Habitat loss is defined as the total destruction of natural ecosystems, an inevitable consequence of expanding human populations and human activities. Island biogeography theory offers a good explanation of why habitat loss leads to species extinction.
Using oceanic islands as a model system, one of the main predictions of the theory is that larger islands have more species. Empirical evidence strongly supports this observation. For example, large African islands generally support more bird species than small islands.
In addition, 62 of 79 (63%) sub-Saharan African species that have become extinct in recent centuries were confined to oceanic islands rather than the mainland which actually functions as a very large island. The primary threat to Africa’sbiodiversity today is habitat loss and degradation.
The size of the area greatly influences species richness, as evidenced by the richness of bird species on several important volcanic islands around Africa. This observation, known as the species-area relationship, explains why habitat loss is so devastating to biodiversity: the more we reduce the more habitat left for species to live in, and the more extinctions we will see in the years to come.
This is especially true when trying to protect species that have large home ranges and/or are found in low densities: they can only live in areas of habitat large enough to maintain viable populations. Observations of eradications in habitat areas of varying sizes support this claim.
For example, researchers found that nearly 50% of forest bird species in Ghana are sensitive to habitat size, with 25% of species never found in forest areas smaller than 0.1 km2. .A Ghanaian species that seems particularly sensitive to habitat size is the green bulb icterino (Phyllastrephus icterinus, LC); Due to habitat loss, this once common species declined by 90% over the 15-year period of one study.
It is important to understand that species live in inconspicuous ecosystems destroyed, it may also suffer the effects of habitat loss and as a result, the population experiences a decline. Indeed, habitat loss often manifests itself, at least initially, in less visible but equally threatening habitat degradation.
For example, disturbances such as overgrazing do not immediately change the organization of dominant plants and other structural features of an ecological community. First, barely noticeable, some sensitive habitat specialists disappear, unable to cope with high levels of grazing. Soon, invasive species that can tolerate trampling start occupying niches left open by uprooted susceptible species.
Eventually, when livestock eat the last remaining edible bits of palatable plants not choked out by invasive species, all that remains of the once productive pasture is a field full of dense, unsightly, overgrown shrubs
The remaining populations of the pygmy hippopotamus (Choeropsis liberoensis, EN) are mainly found in the western limit African rainforests spanning Côte d’Ivoire, Guinea, Liberia, and Sierra Leone. An elusive animal, little is known about the distribution, population status, and ecology of the pygmy hippopotamus.
The number of pygmy hippos is currently estimated at fewer than 2,500 individuals across its range, with the expected further decline due to agricultural expansion, logging, development, and hunting. In Liberia, pygmy hippo populations are found in major forest blocks in the southeast and northwest which are separated by an area of degraded land with high human density.
The Southeast Forest Block is made up of several large blocks of national, municipal, and protected forests fragmented by logging roads and concessions. Although populations are well documented in protected areas, recent reports indicate that populations also exist outside of officially protected forests.
The creation and management of forest corridors linking key habitats is, therefore, a conservation priority. In recent years, huge investments in agriculture, logging, and mining have increased the pressure on forests for conversion by increasing human settlements and access roads. This has led to weak law enforcement in Liberia’s protected areas and limited operational capacity increased incursion of illegal activities, such as poaching and mining into these critical habitats.
Sapo National Park, the only national park in Liberia and the second largest in West Africa in Côte d’Ivoire is considered a stronghold for the species. However, the number of pygmy hippos remains low. Recent efforts to save Liberia’s declining forests have resulted in an increase in national and international NGO activities and the formation of cross-border collaborative initiatives.
The Liberian and Guinean governments have also initiated a bilateral agreement for the conservation and sustainable management of the transboundary forest landscape. Agricultural investments have also evolved to promote public-private partnerships in green growth and community-based forest protection initiatives.
Wildlife & Flora International (FFI) has been working in Liberia since 1997 focusing on the pygmy hippopotamus as a flagship species. These efforts have contributed to a better knowledge of the species in Liberia. Effective law enforcement across borders and within protected areas will be key to safeguarding and increasing the number of remaining pygmy hippos, while raising awareness.
Collaborative forest management and national/regional policies will be needed to reduce deforestation to protect habitats for pygmy hippo populations to thrive.