Location and General Description
The Southern Zanzibar-Inhambane Coastal Forest Mosaic runs approximately 2200 km along the eastern coast of Africa, from just north of the town of Lindi in southern Tanzania to just south of Xai-Xai in Mozambique. There are also isolated outliers of habitats closely similar to those along the coast in the foothills of mountains in western Mozambique, Malawi and Zimbabwe, although these are small and the habitat has been extensively altered. The ecoregion is predominantly comprised of coastal forest mosaic within 50 km of the Indian Ocean, although it extents up to c.200 km inland in the above mentioned outliers. It is also found on small offshore islands in Mozambique, including the Bazarruto Archipelago.
Topographically, this ecoregion is a rolling landscape, with isolated higher plateaus and inselbergs, especially in the northern part of the ecoregion. To the south, sand dunes are an important feature, as they support coastal forest and thicket vegetation types. Inland from Lindi, remnant areas of Miocene uplift have been eroded into plateau areas that rise up to 800 m in altitude. Further south the Macondes Plateau in southern Tanzania and northernmost Mozambique upland areas rise up to 1000 m altitude. The outliers in Malawi and Zimbabwe are associated with larger mountain areas (e.g. Mt. Mulanje and the Chimanimani area) (Chapman and White 1970, Dowsett-Lemaire 1990, Burgess and Clarke 2000).
The ecoregion is tropical in the northern portion and borders sub-tropical in the southern portion. In the Lindi area there is one prolonged dry season and one wet season, although showers are frequent. Rainfall, controlled by monsoon winds, is around 800-1000 mm per year, although it is higher on some of the plateaus. In coastal Mozambique the climate follows the same general trends, but with lower rainfall in the north (around 800 mm per annum). Mean maximum temperatures are 30-27° C in the north and 24° C in the south of the ecoregion. Mean minimum temperatures are 18-15° C throughout the ecoregion. Towards Beira in southern Mozambique there is a significant difference between the day length in winter and summer, which is not the case in the northern part of the ecoregion.
Geologically the portion of the ecoregion found in Tanzania is mainly comprised of Tertiary marine sediments that have been uplifted and then eroded. In northern Mozambique there are many inselbergs protruding from these sediments, with the former comprised of Archean (over 2500 mya) sediments that have been deformed and eroded over hundreds of millions of years. Adjacent to the coast there are recent dunes, and around river mouths, river-borne deposits are found (Buckle 1978). The soils developed over these sediments are also complex with six FAO soil units found in the ecoregion.
The human population of the ecoregion is higher than inland regions, but is not very high in any particular area. Moreover, there are no large towns in the ecoregion. Population densities of 20-50 persons per km2 are recorded along most of the Mozambique coast, although the prolonged war in Mozambique means that older statistics are likely to be unreliable. The population density on the Macondes Plateau in southern Tanzania and northern Mozambique is higher than the rest of the ecoregion, and is associated with the areas of higher land and better climate for farming.
In terms of the phytogeographical classification of Moll and White (1978) and White (1983), this ecoregion falls within the Zanzibar-Inhambane regional mosaic, and reaches the northern limits of the Tongaland-Pondoland regional transition zone. A recent reclassification of the phytogeographical framework of the region (Clarke 1998) has defined the northern part of the area to fall within the Swahili Regional Center of Endemism, based on the large number of plants confined to it. This new phytochorion is mapped to extend to northern Mozambique, somewhat further south than the border we are using here. The majority of the Southern Zanzibar-Inhambane Coastal Forest Mosaic ecoregion is found in the new Swahili-Maputaland regional transition zone of Clarke (1998). The vegetation consists of a mosaic of savanna woodland, forest patches, thickets, swamps and littoral vegetation types. At the coastline the littoral vegetation transitions into mangrove vegetation, especially in sheltered bays and by rivers.
