Department of Zoology
Hotspot Guinean Forests
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
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
Earth’s Biologically Richest and Most Endangered Terrestrial
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
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
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.
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).
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
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.
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
has most likely recently gone extinct. Figures for bird diversity and
endemism may not be particularly high (514 species and 90 (18%)
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
the white-necked rockfowl (Picathartes
or the Nimba flycatcher (Malaenornis
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
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
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.
Plants Mammals Birds Reptiles Amphibians Freshwater Fishes
9000 320 785 210 221 512
1800 67 75 52 85 143
20 20.9 9.6 24.8 38.5 27.9
Staatliches Museum für Naturkunde Stuttgart
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