“Extinction breeds extinctions”: How losing one species can wipe out many more

Earth is now in the midst of a massive extinction, the sixth in the history of the planet, according to scientists.

And now a new study reports that species are dying out hundreds or thousands of times faster than expected.

The researchers also found that one extinction can cause ripple effects in an ecosystem, leaving other species vulnerable to the same fate. “Extinction causes extinction,” they write in their June 1 paper Proceedings of the National Academy of Sciences.

With the accelerated rate of destruction, scientists are racing to understand these fragile pieces of life before they are gone. “This means that the chances we have of studying and saving them will be much greater than ever before in the coming decades,” said Peter Raven, co-author of the study and professor emeritus of botany at Washington University in St. Louis. , in an email.

The findings also highlight how life can interact in unexpected ways and how difficult it can be to slow down ecological destruction once it starts. “It’s similar to climate change; once it’s rolling, it becomes increasingly difficult to settle down,” said Noah Greenwald, the endangered species director of the Center for Biological Diversity, who was not involved in the study. “We don’t know what the turning points are, and that’s scary. ”

It is worth pausing to consider what “extinction” means: a species that is completely and forever lost. Each is an irreparable event, so the idea that they are not only more common, but can also lead to additional, related extinctions is surprising. And these extinctions have consequences for humanity, from the loss of critical pollinators fertilizing crops to absent predators that would curb otherwise dispersing animals.

So researchers are now looking closely at which animals are faltering at the edge of existence to see how serious the situation has become, and to find out the best way to bring them back.

Hundreds of animals are on the verge of extinction over the next two decades

There is currently tremendous biodiversity on Earth. The number of species – birds, trees, ferns, fungi, fish, insects, mammals – is greater than ever in the 4.5 billion years of this planet’s existence. But that also means there is a lot to lose.

The new study examined 29,400 terrestrial vertebrates – mice, hawks, hippos, snakes, and the like. These species from all over the world have been cataloged by the International Union for the Conservation of Nature.

Of the species surveyed, 515 species – 1.7 percent of those surveyed – were found to be on the verge of extinction, meaning fewer than 1,000 individuals survived. These species include the vaquita, the wren Clarion Island and the Sumatran rhinoceros. And half of these 515 species have less than 250 individuals left. If nothing is done to protect them, most will die out in the next 20 years.

Species on the brink of extinction include (A) the Sumatran rhinoceros (Dicerorhinus sumatrensis; image credit: Rhett A. Butler), (B) the wren Clarion (Troglodytes tanneri; image credit: Claudio Contreras Koob), (C) de Española Giant Tortoise (Chelonoidis) hoodensis; image credit: Gerardo Ceballos), and (D) the Harlequin frog (Atelopus varius; image credit: Gerardo Ceballos).
PNAS

But these abyss abysses are not evenly distributed throughout the world; they are concentrated in biodiversity hotspots such as tropical rainforests. That makes sense, because tropical forests have the most diverse species in the beginning and destroy most habitats. “About two-thirds of all species are estimated to occur in the tropics, and we know less about them than in other parts of the world,” said Raven. ‘[Y]he more than a quarter of all tropical forests have been cleared in the 27 years since the ratification of the Convention on Biological Diversity. ”

Losing an endangered species can endanger many others

The species staggering on the brink of eternal loss often live alongside other endangered species, even if they are present in greater numbers. The fringe species then serve as loud sirens to the potentially greater threat to other life in their environment. When species die in a pond, forest stand or river basin, others soon follow.

In many cases, species interact with others in complicated and often unforeseen ways that are not recognized until they are gone. For example, if a herbivorous insect dies, the plants it eats can roam and suffocate other vegetation. Meanwhile, the birds that feed on the insect may be without an important food source. Each of these subsequent changes can have countless different effects on distant species, and so on and so forth. The disturbance can continue until the ecosystem is barely recognizable.

Scientists have observed ripples like this disturbances in ecosystems decades in places like the Amazon rainforest, looking at what happened when species died out in a particular area or when a habitat broke up.

As these ecosystems deteriorate or collapse, people lose many functions from nature that they take for granted, such as forests that generate rain for aquifers or mangroves that protect the coasts from erosion. For example, many terrestrial vertebrates are critical for spreading the seeds from trees. Without them, the composition of a forest could change.

Even if a less diverse prairie, forest, or desert remained, it would be more vulnerable to shocks such as fires and severe weather. Various ecosystems act as buffers against extremes in the environment, and without them, people are more at risk of phenomena such as heat waves without vegetation to cool the air, or they can undergo more flooding without mangroves to absorb waves.

And as people move closer to areas that were once wild, they are at greater risk of exposure to threats such as animal-borne illness and wildfire. So the economic and health costs of runaway extinctions can be huge.

People are the problem and people are the solution

The new study is part of a steady stream of grim news for endangered species. In 2019, the United Nations’ Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) released a massive 1,500-page report on global biodiversity. The report concluded that up to 1 million species are threatened with extinction, including 40 percent of all amphibian species, 33 percent of corals and about 10 percent of insects.

And a connecting theme among the various extinction studies is that man is blamed.

By destroying habitats, spreading diseases, keeping livestock, dumping waste, over-harvesting, overfishing and climate change, the 7.5 billion people on this planet have become their own strength unlike any other in nature.

“We are no longer part of the global ecosystem and live in a broad, broad world,” said Raven. ‘[W]e are one species, completely dominant, among the millions of others out there. ”

True, species are becoming extinct naturally, but extinction is now thousands of times higher than the expected background percentage. It can be difficult to find out if an organism has disappeared as a direct result of human activity or because a species it depended on has been wiped out by humans, but both types of losses stem from humanity. “We can’t easily reverse the trend, but we can learn as much as possible in the time we have left,” said Raven.

The fact that human activities cause the vast majority of these extinctions means that changing human activities can help reduce vulnerable types of destruction.

The conservation policy has already proven effective in counteracting some permanent losses, such as the Endangered Species Act in the United States. It even stimulates the recovery of several species, such as the bald eagle. And there is still time to save others species that are on the edge. But to save what’s left requires concerted action and time to act is running out.

“You don’t want to get into a deep depression. You want to get involved and do the very simple things we can do to avoid destroying the planet, ”said Stuart Pimm, a professor of wildlife conservation at Duke University and president of Saving nature, a non-profit environmental conservation organization. “The important story is that we can do a lot about it.”

Since people cause most of the destruction that causes extinction, people can change their behavior to protect life. One of the most effective measures people can take to protect endangered species is to protect the environment in which they live and protect them from mining, drilling, development, and pollution.

“We can certainly make a difference. We can accelerate the extinction, “said Greenwald. “We know how to do that. We can free up more space for nature. ‘

Another tactic is to build corridors to connect fragmented ecosystems, creating larger adjacent areas. This can help grow synergy between species and build a more resilient ecosystem that can better withstand the disappearance of a species and restore deterioration.

However, the threats to so many species have been building up for years and they cannot be reversed overnight. It will take a sustained global conservation effort to protect and restore loved ones to the crowds that once swam, flew, and walked the Earth.

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