Coastal dry forests in northern Mozambique

Abstract

Background and aims - The Coastal Forests of Eastern Africa, stretching along the Indian Ocean coastline from Somalia to Mozambique, are considered by Conservation International to be a global biodiversity hotspot - an area of high diversity and endemism under increasing threat. Although the largest remaining extent of these forests is reported to be found in Mozambique, very little is known on their extent, condition and composition here. In addition, the term 'coastal forest' has been used in different ways by different authors. This paper defines and characterises coastal dry forests found in northern Mozambique and assesses their present extent, botanical composition, conservation importance and the threats to these forests. Methods - The study area of 18,150 km2 lies in Cabo Delgado Province in north-east Mozambique, adjacent to Tanzania. Its limits are determined primarily by geological substrate and landform. Four smaller study sites were chosen covering a range of landforms. Manual interpretation of satellite imagery dating from 1999-2002 was used to calculate possible previous and present extent of 'dense vegetation'. Extensive field collecting was used in determining botanical composition and distribution patterns. IUCN Red List assessments were carried out on selected species using distributional criteria. Results - Dry forests similar to those in southern Tanzania are found widely scattered across coastal Cabo Delgado, sitting in a matrix of miombo woodland and other vegetation types. However, forest cover is not as extensive was believed. We calculate that the original extent of 'dense vegetation cover', which includes coastal dry forest, was 6087 km2. Owing to clearance over the last 150 years this is now only 1182 km2, of which perhaps only 400 km2 is moderately-intact dry forest. In this southern part of their range such forests are essentially dry, not moist and mesic, and dominated by a high proportion of deciduous or sclerophyllous evergreen trees. The plant species composition differs significantly from that of the surrounding woodlands. There is a marked change in species composition between forest patches along the coast, and they contain numerous species with restricted global distribution. Since 2003, 68 species new to Mozambique have been recorded from Cabo Delgado in addition to 36 possible new species. Many new records are of species previously only known from south-eastern Tanzania. Previously recorded patterns of restricted distribution and high species turnover between forest patches in Kenya and Tanzania are confirmed. Seven coastal forest species were assessed as Endangered. Regional context and conservation - Coastal dry forests are discussed in relation to the more widespread 'sand forests' of the continental interior of south-central Africa, and shown to have similarities in ecology, species composition, soils and ecology. Very little of the present extent of coastal forests in Mozambique lies within protected areas. The threats to their continued existence in the face of exploitation for timber, agriculture and oil exploration are outlined.