Neil Burgess

The distribution of cultural and biological diversity in Africa

Anthropologists, biologists and linguists have all noted an apparent coincidence in species diversity and human cultural or linguistic diversity. We present, to our knowledge, one of the first quantitative descriptions of this coincidence and show that, for 2° × 2° grid cells across sub–Saharan Africa, cultural diversity and vertebrate species diversity exhibit marked similarities in their overall distribution. In addition, we show that 71% of the observed variation in species richness and 36% in language richness can be explained on the basis of environmental factors, suggesting that similar factors, especially those associated with rainfall and productivity, affect the distributions of both species and languages. Nevertheless, the form of the relationships between species richness and language richness and environmental factors differs, and it is unlikely that comparable mechanisms underpin the similar patterns of species and language richness. Moreover, the fact that the environmental factors considered here explain less than half of the variation in language richness indicates that other factors, many of which are likely to be historical or social, also influence the distribution of languages.

The Uluguru Mountains of eastern Tanzania: the effect of forest loss on biodiversity

The Uluguru Mountains in eastern Tanzania contain at least 16 endemic vertebrate and 135 endemic plant taxa, with hundreds of more taxa shared only with forests in eastern Tanzania and Kenya. This degree of endemism is exceptional in tropical Africa, and the Uluguru Mountains are one of the 10 most important tropical forest sites for conservation on the continent. Surveys carried out during 1999–2001 updated information on the status of forests and biodiversity across the Uluguru Mountains. Forest area has declined from c . 300 km 2 in 1955 to 230 km 2 in 2001. Forest loss has been greatest over altitudes of 600–1,600 m, and concentrated in submontane forest. During the recent surveys most of the endemic and near-endemic vertebrate species known from the Uluguru Mountains were re-recorded, but three endemic snake species and two near-endemic bird species were not found. These species were previously known from the elevations where deforestation has been greatest. More than 50 plant species are also known only from the altitude range that has been heavily deforested. The primary cause of forest loss has been clearance for new farmland. The forest that does remain is largely confined to Catchment Forest Reserves managed for water by the Tanzanian Government. Without these reserves the loss of forest, and hence the loss of biodiversity, in the Uluguru Mountains would most likely have been much greater.

Major gaps in the distribution of protected areas for threatened and narrow range Afrotropical plants

We investigated the major patterns of plant rarity in sub-Saharan Africa, and looked for the most significant gaps in the reserve network of the region in terms of representing the distribution of threatened and geographically rare plants. Comparisons of the species ranges captured by the network of reserves were made against the proportion of species captured by randomly generated sets of areas and against a theoretical near minimum set of areas that represent all species once. At this scale of analysis, the network of large IUCN-coded reserves (the official ‘protected areas’) performs poorly against random and systematic selection procedures. Significant gaps in the IUCN-coded protected areas are in coastal Gabon/Cameroon, in the various tropical montane forest areas (Cameroon Highlands, Eastern Arc Mountains, Ethiopian Mountains), in lowland coastal eastern Africa, and in the South African Cape. Some of these gaps, for example in the Eastern Arc and eastern African coastal regions, are covered on the ground by a network of Forest Reserves under the management of national Forestry Authorities. The networks of Forest Reserves in Ghana, Nigeria, Cameroon, Uganda, Kenya, Zimbabwe, Zambia and Sierra Leone also fill reservation gaps for rare African plants in these countries. Upgrading the conservation status of some key Forest Reserves, which has been gradually happening for some decades, is proposed as an efficient way to enhance the protected area network of the Afrotropical region for the conservation of rare African plant species.

Integrating biodiversity priorities with conflicting socio-economic values in the Guinean–Congolian forest region

Identifying important areas for conserving biodiversity has attracted much discussion, but relatively few studies have dealt with conflicting socio-economic interests in a manner that is fully accountable. For the Guinean–Congolian forest region, we applied quantitative methods to select a network of coarse-scale areas sufficient to represent all forest mammal and bird species at least once. In a separate exercise, we prioritised 50% of the region to represent the same species as many times as possible. In both cases, we sought to minimise potential conflicts between conservation and other socio-economic imperatives by considering benefit-to-cost ratios. We found that by choosing areas to reduce conflicts, we were able to increase markedly the proportion of selected areas with low or medium conflict and decrease the proportion with high conflict. Nonetheless, we cannot expect that conservation goals will always be met unless some of these conflicts are faced and resolved. By working together with specialists from both the biological and socio-economic fields, we show that easily implemented quantitative tools could be useful for supporting the process of finding important areas for biodiversity conservation, while avoiding much of the conflict with other interests.

How much of the vertebrate diversity of sub-Saharan Africa is catered for by recent conservation proposals?

A database documenting the distribution of birds, mammals, amphibians and snakes across 1° latitude and longitude squares of mainland sub-Saharan Africa provides an opportunity to quantify how many of these vertebrates are potentially catered for by recent large-scale conservation proposals. Sets of priority areas proposed by BirdLife International, the World Wildlife Fund (USA), the World Conservation Union and the World Wide Fund for Nature, Conservation International, and the World Resources Institute contain between 45 and 93% of 3752 species of birds, mammals, snakes and amphibians breeding in this area. Gaps in the coverage of vertebrates were found in all large-scale proposals, and these are mapped. Most of the conservation proposals perform better than random selection of similar sized areas of Africa, with the proposals focused on species performing more efficiently than schemes based on large areas of intact habitat or process-related criteria. Four of the schemes approach the performance of a complementarity-based algorithm that aims to maximise the number of species captured within a given area of land, and which has been widely advocated as a tool for conservation planning. The reasons for this are discussed and the relevance of the results for conservation planning at coarse and fine scales are explained.

Patterns of species richness and narrow endemism of terrestrial bird species in the Afrotropical Region

Geographical patterns and peaks of species richness and narrow endemism (defined by range-restrictedness and range-size rarity) are described for terrestrial Afrotropical birds and subsets thereof based on residency, endemism, and taxonomy. Species richness for residents and Afrotropical endemics (species globally restricted to sub-Saharan Africa) peaks along the mountains and adjacent lowlands of eastern and southern Africa. Isolated mountains in central and western Africa and the lowlands of the north-eastern Congo Basin (Ituri) are highlighted to a lesser degree. Peaks of narrow endemism occur in these areas as well as in the Ethiopian Highlands (particularly for non-passerines), Somalia (particularly for passerines), and the Angolan Escarpment. Within residents, patterns of species richness vary greatly between Afrotropical endemics (which concentrate in forests on mountains and adjacent lowlands, and the southern Brachystegia woodlands) and non-endemic residents (which concentrate in Sudanian woodlands and the Ethiopian Highlands). Patterns of species richness of residents (species that breed in the Afrotropics) and non-breeding migrants (non-breeding visitors to the Afrotropics) also show notable differences. The latter concentrate in areas close to the Palaearctic, which forms their distributional range centres. Patterns of species richness and narrow endemism for Afrotropical endemics show broad-scale coincidence within mountains or mountain–lowland complexes, particularly the Cameroon–Bamenda Highland system, East African rift system and Eastern Arc mountains. However, fine-scale coincidence of peaks of species richness and narrow endemism within these complexes is low. Narrow endemism peaks occur in areas of topographical complexity, which may have conferred localized climatic stability over short-, medium-, and long-term climatic cycles (sensu Fjeldsa, 1994; Fjeldsaet al., 1997), allowing these areas to act as ‘species pumps’. Species accumulate in areas of high productivity. Lack of fine-scale coincidence of narrow endemism and species richness peaks have implications for conservation prioritization exercises.