80 • Technologies To Maintain Biological Diversity 



Photo credit: D. Etirenfeld 



The green turtle is an example of a species threatened 

 by direct factors, such as exploitation of adults and 

 eggs, and by indirect factors, including nesting beach 

 destruction, ocean pollution, and incidental catch in 

 shrimp trawls. 



from medical research institutions. Some 108 

 primate species are hunted for an international 

 trade worth about $4 million annually (30). For 

 many, perhaps most of these, the capturing 

 process is very destructive. Apes such as the 

 gibbon are captured by shooting mother ani- 

 mals from the treetops and taking any infants 

 that survive the fall. Many of the infants die 

 while passing through the market system. Thus, 

 the 30,000 primates sold in 1982 (30) actually 

 compose a much higher number killed to sup- 

 port the trade. 



The rhinoceros has declined more rapidly 

 over the past 15 years than any other large mam- 

 mal. From 1970 to 1985 there was an almost 

 80-percent decrease in the numbers of rhinos. 



from 71,000 to only about 13,500 today. The 

 most spectacular decline has been that of the 

 black rhino— from 65,000 to 7,000 in the past 

 15 years. Whole populations of black rhino have 

 been almost totally eliminated over the past 10 

 years in Mozambique, Chad, Central African 

 Republic, Sudan, Somalia, Ethiopia, and An- 

 gola. In the past 2 years, Mozambique has lost 

 the white rhinoceros for the second time in this 

 century— a dubious achievement indeed (29). 



The main reason for this catastrophic decline 

 since 1975 is due to the illegal killing of the ani- 

 mal, mostly for its horn. In the early 1980s about 

 one-half of the horn put onto the world market 

 went to North Yemen where it is used for the 

 making of attractive dagger handles, while the 

 remaining half went to eastern Asia where it 

 is used mostly to lower fever, not — as often 

 supposed— as an aphrodisiac (6). 



Plant species are also subject to overharvest. 

 A cycad plant species was reported eliminated 

 in Mexico during just one year when 1,200 spec- 

 imens were exported to the United States (55). 



Vulnerability off Isolated Species 



If the range of species is restricted to a rela- 

 tively small area, such as an island or a moun- 

 taintop forest, a single development project or 

 the introduction of competing or exotic species 

 can lead to loss of diversity. Many recorded ex- 

 tinctions have been animals and plants from 

 oceanic islands (see table 3-6) (52). Some of these 

 areas, such as Haiti, are infamous for deforesta- 

 tion and rapid rates of soil erosion. It may be 

 inferred that diversity loss has been and prob- 

 ably continues to be especially severe on such 

 islands. 



Complex Causes 



Most losses of diversity are unintended con- 

 sequences of human activity, and the species 

 and population affected are usually not even 

 recognized (30). Air and water pollution, for 

 example, can cause diversity loss far from the 

 pollution's source. Substantial gains in reduc- 

 ing these pressures have been achieved in in- 

 dustrial countries, particularly in the United 



