What makes endangered species

And yet in a surprising twist, Los Angeles, a city and its suburbs home to 19 million people is an enclave where mountain lions live side-by-side with humans [9]. Mountain lions have been roaming the city for at least 30 years and The National Park Service has been studying them since , curious how mountain lions survive in an increasingly fragmented and urbanized landscape [10].

A recent citing prompted this response from a year old resident. On the other hand, as our populations increase and more people move into areas where wildlife previously lived in abundance, new human-wildlife conflicts arise. Sadly, in many cases, wildlife is killed when they cause too big harm to farmers by hunting livestock or destroying crops. For wildlife populations that have already been reduced due to loss of habitat and other issues, such conflicts can increase the chances that a species will become threatened or endangered.

Diseases kill humans and animals alike. The Ebola virus killed 5, critically endangered western gorillas between and at the Lossi Sanctuary and other hundreds of gorillas in the Odzala-Kokoua National Park in [12]. A deadly fungus from Europe, where it is harmless to bats has spread to North America killing 6 million bats and taking many species to the brink of extinction. It was a fungus that destroyed the American chestnut tree, one hundred-foot hardwoods that once numbered in the billions in eastern forests of the United States, and a significant food source for a variety of wildlife, but which were virtually eliminated by a fungal pathogen accidentally imported into the United States from Asia [14].

Because the American Chestnut tree had evolved in conditions without the presence of the fungus, it lacked the natural resistance to survive. Currently, there is ongoing research with the aim of creating a hybrid chestnut variety that is a cross between the American Chestnut and a variety of Chinese chestnut that is resistant to the chestnut fungus. It is believed that reproduction rates are a natural way of maintaining a population equilibrium. Some species do not reproduce very often, and they may have few offspring each time when they breed.

Other species may take a number of years to become sexually mature, thus reducing their opportunity to breed over their lifetime. Generally, larger mammals have longer lifetimes and lower birth rates and smaller animals like rodents who do not live as long produce many litters in succession [15].

Consequently, when large mammals suffer man-induced mortality, it takes longer for their populations to recover. A good example are marine mammals whose populations were diminished by commercial exploration.

If a population has low genetic variation, it cannot evolve on the face of changing environmental variables and will face an increased risk of extinction. For example, if a population does not have a gene that is resistant to a certain disease, that disease may wipe out the entire population in one fell stroke [17]. Some species, such as the Cheetah, maintain low genetic diversity, which makes them less able to adapt when faced with challenges such as overhunting or habitat loss.

This low genetic diversity also makes them more vulnerable to diseases and expressions of negative genetic mutations. Koalas are known to have low genetic variation [18]. This may be why they are showing high vulnerability to Chlamydia and the koala retrofit virus. Their vulnerability may also make it more difficult for koalas to adapt to global warming and human encroachment of their habitats.

Some species can be found only in certain areas. If there are only a limited number of individuals of a species that are in existence to begin with, and the environment changes, there is a lower probability that such a species will survive in the future. Rare species can easily become extinct in the face of hunting.

The Sumatran Tiger is an example of a rare species that was over hunted to the point of extinction, as there were a very limited number of individuals to begin with. There are only 1, ili pika, a tiny mammal living in a remote mountain range in China. Rising temperatures have forced them to the mountain tops. They have healthy populations, but their rain forest habitat is disappearing at a fast pace.

People are cutting down huge areas of rain forest for development and timber. Many violet species are likely to become threatened. Vulnerable Species The definitions of the three threatened categories vulnerable, endangered, and critically endangered are based on five criteria: population reduction rate, geographic range, population size, population restrictions, and probability of extinction. Threatened categories have different threshold s for these criteria.

As the population and range of the species decreases, the species becomes more threatened. This decline is measured over 10 years or three generations of the species, whichever is longer. A generation is the period of time between the birth of an animal and the time it is able to reproduce. Mice are able to reproduce when they are about one month old. Mouse populations are mostly tracked over year periods. An elephant's generation lasts about 15 years. So, elephant populations are measured over year periods.

