What are the different types of extinction?

We all know that dinosaurs are extinct. Unless you count their closest living relatives, birds like chickens! Extinct means that a species has died out. This could have been caused by environmental factors like climate change. It could also have been caused by evolution and inbreeding. There’s the kind of extinct that refers to prehistoric plants and animals, like dinosaurs. In fact, the majority of species that ever lived are now extinct. Extinctions may occur all at once, a mass extinction, like the die-off of the dinosaurs. More commonly though, extinction occurs gradually, in what’s known as a background extinction. These natural extinctions are also different from extinctions caused by modern humans. The current rate of human-caused extinction is 1,000 times greater than past background extinctions. This is mostly due to habitat loss and overharvesting. Species that have gone extinct because of humans include Tasmanian tigers, passenger pigeons, dodo birds, and Maracay harlequin frogs. The first step in extinction is depletion: the species is disappearing faster than new members are born. Once a species is depleted, it can become ecologically or functionally extinct. This means that the animal doesn’t play a role in the ecosystem any longer. Species are interdependent, so the loss of one affects others. For example, the disappearance of wolves in the American West allowed the number of coyotes to increase. That caused a decrease in the number of rabbits, as the coyotes preyed upon them. A species can also be commercially extinct. These animals exist in too small a quantity to be profitably pursued. This term usually refers to fish, like Atlantic cod off the coast of Canada. Fishing operations harvested thousands of pounds of cod per day for years. After decades of overfishing, the cod population couldn’t recover. A species can also be extinct in the wild but alive in captivity, like some species of frogs. Captive breeding is often done as part of conservation efforts. There is hope that animals kept alive this way can someday be reintroduced to their native habitats.