The wetland habitat at Pulborough Brooks is criss-crossed by around 14 kilometres of ditches which help us to manage the water levels on site and are home to some very special wildlife. But not all of this wildlife likes the same conditions in the ditches. To enable us to move water around the site, and to benefit species which prefer a variety of conditions, the ditches need to be managed annually. But some species would prefer plenty of vegetation which can lead to ditches getting choked up. This presents something of a dilemma....
This summer, with the support of the Heritage Lottery Fund, as part of a nationwide project 'Back from the Brink' involving a number of conservation partners, we’ll be able to have the best of both worlds. As well as clearing some of the ditches this summer – removing sediment and vegetation – we’ll be creating scalloped ditch edges or bays and dead ended ditch spurs – sections that can become refuges for very particular species like the Little Whirlpool Ramshorn Snail (Anisus vorticulus if you want to show off) who like to have plenty of aquatic vegetation around.
This tiny snail with a flattened spiral shell, who has a diameter less than 5 mm, is perhaps the rarest and most special creature on the reserve, and its presence is the reason that we have been designated as a Site of Special Scientific Interest (SSSI) and a Special Area for Conservation (SAC). In the UK it is classed as Nationally Rare and Vulnerable (IUCN) and is a European Protected Species. Pulborough Brooks reserve holds what is considered to be the second largest population in England.
Any of you who have come along to one of our pond dipping sessions will likely have encountered one of this special snail's cousins - the rather larger Ramshorn snails that inhabit most of our ponds!
Over the summer our wet grassland is at its driest which allows us to get all the habitat management work done. Our wardens carefully monitor the water levels on site and are able to make some adjustments – water can be let off the site or brought onto the site using the sluices that connect the ditches to the River Arun. In addition we can alter the water flow between ditches and then the pools on site by adjusting the ‘elbows’ on pipes that connect the ditches. You can see one of these pipes in action at the pond at the T-junction of the nature trail.
At this time of year we need it to be dry enough to enable us to complete the ditching work, but also to undertake the topping and haymaking. If it’s too boggy the tractor would get stuck and our wardens would need rescuing! At the same time, we want to make sure there is some water and in particular some nice wet mud around the pool edges that will be attractive to the migrating waders like this green sandpiper. It’s a tricky balance.
Most of the fields on the wet grassland are mown each year to ensure that they do not become overgrown with rush and to ensure that the vegetation (or sward) height is managed to be suitable both for our overwintering wildfowl (the wigeon like grazing on short turf) and for our breeding waders next spring. Creating a mosaic of grassland habitats is essential for maintaining our biodiversity.
Whilst this work is being done it will inevitably create some disturbance to wildlife but, looking on the bright side, the tractor will often disturb wading birds that would otherwise be hiding behind vegetation on the far pools!