Читать книгу Ecology - Michael Begon - Страница 23

Conservationists have to make hard decisions in their quest to preserve biological diversity. Given limited resources, how can the most species be supported at minimum cost? One way is to focus attention on 'biodiversity hot spots' of species that are found nowhere else. Myers et al. (2000) took this approach when mapping the entire globe in terms of exceptional concentrations of endemic species coupled with exceptional loss of habitat (and therefore subject to a greater degree of threat to biodiversity than areas without such habitat loss). Hot‐spot boundaries were set according to the characteristic biotas they contain: examples include island groups such as the Galápagos (Section 1.3.2) and Hawaii (Section 1.4.2), and 'ecological' islands such as the East African Great Lakes (Section 1.3.3) or clearly defined continental units such as the Cape Floristic Province in South Africa. The taxa included in the analysis consisted of vascular plants, mammals, birds, reptiles and amphibians. Figure 1.13 shows 25 identified hot spots that between them contain 133 149 plant species (that is, 44% of the world's plants) and 9645 vertebrate species (35% of the world's total). Or to put it in another way that emphasises their importance, we can say that this set of hot spots provide the sole remaining habitats of 44% of the world's plant species (and 35% of animals).

Figure 1.13 Biodiversity hot spots. Twenty‐five biodiversity hot spots identified because of their exceptional concentrations of endemic species that are undergoing exceptional levels of human induced habitat loss.

Source: From Myers et al. (2000).

The five most prominent hot spots, the tropical Andes, Sundaland, Madagascar, Brazil's Atlantic Forest and the Caribbean, contain 20% of the world's vascular plants and 16% of vertebrate species but together they comprise only 0.4% of the world's surface. Moreover, they are subject to some of the heaviest levels of habitat loss: the Caribbean retains only 11.3% of its primary vegetation, Madagascar 9.9%, Sundaland 7.8% and Brazil's Atlantic Forest 7.5%. There was reasonable congruence between levels of endemism of plants and vertebrates in the hot spots, but note that no invertebrates were included in the analysis. In a geographically more restricted study in South Africa, Bazelet et al. (2016) showed that there was congruence between hot spots of the rather circumscribed diversity of katydids (bush crickets) and the biodiversity hot spots already recognised for much wider groupings, indicating that the conservation of biodiversity hot spots may often also protect non‐target organisms.

Myers et al. (2000) called for a more than 10‐fold increase in annual funding from governmental and international agencies to safeguard these hot spots.