The world's animal resources have changed tremendously over time.  In modern times, high levels of extinction have increased the level of loss of the world's animals.

Modern science has identified 1.7 million different species of plants and animals.  Most of these are insects.  In total, the number of species inhabiting the planet may be in the tens of million, but estimates are continually changing.

A Lizard.  Photo Credit: ClickART Image Pak.

Many species that currently inhabit our planet may be lost without people ever knowing them.  Destroying tropical rain forests and other ecosystems can cause widespread extinction of species.

Once, passenger pigeons were the most numerous animals on the North American continent.  Billions of the birds may have lived there, until hunters from the United States began to decrease the pigeon population.  By 1914, the species was completely gone due to massive habitat destruction and commercial hunting.

This is just one of many ways that an animal species can go extinct.  Habitat destruction, hunting, pest and predator control, removing animals from the wild, pollution, and introduction of exotic creatures can all lead to extinction.

Many people seek to preserve the world's animal resources for many reasons.  There are economic, health, aesthetic, recreational, ecological, and ethical reasons why people should not act in a way that promotes extinction.

Those in favor of preserving animal resources have taken action.  Laws, zoos, and preservation all serve to help the world keep the animal species that are left.