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The Guinean Forest Hotspot  

 

Biodiversity Hotspot Guinean Forests

 

What is a biodiversity hotspot? – The history of the hotspot concept

 

The hotspot concept dates back to as early as 1988 when a seminal paper by British ecologist Norman Myers first identified ten tropical forest “hotspots”. This original categorization was based on exceptional levels of plant endemism and serious levels of habitat loss within the areas under consideration. Only one year later, in 1989, the concept was adopted as institutional blueprint by the U.S. based Non Governmental Organization Conservation International (CI). Until 1990, eight additional hotspots had been added, this time also including non-tropical ecosystems. In 1996, CI decided to reassess the hotspot concept in an effort to examine whether important areas had been overlooked and with the final goal of establishing quantitative measures and thresholds for the designation of biodiversity hotspots. Three years later these measures had been established and were introduced in the form of two basic criteria.

To qualify as a hot spot, a region must meet two criteria: “it must contain at least 1,500 species of vascular plants (> 0.5 percent of the world’s total) as endemics, and it has to have lost at least 70 percent of its original habitat”.

Results of this ’99 assessment were published in the book Hotspots: Earth’s Biologically Richest and Most Endangered Terrestrial Ecoregions (Mittermeier, R. A. et al. 2000)

By 2000, a total of 25 biodiversity hotspots had been identified (comp. Myers et al. 2000)

In a recent reassessment, which pays tribute to the fact that hotspots can change over time (as a result of change in threats and their impacts, i.e. places may become more threatened while others may recover, as well as an improvement of the knowledge of biodiversity, threats, and their impacts), additional hotspots have been identified and previously recognized hotspots have been subdivided. Currently, 34 biodiversity hotspots are being acknowledged (comp. Mittermeier, R. A. et al. 2005), among those are eight areas situated within the African realm, one of which encompassing all of the lowland forests of West Africa. These forests are home to more than a quarter of Africa’s mammals and generally harbour an exceptionally high number of endemic flora and fauna. However, this ecoregion is coming under increasing pressure and is highly threatened by logging, agriculture and increasing human populations (Bakarr et al. 2001a).

 

Online source: Biodiversity Hotspots 

 

Guinean Forests of West Africa – A biological treasure on the cutting edge

 

The Guinean Forest Hotspot – Geography and biological importance

 

The Guinean Forests are part of the vast Guinea-Congolian forests (Guillaumet, 1967). They are commonly split into two main blocks that incorporate several major Pleistocene refugia.

A. The Upper Guinea Forest Ecosystem, extending from Guinea into eastern Sierra Leone, and eastward through Liberia, Côte d'Ivoire and Ghana into western Togo.

B. The Lower Guinea Forest Ecosystem, extending from western Nigeria to the Sanaga River in southwestern Cameroon, including the islands of Bioko and Pagalu, and São Tomé and Príncipe. An area comprising savanna and forest ecotones, known as the Dahomey Gap (stretching from western Togo to eastern Benin), separates the two ecosystems.

Large parts of the Guinean Forest were originally covered by tropical rainforest.  

Fig.1: Guinean Forest Hotspot - Conservation International  

 

The total extend of this area was estimated at 1,265,000 km2, however, it has been dramatically reduced during the last few decades. Today, the formerly closed forest matrix consists merely of a series of forest fragments separated by agricultural communities and degraded lands. Approximately only 141,000 km2 of closed canopy forest are being retained (15% of its original extend). Only a fraction of this area (app. 20,000 km2) has received official and internationally recognized protection status.

The disturbance history is relatively recent in large parts but degradadtion and deforestation rates have continuously accelerated over the past decades. For example, about 80 % of the Upper Guinean forests in Côte d'Ivoire have been destroyed during the last 20 years (Rompay 1993, Parren & DeGraaf 1995, Chatelain et al. 1996).  

