There are 53 Sites of Special Scientific Interest of which the largest are Loch an Duin , North Uist at 15,100 hectares ( 37,000 acres ) and North Harris , which is 12,700 hectares ( 31,000 acres ) in extent .
There are 53 Sites of Special Scientific Interest ( SSSI ) of which the largest are Loch an Duin , North Uist at 15,100 hectares ( 37,000 acres ) and North Harris , which is 12,700 hectares ( 31,000 acres ) in extent .