From representation to persistence: requirements for a sustainable system of conservation areas in the species‐rich mediterranean‐climate desert of southern Africa
Tóm tắt
Conservation planning has hitherto concentrated largely on the representation of biodiversity patterns within a system of conservation areas. Only recently has there been an emphasis on retaining segments of the optimal conservation area by defining implementation priorities in terms of the irreplaceability of areas and their vulnerability to threatening processes. The conservation of ecological and evolutionary processes that sustain and generate biodiversity, a requirement for a system of conservation areas that promotes biodiversity persistence, has received very little attention. By designing conservation systems in order to represent spatial features as surrogates for ecological and evolutionary processes, and by scheduling the implementation of areas in order to minimise the impacts of threats on these processes, it is theoretically possible to achieve a conservation system that combines retention and persistence. Here we discuss the requirements for establishing a sustainable (retention+persistence) conservation system in southern Africa's Succulent Karoo, a mediterranean‐climate desert that is very rich in plant species. Firstly, we discuss planning issues salient to both representation and design, and indicate the location, size and role in conservation of the spatial components (surrogates for processes) necessary for a system of conservation areas in the Succulent Karoo intended for retention+persistence. Next we lay out the requirements for a conservation system in the region and summarise some existing work on representation and retention of plant species. We then present a protocol for decision‐making and apply it by designing a hypothetical system of conservation areas. Finally, we compare representation of Red Data Book plant species in a system identified for pattern retention with our similar‐sized system designed for retention+persistence. The latter conserves 37% fewer species, indicating that design for persistence incurs a cost in terms of representation. This cost is offset by developing a conservation system that is likely to persist in the face of global change, and that will sustain processes responsible for the maintenance and genesis of biodiversity.
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Tài liệu tham khảo
Bond P., 1984, Plants of the Cape Flora: a descriptive catalogue, J. S. Afr. Bot., 13
Bond W.J., 1990, What can we learn from extinctions and invasions about the effects of climate change?, S. Afr. J. Sci., 86, 429
Cowling R.M., Namaqualand, South Africa—an overview of a unique winter‐rainfall desert ecosystem, Plant Ecol
Cowling R.M., 1989, Biotic diversity in southern Africa. Concepts and conservation, 19
Cowling R.M., The Karoo: ecological patterns and processes
Cowling R.M., 1998, Extraordinarily high regional‐scale plant diversity in southern African arid lands: subcontinental and global comparisons, Diver Distrib, 4, 27
DavisF.W.&StomsD.M.1996Sierran vegetation: a gap analysisSierra Nevada ecosystem project: final report to CongressVolume II. Assessments and scientific basis for management optionsDavis California:University of California Centers for Water and Wildland Resources671‐686.
DeanW.R.J.1995Where birds are rare or fill the air: the protection of the endemic or nomadic avifaunas of the KarooPhD thesis University of Cape Town.
Dean W.R.J., The Karoo: ecological patterns and processes
DesmetP. G.1996Vegetation and restoration potential of the arid coastal belt between Port Nolloth and Alexander Bay Namaqualand South AfricaMSc thesis University of Cape Town.
Desmet P.G., Biodiversity, habitat and range‐size aspects of a flora from a winter rainfall desert in north‐western Namaqualand, South Africa, Plant Ecol
Desmet P.G., The Karoo: ecological patterns and processes
Desmet P.G., 1998, Speciation in the Mesembryanthema, Aloe, 35, 38
Gess F.W., 1981, Some aspects of an ethological study of the aculeate wasps and the bees of a karroid area in the vicinity of Grahamstown, South Africa, Ann. Cape Prov. Mus. (Natural History), 14, 1
Gess S.K., 1989, Flower visiting by masarid wasps in southern Africa (Hymenoptera: Vesperoidea: Masaridae), Ann. Cape Prov. Mus. (Natural History), 18, 95
Gotzman I., Remarkable medium‐term dynamics of leaf succulent Mesembryanthema (Aizoaceae) in the winter‐rainfall desert of northwestern Namaqualand, South Africa, Plant Ecol
Hammer S.A., 1992, The Genus Conophytum
Hartmann H., 1978, Monographie der Gattung Argyroderma N.E.Br. (Mesembryanthemaceae Fenzl), Bot. Jahrb. Syst., 97, 121
Hendricks H., 1998, Traditional stock farming in the Richtersveld, Veld Flora, 84, 86
Hilton‐Taylor C., 1994, Centres of plant diversity. A guide and strategy for their conservation, 204
Hoffman M.T., The Karoo: ecological patterns and processes
Jürgens N., 1991, A new approach to the Namib Region. I: Phytogeographic subdivision, Vegetatio, 97, 21, 10.1007/BF00033899
Jürgens N., 1997, Vegetation of southern Africa, 189
Lombard A.T., 1996, Global change, biodiversity and ecosystem functioning, S. Afr. J. Sci., 92, 115
Lombard A.T., Reserve selection in the Succulent Karoo, South Africa: coping with high compositional turnover, Plant Ecol
Lovegrove B.G., 1986, Coevolution between mole‐rats (Bathyergidae) and a geophyte, Micranthus (Iridaceae), Cimbebasia, 8, 79
Lovegrove B.G., 1989, Spacing and origin(s) of Mima‐like earth mounds in the western Cape Province of South Africa, S. Afr. J. Sci., 85, 108
McNeely J.A., 1994, Protected areas for the 21st century: working to provide benefits to society, Biodiv. Conserv., 3, 390, 10.1007/BF00057797
Milton S.J., 1990, Mima‐like mounds in the southern and western Cape: are the origins so mysterious?, S. Afr. J. Sci., 86, 207
Milton S.J., 1997, Vegetation of southern Africa, 131
Myers N., Hot‐spots of the World
Owen‐Smith N., 1997, Vegetation of southern Africa, 397
Picker M.D., 1996, Pollination by monkey beetles (Coleoptera: Scarabaeidae: Hopliini): flower and colour preferences, Afr. Entomol., 4, 7
Pressey R.L., 1997, National parks and protected areas: selection, delimitation and management, 337
Pressey R.L., 1995, Nature conservation 4—the role of networks, 23
Pressey R.L., Priority conservation areas: a definition for the real world applied to Western New South Wales, Biol. Conserv
Rebelo A.G., 1992, The ecology of fynbos. Nutrients, fire and diversity, 309
Rebelo A.G., 1997, Vegetation of southern Africa, 571
Schmiedel U., Community structure on unusual habitat islands: a comparison of quartz field vegetation in the Knersvlakte and Little Karoo of southern Africa's Succulent Karoo, Plant Ecol
Skead C.J., 1980, Historical mammal incidence in the Cape Province
Todd S.W., The effects of heavy grazing on plant species diversity and community composition in a communally managed semi‐arid shrubland, Namaqualand, South Africa, Plant Ecol
Van Jaarsveld E., 1987, The succulent riches of South Africa and Namibia, Aloe, 24, 45
Vernon C.J., The Karoo: ecological patterns and processes
Von Willert D.J., 1992, Life strategies of succulents in deserts, with special reference to the Namib Desert