A sixth extinction-level event, which scientists had warned is looming, is here, a paper from Stanford, Princeton, and Berkeley claims.
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An extinction-level event is a widespread decrease in the amount of life on Earth, at a pace far greater than random. Generally, it refers to life one can see, as opposed to miscrocopic life.
The paper, "Accelerated modern human-induced species losses: Entering the sixth mass extinction," says a vast range of different species are becoming extinct far more rapidly than in any time in history, based on the fossil record.
"The oft-repeated claim that Earth's biota is entering a sixth 'mass extinction' depends on clearly demonstrating that current extinction rates are far above the background rates prevailing in the five previous mass extinctions," writes the scientific team, and does exactly that.
Looking at vertebrates, the number of species that went extinct in the last 100 years would have taken as much as 800 to 10,000 years according to the background rate, based on the fossil record, says the team. That acceleration is precisely the definition of a "mass extinction event".
Previous mass extinction events are believed to have been caused by natural factors, from volcanic eruptions that disrupted planetary weather conditions to asteroid impacts. The current disaster is being driven by humanity, including through the impact of climate change, which is also being caused (this time) by man, according to the scientific consensus.
The Red List of Endangered Species, backed by governments, scientists and conservationists, grew to 22,784 species in 2015, almost a third of all animals and plants sampled, from 22,413 a year ago, the paper says.
From flowers to lions
The number of animals and plants at risk of extinction rose in 2015 despite pledges by governments to improve protection. The species under threat range from amphibians to spiders to West African lions to orchids, the study shows.
Habitat loss, for instance by cutting down forest for farmland, cities or roads, was the main cause of the rise in number of endangered species, according to the list compiled by the International Union for Conservation of Nature.
Lions in Africa retained an overall listing as "vulnerable", one of the least endangered categories, thanks to conservation in southern Africa. But lions in West Africa were listed in a more severe category as "critically endangered" due to habitat loss and a decline in prey caused by human hunting, it said. There are also "rapid declines in East Africa, historically a stronghold for lions - mainly due to human-lion conflict and prey decline," the paper adds.
Trade in lion bones and other body parts for traditional medicines were an emerging threat.
'We are not on track'
In 2011, almost 200 governments set a goal of preventing by 2020 the extinction of known species and reducing threats to those most in decline. No known species went extinct in 2015 but many came closer to the brink.
"We are not on track," said Craig Hilton-Taylor, head of the IUCN Red List Unit, told Reuters of the 2020 goals.
On the upside, there have been some conservation successes, such as the Iberian lynx, whose number rose to 156 adults in 2012 from 52 a decade earlier.
It bears noting however that the small number of individuals means that the lynx probably faces a genetic bottleneck, as the cheetah does today: inbreeding by the few survivors of a bottleneck in the past has led to poor fertility in cheetah adults and high mortality among cheetah kittens. The fact that 156 lynxes still exist does not mean the species is safe – though Prof. David Haussler of the University of California believes that futuristic genetic editing techniques could help preserve species by restoring some genetic diversity.
Meanwhile, it isn't just spotted owls or black-footed ferrets in danger. Some economically valuable species were added to the as endangered list, Hilton-Taylor said.
The list said that practically all of the 84 species of tropical Asian slipper orchid, which are prized ornamental flowers, were threatened, mainly because of over-collection and habitat loss. Nine of 17 species from the tea plant family assessed were also endangered because they are used for making tea and medicines or as ornamental plants and firewood.
"Losing these plants would reduce the genetic diversity of tea," Hilton-Taylor said. The plants might be valuable replacements for current species of drinking tea if environmental conditions were to change in future.
The new study builds on previous research that had warned of the sixth great extinction approaching like a freight train. A study a year ago, led by Stuart Pimm of Duke University, found that extinction rates were 1,000 times higher than normal due to deforestation, global climate change, as well as over-fishing.
"We are on the verge of the sixth extinction," Pimm told the press a year ago, adding: "Whether we avoid it or not will depend on our actions."
Now his peers say the verge is passed, though they too add that if action is taken immediately - at least some of the "dramatic decay in biodiversity" could be averted. Meaning, some of the species teetering on the brink could yet be saved.