Extinction threatens many species, study finds
Global population trends among 71,000 animal species show almost half are “sliding towards extinction”, some at alarming rates, a new study warns.
The researchers found that 48% of the species analyzed were in decline, while only 3% were increasing and 49% remained stable, according to the study published Tuesday in the journal “Biological Reviews”.
The disparity between the decreasing number of species and their increasing numbers shows “a rather alarming net loss of biodiversity”, said Daniel Pincheira-Donoso, co-author of the study and associate professor of evolutionary biology and macroecology at the Queen’s University Belfast. The United Kingdom.
The rapidly growing imbalance signals an impending “sixth extinction,” the authors said in the study, titled: “More Losers Than Winners: Investigating Anthropocene Defaunation Across Diverse Population Trends.”
Although species declines are concerning, Stuart Pimm, a conservation scientist for nearly 50 years who is not associated with the study, said his other findings represent good news for many species.
The study “goes beyond the simplistic view that everything is going to hell,” said Pimm, Doris Duke Professor of Conservation Ecology at Duke University. “Many species – and many important species – and are doing well, if not better.”
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What were the conclusions of the study?
Population trends were analyzed in the world’s mammals, birds, reptiles, amphibians, fish and insects. The study found that “animal populations and entire species are declining on the tree of life”.
Among his other discoveries:
- Biodiversity is increasingly threatened by habitat destruction, invasive species and other factors.
- The scale of animal decline represents “one of the most alarming consequences” of human impacts on the planet.
- The number of collapsing populations “is far greater than the adaptive ‘catching up’ of the species.”
- Population trends are unknown for many species, especially in the tropics where other species are struggling.
- Reptiles and fishes have more stable groups than some other species, but they also have a greater number of species whose population trends are unknown.
- Amphibians are experiencing some of the largest decreases in population losses, with 63% of species examined declining.
- Of the species classified by the International Union for Conservation of Nature’s Red List as “not threatened”, 33% are in decline.
“Now is a crucial time to protect the future integrity of biodiversity, and therefore the persistence of humanity,” the authors concluded.
Not all bad news
The study’s findings are “interesting and significant with mixed content”, said Pimm, in Africa studying elephants this summer.
“Some species are in big trouble, but we shouldn’t forget that we’re doing a lot with many endangered species,” he said. “There are places where things are really quite gloomy, but others where things are much better.”
“If you’re a lark, an iconic bird of the English countryside, you’re in trouble,” because of intensive farming, insecticides and herbicides, Pimm said. But successful examples can be found among southern African elephants and bald eagles, peregrine falcons and many ducks in the United States.
“A lot of things are better because we did it this way,” and the success illustrates that further progress can be made, he said. For example, he highlighted the United Nations goal of conserving 30% of the world’s land and oceans by 2030.
Why should we care about endangered species?
It’s a “global environmental disaster” that will impact our own lives sooner or later, Pincheira-Donoso said. He compared the importance of biodiversity to the engine of a car.
“An engine is made up of very large, critical pieces and very small pieces like screws, but all of those pieces are in that engine because together they make the engine work,” he said. “If you start taking little chunks of it, or certainly if you take a big chunk of it, you know your engine will fail and eventually crash.”
The same complex interaction occurs in natural ecosystems, he said. “If you start removing species from an ecosystem, it’s like removing screws from random parts of your engine, you know it’s going to crash because each species plays a role.”
Amphibians, for example, play an important role in ecosystems, but they are declining more than any other living organism, Pincheira-Donosa said.
“The amphibian extinction rate is truly alarming…more than all other vertebrates combined,” he said. “In every ecosystem where you see a massive amphibian decline, you’re basically taking a lot of random screws from your engine and it’s causing a collapse.”
What were the five mass extinctions?
Using the fossil record, scientists have uncovered five periods in Earth’s geological history in which many species died out. According to the American Museum of Natural History, the periods and extinctions were:
- Ordovician-Silurian: 440 million years. Small marine organisms.
- Devonian: 365 million years ago. Many tropical marine species.
- Permian-Triassic: 250 million years ago. A range of species, including many vertebrates.
- Triassic-Jurassic: 210 million years ago. Terrestrial vertebrate species.
- Cretaceous-Tertiary extinction: 65 million years ago. About 50% of Earth’s plants and animals.
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