Chapter
1
By Susan Stempleski
When people hear the word endangered, most of them think of a large and majestic species, like the Asian elephant, or a cute and cuddly one, like the giant panda. While these creatures are indeed endangered, the threat of extinction is not limited to the few species we can recognize in pictures or on visits to zoos. The threat of extinction affects nearly every species on the planet.
Endangered Species has been selected as the theme of the first chapter of the Environmental Education volume because of its universal importance and its interest to students. By learning about some animal and plant species that are in trouble, students can discover why we need to protect all the species on the planet, including the ones that are not as cute as pandas or as majestic as elephants. Learning about endangered species is important for other reasons too. By examining the problems of endangered species, students can begin to appreciate the crucial role of habitat protection.
While reading about and discussing endangered plant and animal species, students improve their language skills by learning and using new vocabulary and concepts associated with the topic. The topic is a broad one and can be exploited in a variety of ways. Some teachers may decide to use the activities described in the section on Classroom Applications as a single 50-minute lesson. Others may choose to combine some of the materials outlined in the section on Internet Resources to create a more extensive teaching unit. The ideas presented here are offered only as a starting point for introducing the study of endangered species to students.
Most people have a general idea of what an endangered, threatened, or extinct species is, but biologists have rather precise definitions for each term. An endangered species is a type of animal or plant that is in immediate danger of extinction. The species usually has a small population and needs protection in order to survive. The mountain gorilla, the Indian python, the lady slipper orchid, and thousands of other plant and animal species throughout the world are endangered.
Biologists use the word threatened to describe species that face serious problems, but whose populations are not in immediate danger of becoming extinct. Some examples of threatened species are the African elephant, the northern spotted owl, and the eastern indigo snake.
Extinct species no longer exist or live anywhere in the world. The dodo, the passenger pigeon, and the dinosaurs are examples of extinct species.
An Old Phenomenon
Extinction is not a new phenomenon. For hundreds of millions of years, extinction has been occurring naturally, as part of the evolutionary process. Some cases of extinction have been caused by natural disasters, such as volcanic eruptions. Others have been the result of environmental changes, such as shifts in climate. Sometimes extinction occurs on a very large scale, with hundreds or thousands of species becoming extinct over a relatively short period of time. An example of this is the dinosaurs and their contemporaries, victims of a mass extinction that took place at least 65 million years ago.
An Increasing Rate of Extinction
Although extinction itself is not an old phenomenon, the current rate of extinction is something new. Biologists say that at least three animal and plant species become extinct every day, a rate much higher than anything in the past 65 million years.
Why Species Become Endangered
Species become endangered for a wide variety of reasons. However, when individual cases are grouped and studied, the same broad causes appear again and again:
Rapid habitat destruction is the main reason that species become endangered. Natural changes usually occur at a slow rate, so the effects on individual species are usually slight, at least over the short term. When the rate of change is greatly speeded up, there may be no time for individual species to adapt to new conditions. The results can be disastrous. This increase in the rate of habitat destruction is directly linked to the rise in human population. As more people use more space--for homes, farms, shopping centers, and so on--there is less living space for species that cannot adapt to changing conditions. People also affect plant and animal habitats when they take wood, oil, and other products from the land.
Another people-related problem that harms wildlife is the introduction of exotic species - foreign species that are deliberately or accidentally introduced into new habitats by human activities. Sometimes an introduced species causes no obvious harm, but in other cases the introduced species causes serious problems. The worst of these problems is when introduced species begin to prey on native species and cause them harm.
Overexploitation is another reason species become endangered. One example of this is the case of the great whales, many of which were reduced to extremely low populations sizes in the mid-20th century because of unrestricted whaling. In 1982 a number of countries agrees to put a ban on commercial whaling. As a result, some whale species that used to be endangered have made great comebacks. Many other species, however, are still at risk. Some other animal species experience high rates of exploitation because of the trade in animal parts. Currently, this trade is centered in several parts of Asia where there is a strong market for traditional medicines made from items like tiger bone and rhino horn. Other people-related problems that put plant and animal species at risk include poaching, pollution, and overcollecting.