 

map editing courtesy of  M. Wegmann, DLR-German Remote Sensing Data Center    

 

 

 

Yet, in terms of original extent, the Guinean Forest hotspot ranks fifth among the 25 originally identified (the top four are the Mediterranean Basin, Indo-Burma, the Brazilian Cerrado and Sundaland). However, the aerea receives a significantly lower ranking when looking at the amount of land area currently under protection (rank 12th).

There is increasing awareness that the relatively small pockets of forest habitat currently conserved in West Africa, and in many other African protected areas (Newmark 1996) may be unable to maintain the long-term viability of the fauna and flora. Conserved areas must therefore expand in size, in the face of increasing socio-economic constraints and conflicting land use options, or become connected by viable corridors that allow the movement of species between the conserved enclaves in order to safeguard the region’s biodiversity (Laurance & Laurance 1999, Gascon et al. 1999, De Lima & Gascon 1999).

 

Species Diversity and Endemism

 

Of the estimated 9,000 species of vascular plants occurring in the Guinean Forest Hotspot, approximately 2,250 (25%) are endemic. Apart from this, throughout the course of analyses of global centres of plant diversity and endemism 14 centres of plant endemism were identified within the Guinean Forest Hotspot: Taï National Park in Côte d'Ivoire, Southeast Forest Remnants in Côte d'Ivoire, Southeast Ghana, Mount Nimba on the Liberia-Guinea-Côte d'Ivoire border, the Cestos-Senkwen River Area in Liberia, Lofa-Mano in Liberia, Sapo National Park in Liberia, the Gola Forests in Sierra Leone, Loma in Sierra Leone, the Cross River National Park in Nigeria, Korup National Park in Cameroon, Mount Cameroon, Príncipe, and São Tomé.

The figures for faunal diversity and endemism in the Guinean Forests are by no means less impressive. With 551 species (almost 50 % of mammals that are native to continental Africa), mammalian species richness, ranks first among the world's 25 hotspots. 45 species (8%) are endemic, among them several highly endangered primate species and subspecies. Five primates are critically endangered and at least on (Procolobus badius waldroni) has most likely recently gone extinct. Figures for bird diversity and endemism may not be particularly high (514 species and 90 (18%) endemics), however,  six Endemic Bird Areas have been recognized by BirdLife International: the Upper Guinean Forests; the Cameroon Mountains; the Cameroon and Gabon Lowlands; the island of São Tomé; the island of Príncipe; and the island Annobón. Some remarkable and charismatic species can be found in these areas, e.g. the white-breasted guinea fowl (Agelastes meleagrides), the white-necked rockfowl (Picathartes gymnocephalus), or the Nimba flycatcher (Malaenornis annamarulae). Fish species richness is quite remarkable in the Guinean Forests hotspot, with more than 510 freshwater fishes (35 % endemic). The 350 species of killifish occurring in the region represent about a quarter of all known species within this group. More than 50% of 60 species of cichlids recorded are endemic to the hotspot. Four of the five endemic genera of cichlids are found only in Lake Barombi Mbo in northwest Cameroon. 

As for terrestrial vertebrates, least is known about reptile and amphibian diversity. Preliminary species richness estimates range between 139 for reptiles and 116 for amphibians, respectively. However these estimates are most likely too low (see below: The herpetological perspective). The number of endemic species within the known herpetological faunas is relatively high, with 46 species of reptile (33%) and 89 species of amphibian (77%) found only within the Guinean Forest Hotspot.

 

Taxonomic Group

Plants
Mammals
Birds
Reptiles
Amphibians
Freshwater Fishes
Species

9000
320
785
210
221
512
Endemics

1800
67
75
52
85
143
Percent endemics

20
20.9
9.6
24.8
38.5
27.9

Contact: 

Dr. Alexander Kupfer

 

Staatliches Museum für Naturkunde Stuttgart

Rosenstein 1

D-70191 Stuttgart

GERMANY

 

Department of Zoology

Herpetology