Humans: An Endangered Species
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The Earth may be entering its sixth mass extinction: an era in which the planet's environments change so much that most animal and plant species die out. The International Union for the Conservation of Nature predicts that The five other times a mass extinction has occurred over the past million years, natural disasters were to blame. But now, human activity is killing mammal species.
In a study published Monday in the journal PNAS , scientists from Aarhus University in Denmark calculated how fast extinctions are happening, and how long it would take for evolution to bring Earth back to the level of biodiversity it currently has.
The scientists concluded that in a best-case scenario, nature will need million years to get back to the level of biodiversity we have on Earth today. Returning to the state Earth's animal kingdom was in before modern humans evolved would take million years. Evolution is the planet's defense mechanism against the loss of biodiversity. As habitats and climates change, species that can't survive die, and new species slowly emerge.
But it takes a long time for new species to fill the gaps — and that process is far slower than the rate at which humans are causing mammals to go extinct. For their calculations, the Aarhus University researchers used a database containing existing mammal species and mammals that already went extinct as humans spread across the planet. They combined that data with information about extinctions expected to come in the next 50 years, and used advanced simulations of evolution to predict how long recovery would take.
Their estimates are based on an optimistic assumption that people will eventually stop ruining habitats and causing species to die out, and the extinction rate will go back down. But even in that best-case scenario, the timeline depends on how quickly mammals start recovering. If the extinction rate doesn't start falling for another years, more species will likely disappear, causing greater diversity loss, the study said. Litopterns, like this one discovered by Charles Darwin, were a strange-looking group of prehistoric South American mammals that were not closely related to any species alive today.
When they went extinct at the end of the Ice Age, the mammal Tree of Life lost one of its deepest branches. Robert Bruce Horsfall via Wikimedia Commons. The researchers noted that in their model, certain species were given more importance than others. Matt Davis, a paleontologist at Aarhus University who led the study, cited the shrew as an example. There are hundreds of species of shrew, so if one or two go extinct, that would not kill off all shrews on Earth.
Lange's metalmark butterfly : Many endangered species are endemics, meaning they naturally have very small ranges and populations sizes, and usually require very particular soil, vegetation or climate conditions to survive.
These species are especially vulnerable to human encroachment. Among them is Lange's metalmark butterfly, protected as endangered in This unique ecosystem harbored many unique species, and many species have gone extinct as its dunes were hauled away in massive increments. After the fires, the city of San Francisco was rebuilt using brick-building material removed from the dunes. Lange's metalmark is one of the most endangered species in the United States. It declined from some , in historic times to just in It improved a bit, but then declined to just 45 butterflies in Today the species is still on the knife edge of extinction, with about individuals remaining.
Mississippi gopher frog : The Mississippi gopher frog lives in stump holes and burrows dug by other animals, laying its eggs in ponds so shallow they dry up for several months of the year, keeping them free of fish that would eat frog eggs.
It was placed on the endangered species list in The U. Fish and Wildlife Service proposed to designate 7, acres as protected critical habitat for the Mississippi gopher frog in Mississippi and Louisiana in Reduced to approximately individuals in the wild, the Mississippi gopher frog exists in just three small ponds just outside the proposed town of Tradition, Mississippi. Planned development would have a devastating effect on this rare frog. White River spinedace : The human population of Nevada grew by 35 percent between and , nearly four times faster than the national average.
Las Vegas was one of the fastest-growing areas of the state. But the city is in the middle of a desert, so accommodating that explosive growth requires securing more water from nonlocal supplies. The Southern Nevada Water Authority has proposed a massive project to pump billions of gallons of groundwater a year from eastern Nevada and western Utah through a mile pipeline to supply rapidly growing urban areas like Las Vegas.
The project will have a disastrous effect on dozens of imperiled species, including the White River spinedace, which was protected as an endangered species in One population of this rare fish was extirpated in because of irrigation diversion, and fewer than 50 fish remained in a single population in northeast Nevada. Polar bear : A polar bear is fit to swim miles for food, in search of mates or, more recently, just some ice to stand on.
With five inches of blubber keeping this enormous bear prepared for subzero temperatures, the largest member of the bear family has adapted to remarkable Arctic conditions. The fat stored in a polar bear carcass becomes essential food for other Arctic species, like the Arctic fox.
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However, the extreme impacts that human-caused climate change has had on the Arctic is pushing the polar bear closer to extinction. The rapid growth of the global human population — which has doubled since — has fed a massive push for more and more polluting fossil fuels and dramatically altered the planet's atmosphere.
A study on the relationship between population growth and global warming found that the carbon legacy of just one person can produce 20 times more greenhouse gases than one person saves by carbon-reducing steps such as driving high-mileage, using energy-efficient applicants and light bulbs. Few animals are bearing more of the brunt of the global climate crisis than the polar bear.
Humans Fit All Of The Government Criteria For 'Endangered Species' - Business Insider
Gulf sturgeon : Lake Lanier, a manmade reservoir in Georgia, feeds several important river systems in the southeastern United States and has been the site of a longstanding conflict between Georgia, Florida and Alabama over water-use rights. The gulf sturgeon, an anadromous fish, was placed on the threatened species list in Its most imperiled populations occur in the Apalachicola River, fed by rivers from Lake Lanier.
Gulf sturgeon lay eggs on the waterlines along the banks of rivers, and maintaining the right level of water is critical to their breeding success. Population growth has strained the capacity of Lake Lanier to supply water to Atlanta and other urban areas. A study explicitly identified explosive population growth as the cause of the ensuing water war between Georgia, Alabama and Florida following a regionwide drought: Nineteenth-century droughts, which are perhaps better thought of as a single multi-decadal dry period, are well within the range of historical records and could potentially have had an agricultural effect but probably would not have had an effect on water availability for people given the generally wet climate of the Southwest and the much smaller population then as opposed to now.
San Joaquin kit fox : The San Joaquin kit fox was relatively common until the s, when people began to convert grasslands to farms, orchards and cities. By , 50 percent of its habitat in California's Central Valley had been lost, due to extensive land conversions for agriculture, intensive land uses and pesticides. By , less than 7 percent of the San Joaquin Valley's original wildlands south of Stanislaus County remained untilled and undeveloped. The kit fox was listed as endangered in Today there are fewer than 7, scattered among fragmented populations.
The four counties with known San Joaquin kit foxes have grown by 60 percent — by another 1.
Besides habitat loss, the San Joaquin kit fox is threatened by pesticides and rodenticides associated with intensive agricultural use, industrial activities and residential areas in the Central Valley.