When was the last time that you had a dinosaur cross through your back yard? Have you seen any woolly mammoths strolling the streets lately? We can't see these creatures, because they are extinct!
When a species becomes extinct, it is gone forever. Throughout earth's history, that's been a part of nature's story — plants and animals are born and die. And that is just as true for whole species as it is for individual members.
Scientists think there is a natural rate at which species come and go. So if extinction is a natural process, what's the problem? These days, species are going extinct faster than expected. And in many cases scientists think they are dying off because of human actions.
Before a species becomes extinct, there are usually warning signs. If we watch for the warning signs, there is the possibility of preventing plants and animals from going away forever.
In the United States, we group the loss of species into three levels of concern: threatened, endangered and extinct. These groupings come from the 1973 Endangered Species Act.
When a species is threatened, it is a warning that there is a problem of some kind that puts its survival at risk. How do scientists decide that a species is in danger?
Basically, they look at the number of species members in a particular area (habitat) and compare them over time. For example, how many salmon were there 100 years ago in the Snake River versus how many in the same river today? And they study what a species needs to live and survive. For example, what kind of foods do they eat? How much space do they need? What kinds of plants, animals, landscape features and climate are in their habitat? Scientists compare these things over time too. If anything has changed drastically — the number of species members is way less than it used to be, a food source is not as plentiful, water sources have dried up, migration paths are blocked, and so forth — then scientists know that a species may already be struggling to survive or might do so in the future.
If too many members of one species are lost and their numbers get severely low, or if conditions make it hard for survival of a species over time, they are considered endangered. Animal populations that dwindle even in just one region or country can be listed as endangered for just that area. Animals or plants that are considered to be endangered have the possibility of becoming extinct and need immediate attention and protection.
As of January, 2016, the U.S. Fish and Wildlife Service lists 2,244 plants and animals as threatened or endangered worldwide. This includes 1,590 plants and animals in the United States. Check current numbers.
These lists are important. When a species is listed, it means that the plants and animals are protected by laws or groups who fight and work for their survival. Check out these laws. While this might sound impressive, these numbers only represent the plants and animals that are known. Most plant and animal species that could actually be endangered are not on the list because they are not yet identified.
As of 2011, scientists had only identified about 1.3 million species in the world. Estimates of how many total species there are range from 3 million to 100 million. Many tiny species such as microbes like bacteria haven't even been discovered yet. So thousands of species may become extinct every year without us even knowing they exist.
There are many reasons species become endangered. These include such things as habitat loss, competition from other species for food and other resources, pollution, pesticides and other environmental factors, over-hunting, and disease.
Development by humans can also impact a species, by causing changes in their physical habitat. Whenever we build a new subdivision, we change the habitat that was used by rodents, snakes, birds, amphibians, insects, and lots of other wildlife. These habitat changes impact food chains and food webs. And did you know that the introduction of non-native species — like your pets — can be harmful too? If they become predators of a native species, they can!
Once a plant or an animal is extinct there is no way to reverse this. An extinct species is gone forever.
Since the 1600s, more than 700 species of known plants and animals have gone extinct. There is no way of knowing how many undiscovered treasures have been lost to extinction. In one month, it is estimated that between 30 and 1,400 species disappear. In one day alone, we can say good-bye to at least one plant or animal species. Again, this is only counting the plants and animals that we know of.
How does extinction happen? Species disappear because of changes to the earth that are caused either by nature or by the actions of people. Sometimes a natural event, like a volcano erupting, can kill an entire species. Other times, extinction happens slowly as nature changes our world. For example, after the Ice Ages, when the great glaciers melted and the earth became warmer, many species died because they could not live in a warmer climate. Newer species that could survive in a warmer environment took their places.
Earth has seen at least five great extinction periods, each wiping out up to 95 percent of all living species. These extinctions involved massive volcanic eruptions, disastrous meteor strikes and rapid climatic changes. It is unknown when the next great extinction will be or what its cause will be.
For a long time, people didn't realize how much their actions impacted the environment or that they could cause so much damage to plants and animals. Today, many species are endangered or threatened not for natural reasons but because people have changed the habitats upon which these species depend. Here are some examples of how human behavior has threatened wildlife:
Pesticides and other chemicals are used to rid crops of damaging insects, pests or weeds. But they can also poison desired plants and animals if they are not used correctly. The bald eagle is one bird that was harmed by pesticides. In the past, a pesticide called DDT was used by many farmers. Rains washed the pesticide into the lakes and streams where it poisoned fish. After eating the poisoned fish, the eagles would lay eggs with very thin shells. These eggs were usually crushed before they could hatch. Today, people are not allowed to use DDT and the bald eagle, although once endangered, has been taken off the endangered species list. What a great success.
People can also endanger plants and animals by introducing new species into areas where they do not naturally live. Some of these species do so well in their new habitat that they endanger those species already living there, called the native species. For example, when some fish are introduced into a lake or stream, they may prey upon the native fish or eat their food. The native species may then have to find a new source of food or a new home. Otherwise they could face becoming endangered or extinct.
