Ch. 3— Status of Biological Diversity • 79 



Photo credit: U.N. Photo 152.843/K. Muldoon 



Overgrazing in Burl<ina Faso— one major cause of diversity loss. 



bred to give high yields under more artificial 

 conditions. 



The loss of traditional agroecosystems is not 

 restricted to developing countries. Native 

 American farming systems that interplant corn 

 with squash, numerous types of beans, sun- 

 flowers, and many semidomesticated species 

 are reduced to isolated areas now and continue 

 to be abandoned. These systems and crop va- 

 rieties have been described in anthropological 

 literature, but they are lost before being 

 scrutinized by agricultural scientists. 



Agricultural development may cause abrupt 

 disappearance of traditional varieties, as with 

 the replacement of traditional wheat in the Pun- 

 jab region of India, or it may be gradual, as with 

 fruit and vegetable varieties in the United States 

 and livestock breeds in Europe. Locally adapted 

 varieties may become extinct in a single year 

 if germplasm for a traditional variety is lost be- 

 cause of a catastrophe or is destroyed to con- 



trol a disease. Examples include traditional 

 grain varieties that were replaced with mod- 

 ern ones in Africa when seed was eaten dur- 

 ing the recent famine, and local swine popula- 

 tions that were exterminated in Haiti and the 

 Dominican Republic to control a disease and 

 then replaced with modern breeds (15). 



Exploitation of Species 



As noted earHer, concern with loss of biologi- 

 cal diversity historically focused on extinctions 

 or population losses that resulted from exces- 

 sive hunting and gathering. Whales, cheetahs, 

 passenger pigeons, bison, the North Atlantic 

 herring, the dodo, and various orchids are all 

 examples of organisms hunted or gathered in 

 excess (30). 



Today the direct threat to wildlife remains. 

 Numerous monkeys and apes are endangered 

 by overhunting, mainly to supply the demand 



