Cameroon became independent in 1960, and the national government retained the country's system of protected areas, and designated new ones. Until 1975, there were 9 protected areas with greater focus on the north than the south. Following the Earth Summit of Rio de Janeiro in Brazil in 1992, the number of protected areas increased substantially and were well distributed covering all the ten provinces of the country in widely differing topographic, climatic, hydrological and biological conditions. There are 20 protected reserves which include national parks, zoos, forest reserves and sanctuaries.