Second, to the extinction rates of previous mass extinctions. The background rate of extinctions of vertebrates that we would expect is around 0. This means birds, mammals and amphibians have been going extinct to times faster than we would expect. Researchers think this might even be an underestimate.
One reason is that some modern species are understudied. Some might have gone extinct before we had the chance to identify them. This might be particularly true for species a century ago when much less resource was put into wildlife research and conservation. Another key point is that we have many species that are not far from extinction: species that are critically endangered or endangered. If they did, extinction rates would increase massively.
In another study published in Science , Michael Hoffman and colleagues estimated that 52 species of birds, mammals and amphibians move one category closer to extinction on the IUCN Red List every year.
Again, to times higher than the background rate. One way to answer this is to compare recent extinction rates with rates from previous mass extinctions.
In the chart we see the comparison of non-dinosaur vertebrate extinction rates during the K-Pg mass extinction to recent rates. This shows how many times faster species are now going extinct compared to then. We see clearly that rates since the year are estimated to be 24 to 81 times faster than the K-Pg event. If we look at even more recent rates, from onwards, this increases to up to times faster.
Again, this might even be understating the pace of current extinctions. We have many species that are threatened with extinction: there is a high probability that many of these species go extinct within the next century. Recent rates of extinction, if they continued, would put us on course for a sixth mass extinction. A final way to check the numbers on this is to estimate how long it would take for us to get there. If this number is less than 2 million years, it would qualify as a mass extinction event.
Earlier we came up with a crude estimate for this number. If these species did go extinct soon, our extinction rates would be much higher than the average over the last years. To be clear: these are not predictions of the future. The results are shown in the chart. If only our critically endangered animals went extinct in the next century, this would increase to a few thousand years. In any scenario, this would happen much faster than the million year timescale of previous mass extinctions.
This makes two points very clear. Current rates do point towards a sixth mass extinction. Second, these are scenarios of what could happen. There is one thing that sets the sixth mass extinction apart from the previous five. It can be stopped. We can stop it. There was no one or nothing to hit the brakes and turn things around. We are the primary driver of these environmental changes: deforestation, climate change, ocean acidification, hunting, and pollution of ecosystems.
But is also the best news we could hope for. It means we have the opportunity and some would argue, the responsibility to stop it. There are a number of examples of where we have been successful in preventing these extinctions [see our article on species conservation]. Or, worse, that they will accelerate. Nothing about that is inevitable. This is the first step to understanding what we can do to turn things around. This is what our work on Biodiversity aims to achieve.
The world missed all of them. Perhaps, then, the loss of biodiversity is unavoidable. Maybe there is nothing we can do to turn things around. Thankfully there are signs of hope. As we will see, conservation action might have been insufficient to meet our Aichi targets, but it did make a difference.
Tens of species were saved through these interventions. We need to make sure these stories of success are heard. In fact, the risk here is asymmetric: growth in one wildlife population does not offset a species getting pushed to extinction.
A species lost to extinction is a species lost forever. But we can make sure two messages are communicated at the same time. If there was no hope of the second one being true, what would be the point of trying? If our actions really made no difference then why would governments support anymore conservation efforts?
No, we need to be vocal about the positives as well as the negatives to make clear that progress is possible. And, importantly, understand what we did right so that we can do more of it. In this article I want to take a look at some of these positive trends, and better understand how we achieved them. For anyone interested in wildlife conservation, losing a species to extinction is a tragedy.
Conservation efforts might have saved tens of beautiful species over the last few decades. We might have missed this, but efforts have not been completely in vain. In a recent study published in Conservation Letters , researchers estimate that between 28 and 48 bird and mammal species would have gone extinct without the conservation efforts implemented when the Convention on Biological Diversity came into force in In the last decade alone from to , 9 to 18 bird, and 2 to 7 mammal extinctions were prevented.
This has preserved hundreds of millions of years of evolutionary history. It prevented the loss of million years of evolutionary history of birds, and 26 million years for mammals. What this means is that extinction rates over the last two decades would have been at least three to four times faster without conservation efforts.
