[5][6] Sapo National Park is located in the Upper Guinean forest ecosystem,[7] a biodiversity hotspot that has "the highest mammal species diversity of any region in the world", according to Conservation International,[8][9] and in the Western Guinean lowland forests ecoregion, according to the World Wide Fund for Nature's ecoregions classification scheme.

[16] At the time, and for twenty years, it covered an area of 1,308 km2 (505 sq mi) east of the Sinoe River and south of the Putu Mountains.

[11][14] Throughout its history, Sapo National Park has been threatened by illegal farming, hunting, logging, and mining, "all exacerbated by the country's grinding poverty"[17] and social and political instability.

However, in the early 1990s, the World Conservation Monitoring Centre reported that "[rural development projects around the park and general acceptance of its existence have helped to minimise potential conflicts.

"[15] Until the 1990s, poaching was limited due to various initiatives, funded by the United States Agency for International Development, that made local villagers stakeholders to the park's preservation.

[6][20] William Powers, a Catholic Relief Services official posted to Liberia from 1999 to 2001, noted that the park was a war-time haven for small groups of people, who scavenged for food and hunted bushmeat to survive.

The funds were reportedly pocketed by Taylor or used to secure the loyalty of various senior commanders, to arm loyalist forces embroiled in the Second Liberian Civil War (1999–2003), and to acquire mercenary fighters from South Africa.

[22][23] Liberia's Minister of Information, Reginald Goodridge, denied the allegations, noting that no evidence of logging was found during a National Geographic Society team's two-week visit to the park.

Mainly funded by the Darwin Initiative of the United Kingdom's Department for Environment, Food and Rural Affairs and the World Wildlife fund from 2000 to 2002, the objectives of the initiative were to re-establish the park's management, build support for the park among the local community, and to build Liberia's capacity in conservation management and planning.

[27] The 135 km2 (33,359 acres) East Nimba Nature Reserve (ENNR), on the border with Guinea and Côte d'Ivoire, was created at the same time to become Liberia's second protected area.

[30] Although efforts were undertaken to remove the illegal squatters, the park was not completely emptied until late August-early September 2005, and then only through the participation of conservationists, the Liberian government, and United Nations peacekeeping forces.

[35] Its tracts of forest were once continuous, but are now fragmented into blocks that are isolated from each other as a result of logging, road-building, cultivation, and human settlements.

Plant species found in the park include the legumes Tetraberlinia tubmaniana and Gilbertiodendron splendidum, and the tree Brachystegia leonensis.

The park is also home to the African civet, African fish eagle, grey parrot, giant forest hog, great blue turaco, speckle-throated otter,[40] water chevrotain, three species of pangolin, seven species of monkey (including the endangered Diana monkey[21]), crocodiles,[16] leopards,[41] bee-eaters, egrets, hornbills,[32] kingfishers, rollers, and sunbirds.

[2] According to an action plan published by the IUCN Species Survival Commission, Sapo National Park is "the only realistic choice" of a "of suitable conservation area" for the Pygmy Hippopotamus.

[45] In February 2008, automatic heat- and motion-sensing cameras set up in Sapo National Park captured the first photographs of the pygmy hippopotamus ever taken in Liberia.

[46][47] The endangered African forest elephant is also present in Sapo National park, with population estimates ranging from "as many as 500" for the early 1980s[12][20] to between 313[48] and 430[49] for the end of the decade; however, the IUCN considers the most recent surveys — both of which relied on dung counts — to be of low quality and reliability.