A species is vulnerable if its population has declined at least 50 percent and the cause of the decline is known. Habitat loss is the leading known cause of population decline. A species is also classified as vulnerable if its population has declined at least 30 percent and the cause of the decline is not known.

A new, unknown virus, for example, could kill hundreds or even thousands of individuals before being identified. An area of occupancy is where a specific population of that species resides. This area is often a breeding or nesting site in a species range. The species is also vulnerable if that population declines by at least 10 percent within 10 years or three generations, whichever is longer. A species is vulnerable if it is restricted to less than 1, mature individuals or an area of occupancy of less than 20 square kilometers 8 square miles.

These formulas calculate the chances a species can survive, without human protection, in the wild. Vulnerable Species: Ethiopian Banana Frog The Ethiopian banana frog Afrixalus enseticola is a small frog native to high- altitude areas of southern Ethiopia. It is a vulnerable species because its area of occupancy is less than 2, square kilometers square miles.

The extent and quality of its forest habitat are in decline. Threats to this habitat include forest clearance, mostly for housing and agriculture. Vulnerable Species: Snaggletooth Shark The snaggletooth shark Hemipristis elongatus is found in the tropical , coastal waters of the Indian and Pacific Oceans. Its area of occupancy is enormous, from southeast Africa to the Philippines, and from China to Australia.

However, the snaggletooth shark is a vulnerable species because of a severe population reduction rate. Its population has fallen more than 10 percent over 10 years. The number of sharks is declining due to fisheries, especially in the Java Sea and Gulf of Thailand. They are sold in commercial fish markets, as well as restaurants. Galapagos kelp is classified as vulnerable because its population has declined more than 10 percent over 10 years.

Climate change is the leading cause of decline among Galapagos kelp. El Nino , the natural weather pattern that brings unusually warm water to the Galapagos, is the leading agent of climate change in this area. Galapagos kelp is a cold-water species and does not adapt quickly to changes in water temperature. Endangered Species 1 Population reduction rate A species is classified as endangered when its population has declined between 50 and 70 percent.

A species is classified as endangered when its population has declined at least 70 percent and the cause of the decline is known.

A species is also classified as endangered when its population has declined at least 50 percent and the cause of the decline is not known.

When a species population declines by at least 20 percent within five years or two generations, it is also classified as endangered. Endangered Species: Siberian Sturgeon The Siberian sturgeon Acipenser baerii is a large fish found in rivers and lakes throughout the Siberian region of Russia. The Siberian sturgeon is a benthic species. Benthic species live at the bottom of a body of water. The Siberian sturgeon is an endangered species because its total population has declined between 50 and 80 percent during the past 60 years three generations of sturgeon.

Overfishing, poach ing, and dam construction have caused this decline. It is an endangered species because it has a very small population. The bird is only found on a single island, meaning both its extent of occurrence and area of occupancy are very small. The Tahiti reed-warbler is also endangered because of human activity.

The bird nests in bamboo and feeds on flowers and insects that live there. As development and invasive species such as Miconia destroy the bamboo forests, the population of Tahiti reed-warblers continues to shrink. Ebony is an endangered species because many biologists calculate its probability of extinction in the wild is at least 20 percent within five generations. Ebony is threatened due to overharvest ing.

Ebony trees produce a very heavy, dark wood. When polished, ebony can be mistaken for black marble or other stone. For centuries, ebony trees have been harvested for furniture and sculptural uses such as chess pieces. Most ebony, however, is harvested to make musical instruments such as piano key s and the fingerboard s of stringed instruments.

A species is classified as critically endangered when its population has declined at least 90 percent and the cause of the decline is known. A species is also classified as endangered when its population has declined at least 80 percent and the cause of the decline is not known.

