 One of the areas, Rack Marsh, is managed by the Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust.These six areas all have fen or swamp with large numbers of Desmoulin's whorl snail, which is listed in the British Red Data Book as it is a nationally rare and declining species.One of the areas, Eddington Marsh, also has unimproved species-rich grassland with several nationally scarce invertebrates, such as the flies "Pherbellia griseola", "Psacadina verbekei", "Platypalpus niger" and "Oxycera morrisi.