S. Tome & Principe - Annobon



ID

587

Author(s)

Ashley Brown and Robin Abell, World Wildlife Fund-US, Washington, DC, USA


Countries

Equatorial Guinea
Sao Tome and Principe

Reviewer(s)

Angus Gascoigne, Environmental Information and Technical Services, São Tomé, São Tomé et Príncipe


Major Habitat Type

Tropical and subtropical coastal rivers

Drainages flowing into

Gulf of Guinea, Atlantic Ocean


Main rivers to other water bodies

Rivers drain from the central highlands of São Tomé and the other islands, radiating towards the coasts. The largest river of São Tomé is the Io Grande, which drains the southeastern portion of the island. Other large rivers on São Tomé include the Abade, the Manuel Jorge and the Rio d\'Ouro and the Rio Papagaio is the longest river on Príncipe (Juste & Fa 1994).



Description

Boundaries

Located off the coast of Equatorial Guinea and Gabon, these volcanic islands include São Tomé (836 km2), Príncipe (128 km2), and Annobón (17 km2), as well as several smaller islands. Most of this ecoregion lies within the Democratic Republic of São Tomé and Príncipe. Annobón is part of Equatorial Guinea and lies 180 km southwest of São Tomé.

Topography

The islands are generally mountainous in the interior, sloping sharply down to the coasts. In São Tomé, one major mountain chain runs north to south while a second runs northwest to southwest. Príncipe has two chains as well, both running east to west (Juste & Fa 1994). The highest peak on São Tomé is 2,024 m asl and on Príncipe it is 948 m asl. On the much smaller island of Annobón the highest peak is 630 m asl (Juste & Fa 1994). 

Freshwater habitats

On each of this ecoregion’s islands, swift rivers marked by waterfalls and rapids descend from highland interiors and flow to the Gulf of Guinea. Most rivers are perennial and experience seasonal fluctuations. The islands of São Tomé and Annobón also have volcanic crater lakes.

Terrestrial habitats

Prior to conversion, the primary vegetation of the ecoregion was tropical rainforest (Juste & Fa 1994). Now much of the land is used for agrarian purposes. The remaining primary and secondary forests fall under the category of lowland forest, montane rainforest, mossy forest, and mangrove forest. The forests on São Tomé, Príncipe and Annobón contain many endemic and imperiled species such as Rinorea thomensis, Afrocarpus mannii, Craterispermum montanum, and Pandanus thomensis (WCMC 2001).

Justification for delineation

São Tomé, Príncipe, Annobón form the boundaries of this ecoregion. These islands were formed by volcanic eruptions that occurred along a fracture in the earth’s crust during the lower Tertiary and early Quaternary (Juste & Fa 1994). Because the islands have never been connected with each other or the mainland, which is about 220 km away from São Tomé and Príncipe and 340 km from Annobón, the flora and fauna are relatively low in richness but high in endemism (Jones 1994). Bioko, the largest island in the Gulf of Guinea, is part of the volcanic chain that includes Mt. Cameroon, São Tomé, Príncipe, and Annobón. However, Bioko is included in the Northern Gulf of Guinea Drainages - Bioko ecoregion [518] because the island was connected to the continent some 10-12,000 years ago and shares a majority of its fish species with those of the mainland (Kamdem Toham, pers. comm., 2000).

Level of taxonomic exploration

Fair. The crater lakes on São Tomé and Annobón are unique habitats that offer unique opportunities for palaeobotanical and palaeoclimatological research. Gascoigne (1993; 1996) provides a bibliography on the fauna of the islands.


References

  • Brown, D. S. (1991). "Freshwater snails of São Tomé, with special reference to Bulinus forskalii (Ehrenberg), host of Schistosoma intercalatum" Hydrobiologia 209 pp. 141-153.
  • Christy, P. (2001). "São Tomé and Príncipe" L. D. C. Fishpool and M. I. Evans (Ed.) Important bird areas in Africa and associated islands: Priority sites for conservation ( pp. 727-731 ) Newbury and Cambridge, UK: Pisces Publications and BirdLife International (Birdlife Conservation Series No. 11).
  • Cumberlidge, Neil (1999). "The freshwater crabs of West Africa: Family Potamonautidae" Paris, France: IRD.
  • FishBase (2001) \Search FishBase\ "<"http://www.fishbase.org/search.cfm ">" (2001)
  • Gascoigne, A. (1993). "A bibliography of the fauna of the islands of São Tomé e Príncipe and the island of Annobon (Gulf of Guinea)" Arquipelago Ciencias Da Natureza 11 pp. 91-105.
  • Holthuis, L. B. (1966). "The R/V Pillsbry deep-sea biological expedition to the Gulf of Guinea, 1964-65. 11. The freshwater shrimps of the island of Annobon, West Africa" Studies in Tropical Oceanography 4 (1) pp. 224-239.
  • Jones, P. J. (1994). "Biodiversity in the Gulf of Guinea: An overview" Biodiversity and Conservation 3 (9) pp. 772-784.
  • Juste, B. J. and Fa, J. E. (1994). "Biodiversity conservation in the Gulf of Guinea Islands: Taking stock and preparing action (Jersey Wildlife Preservation Trust, Jersey, June 4-6, 1993)" Biodiversity and Conservation 3 (9) pp. 759-771.
  • Rossignon, O. (1999) \Contribution à l'ecologie des crevettes dulcaquicoles de São Tomé: du cadre limnologique à l'elevage\ Faculté Universitaire des Sciences Agronomiques de Gembloux.
  • Sayer, J. A., Harcourt, C. S. and Collins, N. M. (1992). The conservation atlas of tropical forests: Africa London, UK: IUCN.
  • Schiøtz, A. (1999). Tree frogs of Africa Frankfurt, Germany: Edition Chimaira.
  • Wcmc (2001) \Vallée de Mai Nature Reserve\ "<"http://www.wcmc.org.uk/protected_areas/data/wh/mai.html ">" (2001)