The earliest reserve, Zoological and Forest Reserve of Mount Kahuzi, was created on 27 July 1937 by the then Governor General of the Belgian Colonial administration. That reserve has been part of the Kahuzi-Biega National Park since November 1970. Five years later, the park was extended to cover 6000 km2. The park was declared a UNESCO World Heritage Site in 1980, under Criterion (x) for its unique habitat of rainforest and diversity of the mammal species, particularly the eastern lowland gorillas, Gorilla beringei graueri.