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of Angola and Mozambique and the Highveld grasslands, lowland fynbos, and succulent karoo of South Africa. All these systems face rapid reduction due to agricultural development or exploitation of timber resources for foreign exchange or fuel wood.
To assess the adequacy of the protected area cover of 15 communities in the exceptionally rich communities of the lowland fynbos (Cape heathlands), Jarman (1986) made use of 1.25 million maps prepared from satellite imagery. More than 69% of this species-rich vegetation formation had already vanished under urban, industrial, and agricultural development, and 21% of the 8,955 square kilometers still in a seminatural state had been invaded by alien woody plants.
A working group of over 40 researchers, administrators, and land owners participated in a 3-year study of the remnant patches of lowland fynbos. The survey identified 153 sites of conservation value and ranked them according to a formula that incorporated quantified attributes such as the rarity of the vegetation type, habitat diversity, total species richness, and the number of threatened plants found on the site. The rating was weighted in terms of the size and shape of the site and its distance from other protected areas and the degree to which the site had been transformed by introduced woody plants or other forms of disturbance. The conservation merit ratings ranged from 13 to 80 out of a possible 100. Only 5 out of 32 sites with a rating above 50 were currently protected, whereas the majority of the other existing reserves had ratings below 30 and were considered either too small, too greatly disturbed, or too low in biotic richness to merit inclusion in a costly protected area network. The study was probably the most detailed of its kind ever undertaken in Africa; indeed, the variety and quality of data available for the analyses are unlikely to become available elsewhere on the continent for many years. The significance of the results lies in the finding that even in an area of considerable financial and manpower resources, past decisions on the selection of sites for protection have been wholly inadequate to meet biological conservation needs.
IDENTIFYING GAPS IN THE NETWORK
The results of surveys of protected area cover based on vegetation maps can only provide the first step in the process of identifying gaps in the network. Much of the diversity of African ecosystems lies in communities that are too restricted or too narrow or patchy in their distribution to be included in the analytical approaches described in the last section of this chapter. Rivers, wetlands, and coastal ecosystems fall in this category. As a consequence of this, they have been largely ignored by African conservation agencies. During the last 10 years, long overdue attention has been devoted to these ecosystems in southern Africa. Some of the experience gained can be described here.
Wetlands in the form of seasonally waterlogged grasslands (dambos) are a characteristic feature of the vast moist savannas of the central African plateau. Drainage of these dambos provides the only rich agricultural soils over vast areas, and much of these systems have been transformed into agricultural lands, dramatically reducing the habitat available to the vulnerable Wattled crane (Grus carunculata)