Since the early days of settlement by Portuguese colonists in the 17th century, with the cultivation of sugarcane (Saccharum officinarum), the use of biological resources has been closely bound with the occupation of S. Tomé and Príncipe. The sustainable use of the country’s biological diversity, to have local communities profit from it and thus combat poverty, is directly tied to its preservation.
Cocoa, Theobroma cacao (the country’s main export) and coffee, Coffea spp., throughout the 18th and 19th centuries, require maintenance of the forest mantle for shading. The shade forests that colonized the lowlands, which are choice agricultural terrain in São Tomé and Príncipe, enjoy an internacional reputation, as they are amenable to the preservation of tropical soil under insular conditions and the maintenance of a few forest essences.
The flora of S. Tomé and Príncipe has also drawn attention from researchers as Júlio Henriques and Arthur Exell, respectively a professor with the University of Coimbra and a scientist with the British Museum.
F. Welwitshi in 1853, and then C. Barter in 1858 and G. Mann in 1861 also gathered specimens leading to the discovery of species thereto unknown.
Auguste Chevalier visited S. Tomé in 1905, and in 1956 Théodore Monod climbed the peaks of S. Tomé and of Príncipe, culling rare endemic specimens.
Joaquim Espírito Santo discovered new species in the 1960’s and 1970’s, and Herder Lains e Silva undertook new research and classification of the country’s flora.
Research has shown that, of the four islands on the Gulf of Guinea, Bioko, Príncipe, São Tomé and Pagalu, the Santomean archipelago presents the richest diversity of flora, with high rates of endemism.
In the past, economic goals superseded conservation efforts.
Thus the country’s biodiversity has been hampered by man since the late 15th century (Hodges and Newitt, 1988), especially in the lowlands where sugarcane, cocoa and coffee were grown. Several exotic species have been introduced (Monod, 1960), disrupting equilibrium.
Human pressure on the archipelago’s natural resources, and especially on the forest, takes a toll on biodiversity.
Vegetal cover takes the most damage. Wood and plant species are indiscriminately harvested around and in Park Obô. Agriculture, the introduction of exotic species or other unsound practices cause considerable harm. Over the past few years, biological diversity has waned in the archipelago’s ecosystems. The standard of living has gone down for the communities that depended on harmed species, and so these communities now struggle with extreme poverty.
Non-sustainable practices are not inevitable. They arise from poor knowledge of flora and the intrinsic relationships it adheres to. The country needs effective research mechanisms to improve knowledge on the country’s flora and the means to disseminate useful knowledge among the communities. The development and improvement of the Bom Sucesso Botanical Garden, under the ECOFAC project, is one of the ways to fill the lack.
The preservation of forest mantles is relevant to the country’s agrarian system (regulation of rainfall, insolation and evapotranspiration), protection of hydrographic basins, protection of soil against erosion, recycling nutrients and the reconstitution of natural fertility in soils. Furthermore, as other rainforests throughout the world, Santomean forests may function as carbon dioxide regulators, contributing towards the management of climate change.
2.4 BIODIVERSITY ON LAND
The country being cut off from the African mainland, its biological diversity is unique. Isolation has brought about a high number of endemic flora and fauna (see tables 1, 2, 6 and 9 in the annex).
The scientific world recognizes this diversity and considers the Santomean rainforest as second in terms of the preservation of avian fauna, among 75 African forests (World Bank 1993).
The flora of São Tomé and Príncipe is also remarkable for its high rate of endemism. The island of S. Tomé has one endemic genus and 87 endemic species. Príncipe has one endemic genus and 32 endemic species (ENPAB forests 2002).
2.5 Main ecosystems and habitats in the country
Biodiversity in São Tomé and Príncipe reveals a large variety of ecosystems in the archipelago: Natural ecosystems (forests, mangroves, inland waters, coastal and marine) and modified ecosystems (secondary forests and old plantations, shade forests, savannahs, dry forests).
An ecosystem-based approach to the biological wealth of São Tomé and Príncipe is still the most pragmatic way to build a diagnosis on biodiversity in the country and recommend specific measures for preservation and sustainable use. For the purposes of this paper, 4 main ecosystems have been defined:
Scheme 3: Types of ecosystem in S. Tomé and Príncipe
Natural ecosystems are comprised of forests, rivers, water streams and marine environments. They present a rich diversity of species and several complex ecological factors such as variations in moisture and luminosity. The abiotic environment is multistratified, containing species that compete among themselves and adapt to different conditions. These ecosystems can be found in important protected áreas: Obô nature preserve, Tinhosas islands nature preserve, and Rolas island nature preserve (source: Rapac - rede das Áreas Protegidas de África Central – Central African Network of Protected Areas).
These protected areas are home to species that are important both at the national and international levels.
There are also the following altitude forests: Low altitude forest (0-800m), mountain forest (800-1400m) and mist forest (1400-2024m).
2.6 Forest ecosystem
The first and most thorough studies on Santomean vegetation were carried out in 1932 and 1933 by Exell. They were published in 1944 and 1956.
According to Exell, except for a few very small mangroves and sand dunes on the coast, São Tomé’s original vegetation was composed of humid forests that covered the island uniformly, from the coast to the summit of the Pico de São Tomé. Exell defined three separate forest regions in São Tomé, indicated below.