Ch. 3— Status of Biological Diversity • 81 



Table 3-6.— Oceanic Islands" 

 With More Than 50 Endemic Plant Species 



Percentage 

 Island Endemics endemism 



Madagascar =9,000 



Cuba 2,700 46 



New Caledonia 2,474 76 



Hispaniola" 1,800 36 



New Zealand 1,618 81 



Sri Lanka =900 



Taiwan = 900"= 



Hawaii 883 91 



Jamaica 735 23 



Figi =700 



Canary Islands 383 



Puerto Rico 332 12 



Caroline Islands 293'= 



Trinidad and Tobago 215 



Galapagos 1 75 25 



Mauritius 172 



Ogasawara-Gunto ISI*^ 



Reunion =150 



Vanuatu =150 



Tubuai <140 



Comoro Islands 136 



Socotra 132 



Bahamas 121 



Sao Tome 108 



Marquesas Islands 103 



Samoa alOO 



Juan Fernandez 95 



Cape Verde 92 



Madeira 86 



Mariana Islands 81'= 



Lord How Island 73 



Seychelles 73 



^Excludes Australia, New Zealand, Borneo, New Guinea, and Aldabra, 

 '^Hispaniola comprises the nations of Haiti and ttie Dominican RepubliC- 

 ^Omits monocoyledons 



SOURCE: Adapted from A.H Gentry, "Endemism in Tropical Versus Temperate 

 Plant Communities," Conservation Biology, M. Soule(ed.) (Sunderland, 

 MA: Sinauer Associates, Inc., 1986); and H, Synge, "Status and Trends 

 of Wild Plants," OTA commissioned paper, 1985, 



States, since passage of the National Environ- 

 mental Policy Act. 



Yet pollution remains a major threat to bio- 

 logical diversity, because abatement is often ex- 

 pensive and is sometimes a very complex or- 

 ganizational task, especially virhen it depends 

 on international cooperation. Acid rain is an 

 example. In Scandinavia, several fish species 

 have declined in numbers because of acidifi- 

 cation of lakes; in eastern Canada, a trout spe- 

 cies has been placed in the severely threatened 

 category (37). International pollution by acid 

 rain has recently been reported to extend far 

 from industrial regions into Zambia, Malaysia, 

 and Venezuela, for example. 



Climate change is apparently being caused 

 by increased carbon dioxide and atmospheric 

 dust, which result from fossil-fuel burning and 

 from the release of carbon stored in vegetation 

 when extensive areas are converted from for- 

 est to cropland or sparsely vegetated grassland. 

 The expected consequences include significant 

 changes in temperature and rainfall patterns. 

 Temperature rises seem likely to occur rapidly, 

 at least in evolutionary terms, so diversity will 

 probably incur a net loss during the next cen- 

 tury (38). 



In both industrial and developing countries, 

 diversity is lost as land is converted from for- 

 est, grasslands, and savanna to cropland or pas- 

 ture. If the land being converted will support 

 permanent agriculture with relatively high 

 yields, the effect on diversity is contained. Mod- 

 erate areas of such land can support substan- 

 tial populations. But much of the newly cleared 

 land is marginal or totally unsuitable for the 

 cultivation or grazing practices being applied. 

 As a result, extensive areas must be cleared, 

 especially where the land is so poor that it de- 

 grades to wasteland and is abandoned after a 

 few years, which is typical in the moist tropi- 

 cal forest regions and in semiarid areas of both 

 the temperate and tropical zones (30). 



The underlying causes of inappropriate land 

 clearing are many and exceedingly complex. 

 Population growth, poverty, inappropriate agri- 

 cultural technologies, and lack of alternative 

 employment opportunities are all problems far 

 too complex for biologists and conservationists 

 alone to resolve. 



Population growth in itself may not seem in- 

 trinsically threatening to biological diversity. 

 In some industrial countries, such as the United 

 States and Japan, disruption of ecosystems has 

 been mitigated by urbanization, establishment 

 of parks, and land use regulation (30). But the 

 connections between affluent populations and 

 their impacts on biological diversity are ob- 

 scured by the complexity of commerce. The Jap- 

 anese, for example, carefully protect the diver- 

 sity of their own remaining forests, but they 

 use large quantities of timber from forests in 

 other countries where controls are lax. Much 

 has been written about the "hamburger con- 



