The harbour is very shallow in places and contains a number of islands, notably Brownsea Island, the birthplace of the Scouting movement and one of the few remaining sanctuaries for indigenous red squirrels in England. The harbour, and the chalk and limestone hills of the Isle of Purbeck to the south, lie atop Western Europe's largest onshore oil field. The field, operated by Perenco from Wytch Farm, has the world's oldest continuously pumping well at Kimmeridge which has been producing oil since the early 1960s.