Chapter 3 



Status of Biological Diversity 



HIGHLIGHTS 



A general consensus exists that biological diversity is being lost or degraded 

 in most regions of the world, but acute threats are largely localized. Despite 

 a weak knowledge base and lack of precise measurements, enough is now known 

 to direct activities to critical areas. 



Concern over the loss of diversity have been defined almost exclusively in terms 

 of species extinction. Although extinction is perhaps the most dramatic aspect 

 of the problem, it is by no means the whole problem. The consequence is a 

 distorted definition of the problem, which fails to account for the various inter- 

 ests concerned and may misdirect how concerns should be addressed. 



The immediate causes of diversity loss usually relate to unsustainable resource 

 development, but the root causes for such development are complex issues 

 of population growth, economic and political organization, and human atti- 

 tudes. The complexity of the causes implies a need for multi-faceted approaches 

 that deal with both the immediate and the root causes of diversity loss. 



INTRODUCTION 



Since life began, extinction has always been 

 a part of evolution. Mass extinctions occurred 

 during a few periods, apparently the results of 

 relatively abrupt geological or climatic changes. 

 But in most periods, the rate of species forma- 

 tion has been greater than the rate of extinc- 

 tions, and biological diversity has gradually in- 

 creased. Recently in evolutionary history, the 

 human species has derived great economic 

 value from ecosystem, species, and genetic 

 diversity and recognized the intrinsic values 

 of diversity. But now that the values are being 

 recognized, there is evidence that the world 

 may be entering another period of massive re- 

 duction in diversity. This time, humans are the 

 cause, and it appears that the consequence will 

 be loss of a substantial share of the Earth's val- 

 uable resources. 



Diversity is abundant at a global level. About 

 1.7 million species of plants and animals have 

 been named, classified, and described (57). (De- 

 scriptions are only superficial for most of these.) 

 The remainder are still unidentified (figure 3-1). 



It is estimated that the world contains 5 to 10 

 million species, and many of these have hun- 

 dreds or even thousands of distinct genetic 

 types. A recent inventory of insect species in 

 the canopy of a tropical forest suggests that 

 many more insect species may exist than pre- 

 viously thought, pushing the estimate for the 

 total of all species to as high as 30 million (14). 



Understanding of biological diversity issues 

 has improved in recent years, in terms of know- 

 ing the extent of diversity and understanding 

 the causes and consequences of changes. Enough 

 information is available in all regions of the 

 world to intervene in the processes that cause 

 diversity loss. 



Drastic reductions in populations of wild ani- 

 mals and plants are not new and have long been 

 recognized as consequences of over-intensive 

 hunting, fishing, and gathering. For example, 

 great bison herds of North America were de- 

 pleted in the 19th century, as were stocks of 

 various whales and bird species (52). The now 

 barren hills of southern China's coasts and is- 



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