In Chicago’s Field Museum, behind a series of access-controlled doors, are approximately 1,500 dinosaur fossil specimens. Paleobiologist Jasmina Wiemann walks straight past the bleached leg bones – some as big as silk – and doesn’t even look at the completely intact spinal cord, stained red by iron oxides that fill the spaces where there was once organic matter. She only has eyes for the deep chocolate brown fossils: these are the ones that contain preserved organic material – bones that offer unprecedented insights into creatures that went extinct millions of years ago.
Wiemann is part of the burgeoning field of conservation paleobiology, where researchers look to the deep past to predict future extinction vulnerability. At a time when people are about to witness a sixth mass extinctionstudying the fossil record is particularly useful for understanding how the natural world responded to problems before we arrived: how life on Earth responded to environmental change over time, how species adapted to planetary-scale temperature changes, or what to to be expected when ocean geochemical cycles change.
“It’s not something we can simulate in the lab or meaningfully observe right now,” says Wiemann. “We have to rely on the longest running experiment.”
To observe that the planetary scale experiment, scientists have developed new methods to collect information from the bones of the distant past. After Wiemann collects her fossils, she places them under a microscope that fires a laser at the specimen. She displays a section on her computer screen, 50 times its original size, and moves over the fossil’s surface until she finds a dark spot with a seemingly velvety surface – this is the fossilized organic matter.
Wiemann turns off the room lights, a small dot of light shines on the fossil, and a curved line begins to appear on the computer screen. Each compound responds differently to the laser, and where the bumps appear in this line on her graph indicates that she was successful in finding organic substances. “It’s beautiful,” she says. She would have to look through the data later, but it should show whether the sample under her microscope was warm or cold-blooded.
Using this method, Wiemann studied when hot-bloodedness emerged around the Permian-Triassic mass extinction (the largest in history) and the Cretaceous-Paleogene (when the dinosaurs became extinct). Warm-bloodedness has already been established as a factor that has made species less likely to go extinct, as they can regulate their internal temperature in changing climates. But Wiemann found a new result – that many animals evolved warm-bloodedness independently after each of these extinctions. This could have implications for how animals adapt and find resilience as the planet warms.
“If we want to make meaningful predictions in any way, even in the short term, we need to demonstrate that we understand these processes,” she says.
ohone of the first people to write about combining ecological and paleontological approaches to predict extinction vulnerability was Michael McKinney, now the director of environmental studies at the University of Tennessee. After graduating with a degree in paleontology, he began working, but says he constantly felt a need to be more relevant. “I love the dinosaurs, the big picture,” he says. “But I kept thinking that it gave us a good context, but it didn’t teach me a lot that I could apply directly to the immediate problems.”
McKinney went on to create his current department, which merges geology and ecology. Now he sees paleobiology as useful for predicting what will happen. But understanding what to do about it is more difficult.
“If you think about what the world will be like 1,000 years from now, I think time can help us answer that question,” he says. “But if I’m worried about the Amazon rainforest disappearing in the next 20 years, I’m skeptical that time can tell.”
Humans, he says, have found new ways to drive species to extinction, from the passenger pigeon to the dodo. “We work by rules that don’t really apply to the past. The things we do are so fast and so unpredictable.”
But deep time can provide insights into how species respond to very large, systemic changes — like the temperature shifts we’re seeing now. Erin Saupe, a professor of paleobiology at the University of Oxford, uses large data sets to look at patterns of extinction in the fossil record to see which traits make species most vulnerable.
In a recent paper published in Science, she and her co-authors asked whether intrinsic traits, including body size and geographic range size, are more or less important in predicting extinction than external factors such as climate change. “No one had looked at this question before,” says Saupe. Previous research has shown that larger animals are generally less likely to go extinct in marine environments but are more likely to go extinct on land, and larger “range sizes” — the distance a species is spread over — help species avoid extinction. avoid.
The team accessed a digital database to look at 290,000 marine invertebrate fossils from the past 485 million years, and used models to reconstruct the climate over that period. They found that geographic range size was the most important predictor of extinction, perhaps because of its interconnection with other factors associated with lower extinction risk. A large range size suggests that the animal is also good at moving greater distances, and if a species is widespread, a local climate change in one area is unlikely to affect all populations. The team found that all intrinsic traits they looked at, as well as climate change, were important in predicting extinction.
“Even if a species has traits that normally make them resistant to climate change and extinction, if the magnitude of climate change is large enough, they will still go extinct,” says Saupe. “I think it’s quite an important message for the current day.”
When it comes to a possible future extinction of as yet unknown degree, Saupe says the Earth has advantages it didn’t have before. For one, we no longer live on one supercontinent, which means the climate regulates better and prevents the continental interior from getting so hot and dry. However, similar to McKinney, she is concerned that resources are limited and that humans are having a disproportionate effect on biodiversity.
“In the past, when you had these big climate changes, even though they were devastating to biodiversity … species had the time, they had the resources for species to eventually recover,” she says. “Today we are concerned that those climate changes will continue, but there is no room – there are more limited resources for species to cope with those changes.”
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