The golden lion tamarin, an almost extinct species, lives in the Atlantic Forest of Brazil, thousands of kilometers from the Amazon
According to a study that analyzed 500 years of data, extinction rates are not rising precipitously, as many believe. The researchers found that species loss peaked about a century ago, has declined since then, and is not related to climate change.
Important studies conducted in recent decades suggest that our planet is going through another mass extinctionbased on the extrapolation into the future of the extinctions observed in the last 500 years, and the idea that the extinction rates are accelerate quickly.
However, a new study, led by researchers at the University of Arizona, reveals that the extinctions of species of plants, arthropods and terrestrial vertebrates recorded over the last 500 years peaked about 100 years ago — and have been declining ever since.
In the new study, the researchers also found that most of the extinctions underlying these predictions were caused primarily by invasive species on islandsand do not constitute the most important current threat, which is destruction of natural habitats.
According to the authors of , recently published in Proceedings of the Royal Society of Londonclaims of a current mass extinction may be based on weak assumptions when projecting data from past extinctions into the future, ignoring differences in the factors driving extinctions in the past, present and future.
The study, conducted by Christian Saban e John Wiensis the first to analyze rates, patterns and causes of extinctions recent in plant and animal species. In their research, the two researchers analyzed these rates specifically in 912 species of plants and animals that have become extinct over the last 500 years. In total, data from almost 2 million species were included in the analysis.
“We found that the The causes of these recent extinctions were very different of the threats that species currently face”, says Wiens at U.Arizona.
“This makes extrapolating these patterns problematic. of past extinctions into the future, because the driving factors are changing rapidly, in particular with regard to habitat loss and climate change“, adds the researcher.
According to Saban and Wiens, the most direct information about species losses comes from recent extinctions over the last five centuries. However, studies that extrapolate these patterns into the future generally assume that recent extinctions allow us to predict the current risk of extinction and are homogeneous between groups, over time and between environments.
“To our surprise, past extinctions are weak and unreliable forms of predicting the current risk that any specific group of animals or plants faces,” says Saban.
As Extinction rates varied strongly between groupsand extinctions were most frequent among molluscs, such as snails and mussels, and vertebrates, but relatively rare among plants and arthropods.
A Most extinctions occurred in species confined to isolated islandslike the Hawaiian Islands. On continents, most extinctions occurred in freshwater habitats.
Extinctions recorded in island environments were more frequently related to invasive speciesbut habitat loss was the most important cause (and current threat) in continental regions. On islands, many species appeared become extinct due to predators and competitors brought by humans, such as rats, pigs and goats.
Somewhat unexpectedly, researchers discovered that over the past 200 years there is no evidence of an increase in extinctions due to climate change.
“That doesn’t mean climate change isn’t a threat,” Wiens said. “It just means that past extinctions do not reflect current and future threats.”
Saban does not want the study “to be interpreted as a carte blanche” to suggest that human activity does not present a significant and urgent threat to many species.
“Biodiversity loss is a huge problem right nowand I think we haven’t yet seen the types of effects it could have,” he said. “But it’s important that we talk about it accurately, that our science be rigorous in the way we can detail these losses and prevent future losses.”
“Our study shows that extinction rates are not accelerating toward the present, as many claim, but peaked many decades ago“, diz Wiens.
In some groups, such as arthropods and land plants and vertebrates, extinction rates have effectively decreased over the last 100 yearsparticularly since the beginning of the 20th century, adds the researcher.
One of the reasons for declining extinction rates “is that many people are work hard to prevent species from becoming extinct. And we have evidence from other studies that investing money in conservation actually works”, concludes the researcher.
