Alder Carr is a 6.7-hectare biological Site of Special Scientific Interest in Hildersham in Cambridgeshire.

[1][2] The site is a wet valley which has alder on fen peat, a type of woodland, known as carr, which is now rare in East Anglia.

Ground flora include angelica and meadowsweet.

This habitat is very valuable to invertebrates.

[3] The site is private land with no public access.