Snowdonia has a particularly high number of protected sites in respect of its diverse ecology; nearly 20% of its total area is protected by UK and European law. Half of that area was set aside by the government under the European Habitats Directive as a Special Area of Conservation. There are a large number of Sites of special scientific interest (or 'SSSIs'), designated both for fauna and flora but also in some cases for geology. Nineteen of these sites are managed as national nature reserves by Natural Resources Wales. The park also contains twelve Special Areas of Conservation (or 'SACs'), three Special Protection Areas (or 'SPAs') and three Ramsar sites. Some are wholly within the park boundaries, others straddle it to various degrees.