464 Natural Resources Systems Copyright Goodheart-Willcox Co., Inc. A species that is extinct is a species that is no longer living. Species extinction occurs naturally at a background extinction rate of about one to five species per year. These background extinctions are due to normal environmental changes, such as a volcanic eruption or increased competition and failure to adapt. This low rate of extinction allows other species in an ecosystem to adapt to the changes that occur when an organ- ism is removed from an ecosystem. Today, however, scientists estimate the extinction rate is thousands of times the background rate and we are los- ing approximately 1000 species each year. This rate will increase as species disappear because each species’ extinction has the potential to lead to the extinction of others. Almost every species currently in danger of extinction is threatened because of our actions, primarily the destruction of habitats. Global climate change and the introduction of invasive species are also key factors. In this chapter, we will discuss how threatened species are classifi ed, causes of spe- cies extinction, and efforts used to slow the extinction rate. International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN) is an environmen- tal organization dedicated to global conservation. The IUCN works with pri- vate, public, and nongovernmental organizations to develop ways in which conservation and sustainable development can take place together. In 1948, the initial goal of the IUCN was to examine how human activities affected the environment. In the 1960s and 1970s, the IUCN focused on the protection of species and habitats that were necessary for their survival. In 1964, the IUCN established the IUCN Red List of Threatened Species™, Figure 19-1. The IUCN Red List currently includes more than 26,000 endangered species from around the world. Before You Read Choose three animals on IUCN Red List. What do they have in common? What do you know about the history of these animals? Research the animals and learn about their history and status. Use this information to contribute to class discussions. Figure 19-1. One of the animals on the IUCN’s first Red List (1964) for endangered species is the southern hairy-nosed wombat (Lasiorhinus latifrons). This species is native to Australia and is currently listed as least concern (LC) on the IUCN Red List. Steve Lagreca/Shutterstock.com The IUCN’s current members include 219 state and government agencies and more than 1100 nongovernmental organizations. More than 13,000 experts volunteer in over 160 countries to perform research and assessments of the state of the world’s natural resources. Did You Know?