The disused sections of canal are the most important for the biodiversity associated with the canal system. As such, it is important that these sections are managed on a rotational basis to ensure that a high proportion have c. 50-70% open water, which allows the aquatic flora time to recover from the clearance management events. It is the balance of the different successional phases of development that is important. The currently navigable stretches of canal are mostly open water but subject to disturbance, turbidity and pollution, so this puts the emphasis on the management of the disused sections to provide suitable habitats for the biodiversity. The disused sections of the Montgomery Canal, for example, are of exceptional biodiversity importance, particularly for rare aquatic plants, e.g., floating water-plantain (Luronium natans) – a declining species which is protected under European legislation. Other species of biodiversity interest associated with this open water phase of vegetation succession are nationally rare and scarce pondweeds such as the grass-wrack pondweed (Potamogeton compressus) and the long-stalked pondweed (P. praelongus).