This ecoregion is typified by a high density of endemic species in the northern portion (southern Tanzania) followed by an almost complete lack of data in the central portion (northern and central Mozambique). The southern portion (in Mozambique) is again characterized by narrowly endemic species (Stuart et al. 1990; Burgess et al. 1998; Stattersfield et al. 1998; Burgess and Clarke 2000). Outliers of the vegetation type, with some of the characteristic species and other narrow endemics are found in Malawi and Zimbabwe (Burgess and Clarke 2000). Species richness is low for the strict forest species, but boosted by the many savanna woodland and wetland species that inhabit the extensive areas of non-forest habitat in the ecoregion.
Within the plants and vertebrates there is a significant center of endemism in the Lindi area, associated with the different plateaus (especially Rondo) in the area (WWF and IUCN 1994; Burgess et al. 1998). The Rondo plateau area has one of the most important concentrations of endemic plants in eastern Africa (more than 100 species in less than 50 km2 of forest). Further to the south there is another known area of endemism, on the islands associated with the Bazarruto Archipelago (e.g. Broadley 1990, 1992). Other endemics are scattered through the forest habitat, especially in lowland Malawi and Zimbabwe.
The general lack of data for the middle part of this ecoregion prevents an accurate assessment of the overall biological importance of the ecoregion. There are large numbers of endemic species in the northern and southern part of the ecoregion, but the lack of biological study in the central portion means, due to the civil war in Mozambique, means that few endemic species are recognized, although they are expected to be present. Burgess et al. (1998) showed how the number of endemics declines southwards along the coastline. He also showed how the area around Lindi was of exceptional importance, whereas northern Mozambique had low known importance. Recent expeditions to northern Mozambique have discovered new species of reptile and plants (Branch, in lit.), hence it seems that the earlier predictions are likely to be confirmed.
Current information concerning avifaunal distribution, diversity, and endemism in this ecoregion is sparse, especially in northern and central Mozambique. The only strict endemic bird in this ecoregion is Reichenow’s batis (Batis reichenowi), which some taxonomists do not recognize as a valid species. The near-endemic species, which include the east coast akalat (Sheppardia gunningi, VU) and the Spotted ground thrush (Zoothera guttata, EN), are also found elsewhere along the eastern coast of Africa, and sometimes further inland. Further investigation in this region, in particular in northern Mozambique, will likely add to the list of bird species and may discover additional interesting species. Some bird sub-species are also endemic to this ecoregion (Burgess and Clarke 2000).
The mammals in this ecoregion are also less known than in surrounding areas, again particularly in northern Mozambique. Many of the larger mammal species are shared with the neighboring Eastern Miombo Woodlands, including elephant (Loxodonta africana), buffalo (Syncerus caffer), sable antelope (Hippotragus niger), roan antelope (H. equinus), and Lichtenstein’s hartebeest (Alcelaphus buselaphus lichtensteini). The only endemic mammal present is Vincent’s bush squirrel (Paraxerus vincenti) which is confined to Mt. Namuli in Mozambique. As with other groups, further research is needed to better determine the current mammalian faunal content of this region. One of the other effects of the Mozambique war has been a reduction of the population density of larger mammals due to hunting for food. However there are no details on the extent to which this is occurring in the ecoregion.
Reptiles in this ecoregion contain a number of endemic species, whereas there is only one endemic amphibian, the Mahenge toad (Stephopaedes loveridgei). Among the reptiles, regional and local endemism are high (WWF database). Eighteen species are strictly endemic to the ecoregion. Notable among the reptiles are Ancylocranium and Chirindia (worm lizards), Chameleo and Rhampholeon (chameleons), Scelotes (burrowing skink), and burrowing snakes (Typhlops). Most of these endemics are small ground living or burrowing forms, and given the lack of basic biological research it can be expected that more such species occur and that some of the species believed to be narrowly endemic will be found more widely.
In southern Tanzania the known remaining blocks of forest habitat are small (none more than 20 km2). However, the forests are often set within extensive areas of savanna woodlands and associated habitats. In northern and central Mozambique the status of remaining habitat blocks is mainly known from recent satellite photographs (e.g. Saket 1994). This work indicates that there may be extensive areas of forest/thicket in some places. However, ground-truthing has not been conducted in most areas; thus, these habitats could also be dense fire-maintained savanna woodlands with lower conservation interest. Mozambique Forest Department reports a number of 100 km2 forest reserves that contain coastal forest (Burgess and Clarke 2000). These could be highly significant areas if these size estimates are confirmed. In southern Mozambique there are also a number of forests, but these are typically small.
