Overexploitation

Overexploitation of the biosphere by hunting, fishing or logging produced extinctions in the past and will lead to more in the future. We will deal with just a few of the species that have already been lost to overexploitation, or are endangered today.

Steller's sea cow

 

stellers-sea-cow
Public Domain, Widimedia Commons
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Sea cows are sea mammals that include living species of manatee and dugong. They are herbivores that feed on sea grasses. Steller's sea cow was a large species that was discovered in 1741 in the coastal waters of the Commander Islands, about 100 miles off the Kamchatka Peninsula of far eastern Russia. By 1768 it was extinct. Russian fur hunters (hunting sea otters, which were nearly driven to extinction themselves) used the sea cow as a source of food. Historical records show that the sea cow was easy to catch using harpoons, and hunters took more than they could eat.

Passenger pigeon

 

passenger-pigeon-named-martha
Public Domain
passenger-pigeon-shooting-in-louisiana_smith-bennett_1875
Public Domain

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The last passenger pigeon died in Cincinnati Zoo in 1914, but the wild population measured in billions in the 18th and 19th centuries. The species lived throughout the eastern half of the United States and southeastern Canada, although it bred mostly in forests of the northeast. It fed mostly on acorns, beechnuts and chestnuts. The passenger pigeon was hunted in large numbers. Historical records show that in 1871, 1.2 million birds were killed in central Wisconsin alone. As the population size was so large, hunting was not the sole cause of extinction of the species. Clearing of forests for agriculture and other purposes led to habitat loss and that also reduced pigeon populations. Extinction of the passenger pigeon seems to have influenced other species. The acorns of the north red oak were an important food source for the pigeon during the breeding season. Following the extinction, increased survival of acorns may be one factor that caused an expansion of the northern red oak.