Principe island - threats to Endemic Biodiversity
Threats to Endemic Biodiversity on Príncipe Island
The exceptional endemic biodiversity of Príncipe is under severe pressure from multiple interacting threats. Oceanic islands are inherently fragile, and the combination of a rapidly growing human population, limited land area, and introduced species has created a critical situation for many taxa.
A. Introduced Invasive Alien Species (IAS)
Invasive alien species are widely regarded as the leading cause of extinctions on islands worldwide. On Príncipe, introductions that began with human settlement in the late 15th century continue to disrupt native ecosystems.
Key invasive mammals confirmed within Príncipe Natural Park and elsewhere:
Mona monkey (Cercopithecus mona): a major predator of eggs, chicks, and adult endemic birds, including the Critically Endangered Príncipe thrush. Hunting pressure outside protected areas has displaced monkeys into the park, increasing their impact.
Feral cats (Felis catus): widespread and documented preying on the endemic Príncipe white-toothed shrew; considered a serious threat to ground-foraging and cavity-nesting forest birds.
Black rat (Rattus rattus) and brown rat (Rattus norvegicus): prey on eggs, nestlings, and possibly adult cavity-nesting birds such as the Príncipe scops-owl.
African civet (Civettictis civetta): present and potentially predatory on native reptiles, birds, and small mammals.
Invasive plants: species such as Bambusa vulgaris, Rubus rosifolius, and Lantana camara compete with native vegetation and degrade forest understorey.
Ground-nesting or ground-foraging endemic birds, including the unusually tame Príncipe thrush, show particular vulnerability to these introduced predators.
B. Direct Exploitation of Natural Resources
Unsustainable use of forest resources is widespread and intensifying with human population growth.
Hunting and trapping: despite legal protection within the Total Protection Zone of the Natural Park, illegal hunting of birds (including the Príncipe thrush) and other native wildlife continues using shotguns, snares, and traditional methods.
Overharvesting of non-timber forest products: the Obô giant land snail has experienced severe population collapse largely due to collection for food and traditional medicine. Wild honey collection often involves felling or burning host trees, and harvesting of medicinal plants threatens some species with local extinction.
Timber and firewood extraction: illegal logging and charcoal production are prevalent, especially in the drier northern part of the island.
C. Habitat Loss and Degradation from Land-Use Change
Historical and ongoing conversion of forest for agriculture remains the primary driver of habitat loss.
Historical deforestation: large-scale clearing for sugarcane, coffee, and cocoa plantations during colonial times eliminated most primary forest in accessible northern and central areas.
Current pressures: since the 1980s, land reform and population growth have led to conversion of abandoned plantations into small-scale horticulture and subsistence agriculture. Secondary forest and shade plantations now dominate the landscape.
Encroachment into protected areas: unregulated expansion of settlements and agriculture occurs even within park boundaries, notably in the Azeitona forest sector.
Indirect effects: intensified land use on steep slopes accelerates soil erosion, reduces habitat quality, and facilitates further spread of invasive species.
As a result, the most threatened endemic species (e.g., Príncipe thrush, Obô giant snail, and several forest-dependent reptiles and amphibians) are now largely confined to the remote, topographically inaccessible native forests in the southern portion of the island. Continued habitat degradation and predation pressure place these taxa at high risk of extinction in the near future unless effective management measures are strengthened.