Four hundred and thirty-eight million years ago the first of five mass extinctions hit Earth. During the Ordovician-Silurian extinction 25 percent of marine families and 60 percent of marine genera were lost.
Following this period, paleontologists believe an episode of global cooling wiped out 57 percent of marine genera and 22 percent of marine families during the Devonian extinction.
About 254 million years ago the Permian-Triassic extinction developed and killed off 95 percent of all species, 53 percent of marine families, 84 percent of marine genera and 70 percent of land species like plants, insect and vertebrate animals. Scientists believe a volcanic eruption within the Siberian Traps coated large sections of land with lava reducing the amount of oxygen in the air which resulted in mass extinction.
Between 199 million and 214 million years ago during the Triassic period, 22 percent of marine families, 52 percent of marine genera and an unknown percentage of vertebrae died because of global warming. Volcanic eruptions across the central Atlantic magmatic province and eruptions in the eastern United States, eastern Brazil, North Africa and Spain spread rocks and lava across the continents destroying life.
The fifth extinction period, called the Cretaceous period, occurred 65 million years ago and is believed to be from asteroid impacts that created the Chixulub crater hidden on the Yucatan Peninsula beneath the Gulf of Mexico. During this extinction period, 16 percent of marine families, 47 percent of marine genera and 18 percent of land vertebrae families, including dinosaurs, died.
The sixth extinction is underway, now, with animals going extinct up to 1,000 times faster than the normal extinction rate. This means we are losing 10 to 25 species per year. Researchers unofficially claim we are in the middle of the extinction period is more destructive than the Cretaceous-Tertiary extinction that wiped out the dinosaurs. The five major problems humans are creating around the world causing this contemporary extinction:
- Habitat Destruction created by greenhouse gas emissions
- Invasive species moving into other habitats creating predation, competition and disease organisms
- Pollution
- Human overpopulation
- Over-harvesting, a direct cause of hunting, fishing and gathering
In the last 25 years, 120 species have become possibly extinct. Nearly 1,800 species of amphibians are currently threatened everywhere because of habitat loss and degradation.
Examples of endangered amphibians are:
- Chinese Giant Salamander in China
- Western Nimba Toad in Guinea and Ivory Coast
- Oki Salamander in Japan
- Mountain Mistfrog in Australia
Twelve percent of all living bird species are considered endangered, threatened or vulnerable. For many it is too late but we can still save others by taking action against global climate change, supporting legislation that reduces greenhouse gases and not polluting our environment.
- Alaotra Grebe in Madagascar
- Azores Bullfinch in the Azores, Portugal
- Chatham Albatross in the southern Pacific, Chile and Peru
- Southern Ground-hornbill in South Africa
Around 26,800 aquatic vertebrates are classified as fish living in fresh and saltwater environments throughout the world. Forty percent of them were classified in 2007 as being threatened on the endangered species list. In Europe alone one in three freshwater fish species are threatened with extinction.
- Clarion Angelfish around the Revillagigedo Islands, Mexico
- Bravo Clinid in the Galapagos and Malpelo Islands
- Atlantic Sturgeon in the North Sea, north-eastern Atlantic, Mediterranean coasts of Europe and the Black Sea
- Sterlet in the Black, Azov and Caspian Seas
Over 97 percent of animal species are invertebrates including insects, spiders, crustaceans, squid, sponges, flatworms and starfish. According to International Union for Conservation of Nature and Natural Resources (IUCN) over half of all invertebrates are now listed as threatened or endangered. The major reason invertebrate species disappear is loss of habitat. Presently crustaceans account for the highest losses in this classification.
- Stone Crayfish in France, western Germany and Turkey
- Goldstreifiger in Ukraine, Spain, Germany, Austria and Sweden
- Blue River Crab in northeastern Kwa-Zulu Natal, Africa
- Sudeten Riglet in France, Switzerland, Czech Republic and Romania
Middle ear bones, hair and the production of milk are three characteristics shared by mammals. The World Conservation Union determined in 2007 that 1,093 mammal species are threatened because of habitat destruction and fragmentation, human-induced climate change and over-hunting.
- Giant Armadillo in South America
- Nelson's Small Eared Shrew in Volcan San Martin Tuxtile in Veracruz, Mexico
- Dingiso in Island of New Guinea
- Rothschild's Giraffe in Murchison Falls National Park, Uganda and Kenya
8,700 species of reptiles exist around the globe. On the IUCN Red List of Threatened Species there are 180 species classified as data deficient. Of the worldwide population thirty-five percent of reptiles have been evaluated and listed on the list as a threatened species. Of this 35 percent, 203 species are classified as Vulnerable, 134 as Endangered and 86 as Critically Endangered.
- Lyre Head Lizard in Sri Lanka
- Lesser Antillean Iguana in the northern Lesser Antilles, Saint-Martin, St Kitts, Nevis, Antigua and Barbuda
- Yunnan Box Turtle in China
- Yellow-bellied Sea Snake in the tropical Pacific and Indian Oceans