Extinction and Endangered Species - Mass Extinction

In the billions of years since life began on Earth, species have formed, existed, and then become extinct. Scientists call the natural extinction of a few species per million years a background, or normal, rate. When the extinction rate doubles for many different groups of plants and animals at the same time, this is described as a mass extinction. Mass extinctions have occurred infrequently in Earth's history and, in general, have been attributed to major cataclysmic geological or astronomical events. Five mass extinctions have occurred in the last 600 million years. These episodes, known as the Big Five, occurred at the end of five geologic periods—the Ordovician (505–440 million years ago), Devonian (410–360 million years ago), Permian (286–245 million years ago), Triassic (245–208 million years ago), and Cretaceous (146–65 million years ago). After each mass extinction, the floral (plant) and faunal (animal) composition of the Earth changed drastically. The largest mass extinction on record occurred at the end of the Permian, when an estimated 90–95 percent of all species went extinct. The Cretaceous extinction is perhaps the most familiar—it was at the end of the Cretaceous that many species of dinosaurs went extinct. The Cretaceous extinction is hypothesized to have resulted from the collision of an asteroid with the earth.

The Sixth Mass Extinction?

According to biologists, plant and animal species are now disappearing at a rate of one per day. This suggests that we are currently in the midst of another mass extinction. Unlike previous mass extinctions, however, the current extinction does not appear to be associated with a cataclysmic physical event. Rather, the heightened extinction

TABLE 1.1
Extinct species in Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin
These are some of the animals that were once part of the fauna in this region but are now extinct.

Mammals

Eastern Elk (Cervus canadensis canadensis) Formerly found in: United States east of Great Plains Extinct in 1880

Birds

Carolina parakeet (Conuropsis carolinensis carolinensis) Formerly found in: Southeastern United States Extinct about 1920

Heath Hen (Tympanuchus cupido cupido) Formerly found in: Eastern United States Extinct in 1932

Passenger Pigeon (Ectopistes migratorius) Formerly found in: Central and eastern North America Extinct in 1914

Fish

Blackfin cisco (Coregonus nigripinnis) Formerly found in: Lakes Huron, Michigan, Ontario, and Superior Extinct in 1960s

Blue pike (Stizostedion vitreum glacum) Formerly found in: Lakes Erie and Ontario Declared extinct in 1983

Deepwater cisco (Coregonus johannae) Formerly found in: Lakes Huron and Michigan Extinct in 1960s

Harelip sucker (Lagochila lacera) Found in a few clear streams of the upper Mississippi Valley; Scioto River in Ohio; Tennessee River in Georgia; White River in Arkansas; Lake Erie drainage, Blanchard and Auglaize Rivers in northwestern Ohio Not seen since 1900

Longjaw cisco (Coregonus alpenae) Formerly found in: Lakes Erie, Huron, and Michigan Declared extinct in 1983

Shortnose cisco (Coregonus reighardi) Formerly found in: Lakes Huron, Michigan, and Ontario No individuals collected since 1985

Clams

Leafshell (Epioblasma flexuosa) Formerly found in: Alabama, Illinois, Indiana, Kentucky, Ohio, Tennessee Has not been found alive in over 75 years and since 1988 has been considered extinct

Round combshell (Epioblasma personata) Formerly found in: Illinois, Indiana, Kentucky, Ohio Has not been found alive in over 75 years and since 1988 has been considered extinct

Sampson's pearlymussel (Wabash riffleshell) Epioblasma sampsonii Formerly found in: Illinois, Indiana, Kentucky Declared extinct in 1984

Scioto pigtoe (Pleurobema bournianum) Formerly found in: Ohio

Tennessee riffleshell (Epioblasma propinqua) Formerly found in: Alabama, Illinois, Indiana, Kentucky, Ohio, Tennessee Has not been found alive in over 75 years and since 1988 has been considered extinct

rate has coincided with the success and spread of human beings. Researchers predict that as humans continue to alter natural ecosystems through destruction of natural habitats, pollution, introduction of non-native species, and global climate change, the extinction rate may eventually

TABLE 1.1
Extinct species in Illinois, Indiana, Iowa, Michigan, Minnesota, Missouri, Ohio, and Wisconsin
These are some of the animals that were once part of the fauna in this region, but are now extinct.

Plants

Bigleaf scurfpea (Orbexilum macrophyllum) Formerly found in: Indiana and Kentucky

Thismia americana (no common name) Found in Illinois Last seen in 1916; declared extinct in 1995

SOURCE: Extinct Species, in U.S. Fish and Wildlife Service Region 3: Endangered Species, U.S. Fish & Wildlife Service, Fort Snelling, MN, 2004 [Online] http://midwest.fws.gov/Endangered/lists/extinct.html [accessed February 24, 2004]

approach several hundred species per day. This would be a rate millions of times higher than normal background levels. The Worldwatch Institute, a think tank devoted to environmental issues, has suggested that, without effective intervention, more species of flora and fauna may disappear in one human lifetime than were lost in the mass extinction that wiped out the dinosaurs 65 million years ago.

The World Conservation Union (IUCN) reports that in the last 500 years, at least 816 species are known to have gone extinct as a result of human activity. The actual number is probably much higher. Table 1.1 lists some U.S. animal and plant species that are now extinct from the midwestern United States.