It covers 55 square miles ( 140 km ) and is centred on Braunton Burrows , the largest sand dune system ( psammosere ) in England .
North Devon 's Biosphere Reserve is a UNESCO - designated biosphere reserve in North Devon .
Biosphere Reserve covers 55 square miles ( 140 km ) and is centred on Braunton Burrows , the largest sand dune system ( psammosere ) in England .
North Devon 's Biosphere Reserve is a UNESCO - designated biosphere reserve in North Devon .