Regarding the fencing that I understand relatively recently appeared along the Billy Trail adjacent to the Sinah Field that is currently under Development Planning Application App/18/00724, this is relevant information:
The land is owned by Hayling Island Builders Ltd and they are selling to Barratt, with whom they have an association. They are allowed to fence off the Billy Trail, in fact it was a requirement in the mitigation on this and the Oysters development to prevent dog walkers and their dogs scaring off the birds and stopping their flight path over the RSPB fields. Residents noted that this supposed mitigation was not put in place whilst the Oysters was being built so that the wildlife was not thereby protected as had been the undertaking. It would appear that the fencing is now to protect the area for development.