Why does species become extinct

Without them, the elk and deer they had preyed upon thrived, and their grazing decimated streamside willows and aspens, which had provided habitat for songbirds. This left the stream banks susceptible to erosion, and a decline in songbirds allowed mosquitoes and other insects the birds would have eaten to multiply.

When the wolves were reintroduced to the park in , they once again preyed on the elk; plant life returned to the stream banks and along with it, birds, beavers, fish and other animals. Note: David Bernhardt, acting secretary of the Department of the Interior, just announced a proposal to strip gray wolves of their endangered status in the Lower 48 states.

Kelp forests are another classic example. They play an important role in coastal ecosystems because they provide habitat for other species, protect the coastline from storm surges and absorb carbon dioxide.

Otter in a kelp field. Photo: Doug Knuth. Yet kelp forests are rapidly getting mowed down by exploding numbers of purple sea urchin. California sea otters eat the purple sea urchins that feed on giant kelp. These otters used to number in the hundreds of thousands to millions, but their population has been reduced to about 3, as a result of unchecked hunting in the 19th century and pollution. Moreover, in the sunflower starfish, which also eats purple sea urchins, began dying because of a virus that was likely exacerbated by warmer waters.

Without the sea otter and the sunflower starfish predators, the purple sea urchin began feasting on the kelp forests, which declined 93 percent between and A new study found that kelp forests are now also threatened by ocean heat waves. Fish that need the kelp forests for spawning, such as sculpin, rock cod and red snapper may become vulnerable in the future as well. And Guam is covered in spiders because the birds are not there to eat them.

These large species are more vulnerable because they live longer, reproduce more slowly, have small populations, and need more food and a greater habitat area. Scientists say their loss has played a role in pandemics, fires, the decline of valued species and the rise of invasive ones, the reduction of ecosystem services, and decreased carbon sequestration.

Elephants are an apex species that may go extinct in our lifetime, as a result of tourism, habitat loss and poaching for ivory. This could dramatically change ecosystems in Africa and Asia. Through consumption and digestion, elephants disperse more seeds farther than any other animals; this fosters the growth of plants and trees that birds, bats and other animals depend upon for food and shelter. Photo: Johnny and Rebecca.

Elephants also dig water holes that all animals share, and they fertilize the soil with their rich dung, which provides food for other animals. The loss of apex species can also affect wildfires.

After rinderpest, an infectious virus, wiped out many plant-eating wildebeest and buffalo in East Africa in the late s, plants flourished. During the dry season, this over-abundance of vegetation spurred an increase in wildfires.

In the s, after rinderpest was eliminated through vaccinations, the wildebeest and buffalo returned. The ecosystem went from shrubbery to grasslands again, decreasing the amount of combustible vegetation, and the wildfires decreased. The loss of pollinators could result in a decrease in seed and fruit production, leading ultimately to the extinction of many important plants.

Flying foxes, also known as fruit bats, are the only pollinators of some rainforest plants. They have been over-hunted in tropical forests with several species going extinct. One study noted that plant species, including eucalyptus and agave, rely on flying foxes to reproduce; in turn, these plants were responsible for producing valuable products.

Bees pollinate over , species of plants, including most of the 87 crops that humans rely on for food, such as almonds, apples and cucumbers. Over the last 20 years in the U. The rusty-patched bumble bee, another important pollinator and the first bee species to be put on the endangered list, now only occupies one percent of its former range. Insect populations overall are declining due to climate change, habitat degradation, herbicides and pesticides.

A review of insect studies found that most monitored species had decreased by about 45 percent. And a German study found 75 percent fewer flying insects after just 27 years. As insect populations are reduced, the small animals, fish and birds that rely on them for food are being affected, and eventually the predators of fish and birds will feel the impacts as well.

These pests have no natural predators in their new environment so they can spread very fast and destroy the balance of their habitat. Our exploding population is another main driver of species extinction.

The causes listed above are compounded thousands of times by our ever growing number. We are competing for space, over-utilizing and our insatiable need are just overwhelming the other living things living on our planet. We are in the middle of a 6 th Extinction known as the Holocene Extinction. Conservationists are doing what they can through carefully planned breeding programs.

Governments are helping by banning illegal fishing practices and poaching. You can also help. We can leave the big tasks to the scientists, but you can make a difference in a big way. We are not totally helpless. We can co-exist. Read more stories on our environment and what you can do to help at The World Counts: Stories. Spread the message. Make a donation. Or update your wardrobe with clothes from our modest but growing selection of sustainably sourced and crafted clothes.

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Measure content performance. Develop and improve products. List of Partners vendors. Share Flipboard Email. Bob Strauss. Science Writer. Updated October 24, Featured Video. Cite this Article Format. Strauss, Bob. Prehistoric Life During the Pleistocene Epoch. The Permian-Triassic Extinction Event. Your Privacy Rights. To change or withdraw your consent choices for ThoughtCo.