Chapter 1 



Summary and Options for Congress 



Most biological diversity survives without hu- 

 man interventions to maintain it. But as natural 

 areas become progressively modified by human 

 activities, maintaining a diversity of ecosytems, 

 species, and genes will increasingly depend on 



intervention by applying specific technologies. 

 A spectrum of technologies are available to sup- 

 port maintenance of biological diversity (de- 

 fined in box 1-A). 



Box 1-A.— What Is Biological Diversity? 



Biological diversity refers to the variety and variability among living organisms and the ecological 

 complexes in which they occur. Diversity can be defined as the number of different items and their 

 relative frequency. For biological diversity, these items are organized at many levels, ranging from 

 complete ecosystems to the chemical structures that are the molecular basis of heredity. Thus, the 

 term encompasses different ecosystems, species, genes, and their relative abundance. 



How does diversity vary within ecosystem, species, and genetic levels? For example, 



• Ecosystem diversity: A landscape interspersed with croplands, grasslands, and woodlands has 

 more diversity than a landscape with most of the woodlands converted to grasslands and 

 croplands. 



• Species diversity: A rangeland with 100 species of annual and perennial grasses and shrubs 

 has more diversity than the same rangeland after heavy grazing has eliminated or greatly re- 

 duced the frequency of the perennial grass species. 



• Genetic diversity: Economically useful crops are developed from wild plants by selecting valu- 

 able inheritable characteristics. Thus, many wild ancestor plants contain genes not found in 

 today's crop plants. An environment that includes both the domestic varieties of a crop (such 

 as corn) and the crop's wild ancestors has more diversity than an environment with wild ances- 

 tors eliminated to make way for domestic crops. 



Concerns over the loss of biological diversity to date 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 many of the interests concerned and may misdirect how concerns should be ad- 

 dressed. 



THE PROBLEM 



The Earth's biological diversity is being re- 

 duced at a rate that is likely to increase over 

 the next several decades. This loss of diversity 

 — measured at the ecosystem, species, and ge- 

 netic levels — is occurring in most regions of the 

 world, although it is most pronounced in par- 

 ticular areas, most notably in the tropics. The 

 principal cause is the increasing conversion of 

 natural ecosystems to human-modified land- 



scapes. Such alterations can provide consid- 

 erable benefits when the land's capability to sus- 

 tain development is preserved, but compelling 

 evidence indicates that rapid and unintended 

 reductions in biological diversity are under- 

 mining society's capability to respond to future 

 opportunities and needs. Most scientists and 

 conservationists working in this area believe 

 that the problem has reached crisis proportions, 



