can be disrupted by the influx of non-native plants – potentially causing a loss of diversity.

Invasive plants can therefore impact on wildlife in and around our rivers, such as trout, salmon and crayfish, while also reducing food stocks for otter, kingfisher, lamprey and water vole. Rare species such as Desmoulin’s whorl snail and water crowfoot are also threatened by these dangerous invaders.

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Project partners

Source to Sea is a partnership project between Hampshire & Isle of Wight Wildlife Trust, Wiltshire Wildlife Trust, Dorset Wildlife Trust and the Environment Agency.