Environmental Problems, Their Causes, and Sustainability 1

12 TheSustaining Biodiversity:Species ApproachBiodiversityCASE STUDYThe Passenger Pigeon:Gone ForeverIn 1813, bird expert John James Audubon saw a singleflock of passenger pigeons that he estimated was 16kilometers (10 miles) wide and hundreds of kilometerslong, and contained perhaps a billion birds. Theflock took three days to fly past him and was so densethat it darkened the skies.By 1914, the passenger pigeon (Figure 12-1) haddisappeared forever. How could a species that wasonce the most common bird in North America andprobably the world become extinct in only a fewdecades? The answer is, humans wiped them out. Themain reasons for the extinction of this species wereuncontrolled commercial hunting and loss of thebird’s habitat and food supply as forests were clearedto make room for farms and cities.Passenger pigeons were good to eat, their feathersmade good pillows, and their bones were widelyused for fertilizer. They were easy to kill because theyflew in gigantic flocks and nested in long, narrowcolonies.Commercial hunters would capture one pigeonalive, sew its eyes shut, and tie it to a perch called astool. Soon a curious flock would land beside this“stool pigeon”—a term we now use to describe someonewho turns in another person for breaking the law.Then the birds would be shot or ensnared by nets thatmight trap more than 1,000 birds at once.Beginning in 1858, passenger pigeon hunting becamea big business. Shotguns, traps, artillery, andeven dynamite were used. People burned grass orsulfur below their roosts to suffocate the birds. Shootinggalleries used live birds as targets. In 1878, oneprofessional pigeon trapper made $60,000 by killing 3million birds at their nesting grounds near Petoskey,Michigan!By the early 1880s, only a few thousand birds remained.At that point, recovery of the species wasdoomed because the females laid only one egg per nesteach year. On March 24, 1900, a young boy in Ohioshot the last known wild passenger pigeon. The lastpassenger pigeon on earth, a hen named Martha afterMartha Washington, died in the Cincinnati Zoo inJohn James Audubon/The New York Historical SocietyFigure 12-1 Lost natural capital: passenger pigeons have beenextinct in the wild since 1900. The last known passenger pigeon diedin the Cincinnati Zoo in 1914.1914. Her stuffed body is now on view at the NationalMuseum of Natural History in Washington, D.C.Eventually all species become extinct or evolveinto new species. But biologists estimate that humanactivities have increased the natural rate of extinctionby a factor of 1,000 to 10,000—perhaps more. Studiesindicate that this rate of loss of biodiversity is expectedto increase as the human population grows,consumes more resources, disturbs more of the earth’sland and aquatic systems, and uses more of the earth’snet plant productivity that supports all species.