A species is also classified as critically endangered when the number of mature individuals declines by at least 25 percent within three years or one generation, whichever is longer. It is critically endangered because its extent of occurrence is less than square kilometers 39 square miles. The major threat to this species is loss of its cloud forest habitat. People are clearing forests to create cattle pasture s. The Transcaucasian racerunner is a critically endangered species because of a huge population decline, estimated at more than 80 percent during the past 10 years.

Threats to this species include the salination , or increased saltiness, of soil. Fertilizers used for agricultural development seep into the soil, increasing its saltiness.

Racerunners live in and among the rocks and soil, and cannot adapt to the increased salt in their food and shelter. The racerunner is also losing habitat as people create trash dumps on their area of occupancy. Critically Endangered Species: White Ferula Mushroom The white ferula mushroom Pleurotus nebrodensis is a critically endangered species of fungus. The mushroom is critically endangered because its extent of occurrence is less than square kilometers 39 square miles. It is only found in the northern part of the Italian island of Sicily, in the Mediterranean Sea.

The leading threats to white ferula mushrooms are loss of habitat and overharvesting. White ferula mushrooms are a gourmet food item. Farmers and amateur mushroom hunters harvest the fungus for food and profit. Extinct In The Wild A species is extinct in the wild when it only survives in cultivation plants , in captivity animals , or as a population well outside its established range.

A species may be listed as extinct in the wild only after years of surveys have failed to record an individual in its native or expected habitat. Extinct in the Wild: Scimitar-horned Oryx The scimitar-horned oryx Oryx dammah is a species of antelope with long horns. Its range extends across northern Africa. The scimitar-horned oryx is listed as extinct in the wild because the last confirmed sighting of one was in Captive herds are now kept in protected areas of Tunisia, Senegal, and Morocco.

Scimitar-horned oryxes are also found in many zoos. Extinct in the Wild: Black Soft-shell Turtle The black soft-shell turtle Nilssonia nigricans is a freshwater turtle that exists only in one man-made pond, at the Baizid Bostami Shrine near Chittagong, Bangladesh. The to turtles that live at the pond rely entirely on humans for food. Until , black soft-shell turtles lived throughout the wetland s of the Brahmaputra River, feeding mostly on freshwater fish.

Unlike other animals that are extinct in the wild, black soft-shell turtles are not found in many zoos. The reptiles are considered to be the descendants of people who were miraculously turned into turtles by a saint during the 13th century. Extinct in the Wild: Mt. Kaala Cyanea The Mt. Kaala cyanea Cyanea superba is a large, flowering tree native to the island of Oahu, in the U. 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 this has contributed to the bald eagle being removed from the endangered and threatened species lists needed for the species' survival -- from sunlight and wind to food and shelter.

People can also endanger plants and animals by moving, or 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. These introduced species are called invasive species.

For example, when some fish are introduced into a lake or stream, they may prey upon, or eat the food of the native fish. The native species may then have to find a new source of food or a new home, or face becoming endangered or extinct.

Another way that people harm animals and plants is by taking them from the wild. Some people might catch an insect like the Mission blue butterfly for a butterfly collection. Others might capture a wild animal for a pet, or pick a flower because it's pretty. In addition, some people illegally hunt animals for food, skins, or fur.

In the past, lots of American crocodiles were killed so that their skins could be made into shoes and other clothing. This crocodile is now an endangered species. Can you imagine walking in the woods without hearing birds singing, or picture what a field would be like without wildflowers blooming?

Our plants and wildlife. More importantly, all living species, including people, depend on other species for survival. For example, if a fish such as the shortnose sturgeon becomes extinct, all of the species that rely on it will also suffer and may become threatened or endangered. We all depend upon plants and wildlife. From studying them, we have learned new ways of growing food, making clothing, and building houses.

Scientists have discovered how to use certain plants and animals as medicine. If we fail to protect threatened or endangered species, we will never know how they might have improved our lives.