Hunting is also a major cause of endangerment. In the past, American crocodiles were killed so that their skins could be made into shoes and other clothing. They were also hunted as food, for sport and out of fear. Many have been impacted by climate change, habitat loss, and other factors. The American crocodile is now an endangered species in many parts of the Western Hemisphere. But due to important protection efforts the animal has been relisted as threatened in the state of Florida.
Classifying Endangered and Threatened Species
In the United States, the U.S. Fish and Wildlife Service (FWS) decides which species are threatened and which are endangered through its listing program. The review process starts when someone, and it could be anyone, sends a petition to the U.S. Fish and Wildlife Service. The petition asks the FWS to find out if there is evidence that the species is on the edge of extinction. A species will be classified as endangered if there is enough scientific evidence to prove a need. There are other groups around the world who classify species outside of the U.S. One of the most important is the International Union for Conservation of Nature (IUCN). See their Red List of Threatened Species.
Once a species has been identified as threatened or endangered, then a plan must be made to help return things to normal or as close to normal as possible. These plans are known as recovery plans. Recovery plans are created to prevent endangered plants and animals from becoming extinct. The recovery plans attempt to make the species stable, increase their numbers, and resolve the issues that put them on the list in the first place.
A number of actions go into saving these creatures. Actions may include limiting the ability to hunt them, passing laws about use of pesticides, protecting the habitat they live in, and even placing some of them in zoos where they are cared for by humans before being returned to the wild.
Unfortunately, recovery plans aren't always successful. But in a number of instances they have been very effective. The animal or plant that is no longer in danger is then delisted or removed from the threatened or endangered species list. That means that there are now a significant number of members of the species and they are thriving and doing well. The National Wildlife Federation has some amazing success stories that tell how species in the United States have been brought back from near extinction and delisted. You may want to check these out.
Bald Eagles — America's Bird . . . and a true success story!
In 1963 there were only about 417 nesting pairs of bald eagles in the United States. Today there are about 9,789 nesting pairs. In 2007 this wonderful bird was delisted from the threatened and endangered species list. We can make a difference!
Some Animals That Are Currently Endangered
Bactrian Camel — The Bactrian Camel is known for its two humps and lives in China and Mongolia. They store water in their humps and can go for long periods of time without need to consume fresh water. They live in small herds of up to about 100 members. Learn more . . .
Orangutans — Orangutans are highly intelligent observers. They have been known to watch humans untie a boat and row it across a river, and then repeat the behavior themselves. Like humans, orangutans pass down socially learned traditions. For example, the orangutans in Borneo use leaves as napkins to wipe their mouths, and orangutans in parts of Sumatra use leaves as gloves when handling thorny branches. The orangutans from Sumatra are considered highly endangered. Learn more . . .
The Yellow-Eyed Penguin — The most endangered penguin in the world is the yellow-eyed penguin, which inhabits the coasts and offshore islands of southeast New Zealand. The yellow-eyed penguin population is estimated at less than 7,000. Learn more . . .
Florida Panther — The Florida Panther is one of the world's most endangered species. This amazing cat marks its territory with scrapes (piles of soil, leaves, or pine needles). Sometimes they even mark their territory by putting urine or feces on top of the scrapes to let others know to keep off their turf! Florida panther kittens and their mothers keep track of each other with whistles. Learn more . . .
The Javan Rhinoceros — The Javan Rhinoceros is the least known of the five species of rhinoceros alive on the earth today. This may be because of its low population. They are mainly found within the Ujung Kulon National Park in Java, and they prefer lowland rainforests, large flood plains with mud wallows, and tall grasses. Learn more . . .
Why Should We Care?
It's easy to feel upset about the loss of well-known animals like pandas, tigers, or whales. But the real danger is losing all the plants and creatures that aren't so cute or well-known.
Plants and animals serve many beneficial purposes to humans, including medicinal, agricultural, ecological, commercial, aesthetic and recreational. For example, about 40% of our medicine is made from things found in nature, and we have only explored about 5% of the known plant species for medicines. Hidden in nature — maybe thriving, maybe disappearing — may lie a cure for cancer or some other disease.
But, as beneficial as many species are to humans, all of them are important to their ecosystems as a whole. Death to a large population of a plant or animal species can cause changes in the food web to which it belongs. This, in turn, upsets the biodiversity of its habitat. For example, many of our food crops depend on bees to pollinate them and produce seeds. So the recent decline in bee colonies may prevent those plants from propagating if enough bees aren't available to carry pollen from one plant to another. And the loss of plants that depend on pollinators could in turn affect other living creatures that depend on those plants for food or shelter. And so forth . . .
Species need to be protected and saved so that all of earth's different habitats can thrive, and future generations can enjoy their presence and experience their value.