This does not mean that these species are out-of-danger. In fact, the populations of some of these species is still decreasing. We see this in the chart, which shows how the populations of these bird and mammal species that were expected to have gone extinct are changing.
This is positive, but makes clear that many of these species are still in decline. Conservation has only been able to slow these losses down. The study authors suspect that the extinction rate will only increase if trends continue—possibly resulting in what scientists call the sixth mass extinction in Earth's history. Another conclusion of the study that can't be ignored, says Yale's Crane, is "that there remain huge gaps in knowledge.
At least for the most diverse groups of organisms on Earth, the urgent need to clarify how many species there are, where they live, and how their populations are changing remains a key impediment. To Jenny McGuire , a postdoctoral research scientist at the University of Washington's School of Environmental and Forest Sciences who wasn't involved in the study, the results aren't surprising. Though some might quibble about the exact rate, she says, "in general scientists are in agreement that we're at a period of heightened extinction risk and rates, and that's been occurring nearly since humans have come onto the landscape.
McGuire sees the new study as a "really excellent call to arms" for people to act to prevent more species from vanishing. She says that people can vote for policies that lessen the impact of climate change, which is hitting the oceans particularly hard by raising the water's pH and dissolving the shells of many marine animals. People can also encourage their governments to connect one nature reserve to another.
Pimm says protected areas, the "frontline of conservation," have kept extinction rates of mammals, birds, and amphibians 20 percent lower than they would have been without refuges.
Nearly 13 percent of Earth's land has been set aside, but only 2 percent of the ocean is part of a refuge. Pimm and colleagues noted that global databases and crowdsourcing are helping to fill in blanks by tracking biodiversity outside of protected areas, where species tend to be less studied.
And of course anyone can contribute by becoming a citizen scientist like Trouern-Trend, who said he's part of a "a niche of people who want to help out" by giving conservationists a snapshot of our world.
All rights reserved. Share Tweet Email. Why it's so hard to treat pain in infants. This wild African cat has adapted to life in a big city. Animals Wild Cities This wild African cat has adapted to life in a big city Caracals have learned to hunt around the urban edges of Cape Town, though the predator faces many threats, such as getting hit by cars.
One-third of the known invertebrate species are now threatened with extinction. Water pollution, water projects, and groundwater withdrawal threaten freshwater invertebrates, while deforestation and animal agriculture is also a great factor of invertebrate endangerment or extinction. In addition, reef-building corals in the ocean are diminishing at an increasing rate. Mammal Extinction Crisis Probably the most characteristic element of the current extinction crisis is that most of our primate relatives are in serious danger.
About half of all the primate species on Earth are at the brink of extinction. Marine mammals — including dolphins, whales, and porpoises — are particularly close to becoming extinct. Reptile Extinction Crisis More than one fifth of all known reptile species are considered endangered or close to becoming extinct. This has been particularly pronounced for island reptile species, counting at least 28 island reptiles having disappeared so far. This pattern of extinction, commonly seen in the islands, is finding its way toward the mainland as well.
This crisis is mainly due to human intervention causing fragmentation in the continental habitats, which results in island-like territories, isolating species among each other. Reptiles are especially threatened by non-native species that compete for resources or feed on them, and habitat loss. Plant Extinction Crisis Plants are the food we consume and the producers of the oxygen we breathe through the process of photosynthesis. We have also polluted some habitats with chemicals and refuse, making them unfit for wildlife.
These causes of extinction are known as indirect destruction. Animals may also become extinct through direct destruction. This includes the hunting and capturing of animals. Humans have always hunted and killed wildlife but early humans lived more in harmony with nature, they killed animals for essentials like food and clothing. When guns were invented mass destruction of species was possible.
Animals have been, and still are, killed for meat, clothing,medicines, feathers, eggs, trophies, tourist souvenirs - and sometimes just for amusement.
Some species are still captured in the wild for the live pet trade, even though their numbers are dwindling. The extinction of at least species of animals has been caused by humans, most of them in the 20th century. Today there are about 5, endangered animals and at least one species dies out every year. There are probably many more which become extinct without anyone knowing.
0コメント