With the evolution of human beings, many species of animals and plants also evolved. Some species of animals and plants started to extinct as the world went from rural to urban and industrialized. Because of pollution and other environmental factors, many species felt threatened to die out. Threatened Species are those that are expected to be endangered in near future. It may happen that a portion of the specific specie is at stake or the whole specie is vulnerable to risk in foreseeable future. Threatened species are also said vulnerable species and both can be interchangeably used in daily life.
The World Conservation Union is the first international organization that started to work for saving these vulnerable species that are threatened by environment. The organization tries to evaluate the decreasing number of the species with the help of critical depensation level. It is the level where biologists come to know that the respective species cannot sustain for a long time.
These vulnerable kinds of species are also referred as red listed species. Red species include native species and sub-species (sub species are also called Taxa) which are on the verge of extinction in a few years in some locality. But it may happen that they extinct in one locality but can be found in some other place, whole extinction is not inevitable. Red listed species can be saved from extinction if some depleting factors are reserved. If the required environment is saved for these vulnerable species, then they can be protected for a longer time.
The factors are many for danger to the species. Reckless hunting of birds and animals, deforestation, pollution, etc. are every day seen causes of species extinction. Passenger pigeon and golden toads are examples that extincted because of hunting and environmental changes as well. Deforestation and pollution have forced the parrots and sparrows to leave the cities and many died because of the same factors. These species are definitely threatened to be wiped out from the wild life in near future. Recently US District judge has listed the polar bear a threatened animal rather than an endangered one on the planet. Polar bears are expected to extinct in near future as they spend their lives on ice and the ice is melting because of global warming. The lives of polar bears are at stake in coming days, although the process is gradual.
Reference: Illustrated Encyclopedia of endangered animals.
