Herpetofauna of the eastern African forests - Biogeography and Ecology of the Rain Forests of Eastern Africa - page 176

main areas of orest in easten Africa were frag-
mented even more. Today, the most extensive and
most important of these forests are to be found
along the Easten Arc mountains of Tanzania (see
Lovett (Chapter 4, this volume) for a detailed
descripion of the Easten Arc mountains and for-
ests). Less humid forests have also persisted
elsewhere, such as coastal forest.
In a study of the birds of Africa, Moreau (1966)
referred to a 'Tanganyika-Nyasa' forest fauna,
running from the forests of the T aita Hills in
Kenya south to parts of Malawi and northern
Mozambique, and I have used his concept to help
deine the limits of the easten forests in Africa.
Those forests found on the crystalline block
mountains of easten Africa include the Taita
Hills, North and South Pare, East and West
Usambara, Nguru, Uluguru, Malundwe, Rubeho,
Uzungwa and the Mahenge mountains. Barbour
& Loveridge (1928) collected extensively in the
Usambara and Uluguru forests but other forested
areas on crystalline block mountains have
received little attenion. Biologists have only
recently begun to investigate the large forested
areas of the Uzungwa scarp.
Earlier collecing by Loveridge (1933) in the
Uzungwas was mainly in the plateau forests rather
than those of the scarp. He also collected in a
large area of southwest Tanzania known as the
Southen Highlands. Loveridge used general
terms indicaing tribal areas to describe the
various secions in which he collected, such as
Ubena and Ukinga, and botanists have also used
these. While no longer in general use, their mean-
ing is widely understood both within and outside
Tanzania, and they are retained here for con-
sistency. The geography, geoloy and terminology
of the Southern Highlands area are discussed in
detail by Cribb & Leedal (1982).
Forests to the south in Malawi menioned
include the Misuku Hills, the Nyika Plateau,
Nchisi Mountain, Mount Mulanje and Mount
Thyolo. The vegetaional details of these are dis-
cussed by Chapman & White (1970).
Evidence rom bird distribuions (see Moreau,
1966) in northen Mozambique as well as the
presence of a species of forest microhylid frog in

The forests included in this study: past
and present

Any understanding of the forest-dependent fauna
present today depends on a knowledge of the geo-
logical, climatological and vegetational changes
which have taken place over millions of years on
the African coninent. Although details of such
changes, especially during and after the Pleisto-
cene, and the human effects on vegetaion remain
matters of controversy (see Chapters 4 and 5) the
general effects of such changes may be broadly
described as follows. It is clear that perhaps dur-
ing several periods the coninent was much more
extensively forested than at present. Forest
epanded and contracted over ime, depending on
both geological and climatological vicissitudes; at
present, its cover is only a small porion of what it
has been at other periods in the past (see Chapter
3). Such expansions and contracions of forest
had profound effects on both forest and non-for-
est organisms. Forests, especially moist tropical
forests, are complex ecosystems; it appears that
once organisms have specialised and evolved to
live within such a complex system, very few are
able to eist far outside its bounds. As Kingdon
(1971) has pointed out ' ...forest animals ...are
generally fairly rigidly ied to their habitat.' Thus
when the distribuion of moist forest finally con-
tracted, only some species were able to respond by
adaping to a non-forest habitat, such as the drier,
more open woodland which characterises much of
easten and southen Africa today. Depending to
some extent on the ime over which the moister
forest was reduced, many forest-dependent spe-
cies would probably have become extinct as the
habitat on which they depended gradually
receded. Those which survived probably did so
because they were able to adapt to life at the forest
edge, or in thicket or other types of degraded
forest, or because the area of forest on which they
depended remained relaively intact. Such areas
have been termed forest 'refugia' (Hamilton,
1976; Diamond & Hamilton, 1980). Once the
forests which linked West and East Africa were
separated for the final ime, perhaps about 20
million years BP J. Lovett, unpublished data), the