In this ecoregion the most important forested habitats are in places either unprotected, or very poorly protected. In Tanzania the forests are found in forest reserves. The biologically most important reserve on the Rondo Plateau has been extensively logged, and more than 20 km2 has been replanted by pines and native hardwoods. Logging and planting stopped in the early 1990s due to infrastructure decline. As a result, the forest is regenerating in many areas. In Mozambique prolonged civil war meant that the named forest reserves never received significant protection. The current stability may make attempts to regain these lands under management possible, but there is also a significant risk from opportunist logging companies. There are three protected areas in this ecoregion (Bazaruto, Marromeu, Pomene) are summarized below, but these are found in coastal areas, or in savanna woodland habitats and hence offer little protection to the important forest habitats.
The forests of this ecoregion have probably been reduced in extent over tens of thousands of years (Burgess and Clarke 2000). Currently, around 1000 km2 of forest are known to exist, often in tiny patches. However, the true extent of forest in northern Mozambique is not known.
In southern Tanzania the forest is highly fragmented. Much of this fragmentation is probably natural and related to climate, soils, aspect, etc. However, the influence of man over at least 100,000 years is believed to have further fragmented habitats, especially forests. The high human population density of the Macondes Plateau has resulted in very little remaining forest, although it could be predicted from the climate that the natural vegetation of other higher altitude areas in the region, that the area would be a form of closed-canopy forest. Some habitat has been lost due to commercial exploitation. For example, the natural Milicia excelsa forest of the Rondo Plateau was heavily logged by British contractors in the 1950s, with over 20 km2 of plantations established on the site of the natural forest. In some places natural forest is now regenerating within these plantations.
Further south in Mozambique the situation is much less known. Some areas probably never supported much forest, as the area is in the rainshadow of Madagascar and has 800 mm rainfall, as opposed to around 1000 mm north and south of this region. Expeditions to this area from the 1600s found few people in the inland areas (Burgess and Clarke 2000), and thus the population’s direct effect on the vegetation is likely to have been quite small. However, they may have increased the incidence of fires, and thus indirectly affected the vegetation. During the prolonged civil war in Mozambique, which only ended in the 1990s, general instability may have allowed forest-thicket to regenerate in many areas as farming activities were curtailed and people moved to safer areas. However, as many of the people moved closer to the coast, resource-use pressures may have become intense in some areas.
Types and Severity of Threats
Threats to this ecoregion vary from commercial logging in the newly accessible forests of Mozambique and pitsawing of valuable timber in Tanzania, to forest clearing for agriculture. In many cases the severity of these threats is poorly known, as the areas are remote and there is little available information on the sites. In southern Tanzania the main threats come from the decay of the Forestry Division to the point where they have little effective presence on the ground in some areas. Some recent project support has assisted to improve this situation, but funding is not stable and generally does not last for long-enough to make a significant difference on the ground.
Justification of Ecoregion Delineation
The Southern Zanzibar-Inhambane Coastal Forest Mosaic lies between the Lukuledi River in southern Tanzania and the Changane River in southern Mozambique. These boundaries are similar to the modifications to the Zanzibar-Inhambane Regional Mosaic proposed by Clarke (1998), which was divided into a northern Swahilian Regional Center of Endemism and a southern Swahilian-Maputaland Regional Transition Zone. The southern boundaries follow those of White (1983). The northern boundary was shifted north from Clarke’s (1998) boundary to the vicinity of the Lukuledi River in southern Tanzania, as this area represents a possible transition among biotas (WWF 1998). Further investigation of this pattern is needed to better understand the biogeographic relationships.
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Prepared by: Jan Schipper and Neil Burgess
Reviewed by: In progress