What does SSSI mean? Firstly, it is a formal conservation designation. It is an area that is of particular interest to science due to the rare species of fauna or flora it contains. Flat Holm island was designated a Site of Special Scientific Interest (SSSI) in 1972. Several rare species of plant and bird are found on the island. These include the Wild Leek, which is only found in five places in the UK and a significant breeding colony of Lesser Black-backed Gulls.
It is an area that has high conservation value, and needs to be protected