Ch. 3— Status of Biological Diversity • 71 



Painting by George Sutton/Cornell Laboratory of Ornittiotogy 



The ivory-billed woodpecker is presumed extinct in the 



United States (last verified sighting occurred in 1971) 



and was thought to be extinct worldwide until the 



discovery of at least two specimens in the 



spring of 1986 in eastern Cuba. 



Among tropical countries, Brazil has a list- 

 ing project under way. Lists covering parts of 

 India have been prepared and indicate about 

 900 threatened plant species. The Malayan Na- 

 ture Society is preparing a database on threat- 

 ened plants for the Malaysian peninsula. List- 

 ing projects are also complete or under way in 

 some nontropical developing countries, such 

 as Chile, Pakistan, and Nepal (47). 



Monitoring Indicator Species 

 and Habitats 



Inferring trends in biological diversity from 

 changes in the status of indicator species is a 

 method that relies on time-series data assem- 

 bled for management of economically signifi- 

 cant species or species of special esthetic in- 

 terest. For example, striped bass (known locally 

 as rockfish) has been a highly valued species 

 since precolonial times on the east coast of the 

 United States, and commercial harvest data 

 have been tabulated for areas like the Chesa- 

 peake Bay since 1924. 



For 50 years, the trend in striped bass com- 

 mercial harvest was upward, from around 2 

 million pounds landed in 1924 to 14.7 million 

 pounds in 1973. Then, the trend reversed. By 

 1983, the catch had plummeted by 90 percent 

 to 1.7 million pounds. The decline was believed 

 to be due to a combination of overfishing and 

 chemical contamination of the species' habi- 

 tat (18). Thus, a reduction in populations of 

 other species could be inferred from the striped 

 bass trend. 



Inference from this indicator species was 

 confirmed in 1982 when a 7-year Environmental 

 Protection Agency study indicated the extent 

 of the decline in the bay. Subaquatic vegeta- 

 tion had declined 84 percent since 1971. Areas 

 suffering from lack of dissolved oxygen had in- 

 creased fifteenfold since 1950, and in Baltimore 

 Harbor at least 450 organic compounds, mostly 

 toxins, were identified. Corresponding dramatic 

 declines were documented in native animal spe- 

 cies of the bay, including oysters, shad, and yel- 

 low perch (53). 



The spotted owl is an indicator species for 

 diversity in old-growth forests of the Pacific 

 Northwest. The owl feeds primarily on flying 

 squirrels and other rodents of old-growth hab- 

 itat. Its decline in a region is considered a sig- 



Ptioto credit: Chesapeake Bay Foundation 



Rockfish, once abundant in the Chesapeake, have been 

 exploited and are now endangered in many areas of the 

 estuary. The decline in population of this highly valued 

 species has been attributed to overfishing and pollution. 



