Portbury Wharf lies on the land between Portishead and Royal Portbury Dock, adjacent to the Severn Estuary. Helen Mark visits the area's newest developing nature reserve and discovers how local residents are making a unique investment to their natural habitat. Look one way and you'll see a new housing construction, look the other and your eyes will be met with acres of grazing marsh land, hay meadows, and hedgerows rich in insect life stretching out to the Gordano Valley. The two are not only linked by their proximity but also by what is thought to be a first of it's kind investment arrangement. In signing up to live in the new Portbury Wharf housing development, residents are also signing up to pay an annual levy that buys them a stake in the nature reserve on their doorstep. The residents contribution allows Avon Wildlife Trust to employ a warden and a community officer to pass on wildlife knowledge and organise activities for the Portishead community. But not everyone wants to pay the levy and there's a fine line between encouraging public use and preserving natural habitats. Helen Mark meets the local residents who are getting muddy down on the reserve and keeps a look out for traces of their wildlife neighbours including the water vole - Britain's most nationally threatened animal.