Extinction threat may be greater than previously thought, new global study finds
The global extinction crisis underway may be more intense than previously thought as humans continue to tear up land, overuse certain resources and heat up the planet, new research led by the University of Minnesota indicates.
Nearly one in three species of all kinds — 30% — face global extinction or have been driven to extinction since the year 1500, according to the new survey published in the journal "Frontiers in Ecology and the Environment."
That's significantly higher than prevailing global estimates and the findings surprised lead author Forest Isbell, associate professor in the university's Department of Ecology, Evolution & Behavior. He said one of the reasons is that it takes more insects and other lesser-studied species groups into account.
"I honestly figured it was much lower," Isbell said. "I would have estimated it was 20%."
Prevailing global estimates have ranged from 12.5% across all species groups to 25% of the well-studied ones, such as animals and plants, he said.
Noah Greenwald, endangered species director at the nonprofit Center for Biological Diversity, called the numbers "quite alarming."
"It took many years for climate change to become a prominent household concern," Greenwald said. "The extinction crisis is really part and parcel of a similar scope and severity to climate change."
Healy Hamilton, chief scientist at the nonprofit research group NatureServe, said the numbers do not surprise her. She said her organization has demonstrated for years that about one-third of plants and animals in the United States are vulnerable to extinction or have already become extinct. The new survey's real power is the broad geographic and taxonomic coverage, she said.
"The majority of species on the planet are plants and insects and other invertebrate animals that we know so little about we cannot even determine the extent to which they are threatened," she said. "And yet those are the very species which help purify our air, filter our water, maintain the health of our soils, pollinate plants we need for food, fuel and fiber, and provide medicines to hundreds of millions of people."
The new findings are the result of a survey that elicited 3,331 responses from biodiversity experts around the world studying in nearly 200 countries. The 30% figure is the median of the middle-tier estimates respondents provided, which ranged from 16 to 50%.
Further, the study found that if trends continue, by the end of the century the imperiled share will grow to 37%, a share that could be significantly reduced if conservation efforts were immediately escalated. Overall, the respondents agreed that the loss of biological diversity is decreasing the functioning of ecosystems "and nature's contributions to people."
Scientists are working to understand biodiversity loss and its impacts and do not know exactly how many species exist on the planet. The study did not put a specific number behind the percent of species threatened or gone.
"There's huge uncertainty with these numbers," Isbell said. "The value is actually asking people for their input from everywhere."
Interestingly, female biodiversity experts from the global south provided much higher loss estimates. Forest said he thinks part of the explanation is that the women work in regions where biodiversity loss is more intense, and because men disproportionately study the less-threatened species.
He said he's not sure what the results say about the threat to species in Minnesota. But he said the state is part of a wealthy country and there is a trend in those responses, he said.
"People from wealthy countries systematically provided lower estimates for biodiversity loss in the past and more pessimistic estimates for the future," he said. Isbell said he does not know why.
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