Eastern Africa Coastal Forest Programme: Regional Workshop ...

Swahili regional centre of endemism and the Swahili/Maputaland regional transition
zone:
Eastern Limit: Eastern African seaboard, including the off-shore islands of Pemba,
Zanzibar and Mafia and all islands up to 100 km east of the continental African coast
between 2 o - 25 o S but may also include Inhaca Island at 26 o S. Mangrove forests are
not included as eastern African Coastal Forests, since they are treated as an azonal
vegetation unit outside of the Zanzibar-Inhambane [i.e. Swahili] region (White,
1983).
Northern Limit: Somalia, where the northernmost Coastal Forest variant formation
types and transitional formation sub-types are the scrub forest and a riverine forest
between Bad Daada and Raas Kaamboni. The coastal extent of the Coastal forest area
occurs further south at the Kenya-Somali border, where the Mundane Range of hills
meets the sea.
An outlying island of Eastern African Coastal Riverine Forest occurs further north
along the Jubba River at Bu'ale, 1 o 10'N, 2 o 35'E.
North-western Limit: Kenya, boundary of Zanzibar-Inhambane regional mosaic as
indicated by White (1983). An outlying island of eastern African Coastal Riverine
Forest occurs further to the northwest along the Tana River.
Western Limit: Tanzania, eastern basement edge of the Eastern Arc Mountains south
to lowland Udzungwas at Matundu Forest Reserve, within the Kilombero Valley and
at Mahenge. Thence south and then west to Mitucue mountain and Nova Freixo and
then to Machembe and the Malawi Hills in southern Malawi. Distance from the coast
varies but is nowhere more than 450 km.
South-western Limit: Zimbabwe, Haroni and Rusitu forests as indicated by the southwestern
distributional limits of Commiphora zanzibarica, Cassipourea euryoides,
Inhambanella henriquesii and Sterculia appendiculata. The nearby Chirinda forest is
transitional with Afromontane Forest.
Southern Limit: Mozambique, southern edge of Zanzibar-Inhambane regional mosaic
as defined by White (1983). Forest transitional between the neighbouring Tongaland-
Pondoland and the eastern African Coastal Forests extends into northern Natal.
Altitudinal Range: Sea-level to a maximum altitude which varies according to local
ecological conditions, but is nowhere more than 1100 m. The maximum altitude
reached by eastern African Coastal Forest increases away from the coast, and appears
to be greater on small isolated inselbergs compared to larger mountain blocks, e.g.
Coastal Forests extend to 400 m on the Uluguru and Usambara mountains, to 750 m
on the Udzungwa mountains and to 1030 m on Handeni.
Climate: Tropical monsoon climate of the Indian Ocean with a unimodal (south of
Dar es Salaam) to bimodal (north of Dar es Salaam) mean annual rainfall of between
510 and 2000 mm. Eastern African Coastal Riverine Forest may develop in areas with
a lower mean annual rainfall of just 470 mm, since these forests depend on a river for
their water supplies.
Areas beyond the geographical extent outlined above are either to dry (i.e. to the
north, west and southwest), too wet (i.e. upland Afromontane areas) or too cool (to
the south) to support eastern African Coastal Forest.
Eastern Africa Coastal Forests - 53 - Workshop Report, Nairobi February 4-7 2002