The Ouse Washes collectively form a wetland of international importance, extending for 31km between Earith at the southern end and Welmore Lake Sluice at the northern end. The Royal Society for the Protection of Birds and the Cambridgeshire Wildlife Trust run a combined reserve of 1,277ha (over 3,000 acres) in the southern part of the Washes, whilst the Wildfowl and Wetlands Trust owns 368ha in the northern section (in Norfolk).