by In Chicago’s Field Museum, behind a series of access-controlled doors, there are about 1,500 dinosaur fossil specimens. Paleobiologist Jasmina Wiemann walks right past the bleached leg bones – some as big as her – and doesn’t look at the perfectly intact spinal cord, stained red by iron oxides filling the spaces where organic matter once was. She only has eyes for the deep chocolate brown fossils: these are the ones with preserved organic matter – bones that provide unprecedented insight into creatures that went extinct millions of years ago.
Wiemann is part of the growing field of conservation paleobiology, where researchers look to the past to predict future extinction vulnerability. At a time when humans may be on the verge of witnessing a sixth mass extinction, studying the fossil record is very useful to understand how the natural world responded to problems before our arrival: as how life on earth has responded to environmental change over time, how species have adapted to the planet. -scale of temperature changes, or what to expect when ocean geochemical cycles change.
“This is not something we can simulate in the lab or meaningfully observe today,” says Wiemann. “We have to rely on the longest continuous experiment.”
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To observe this experiment on a planetary scale, scientists have developed new methods to gather information from the bones of the distant past. After collecting her fossils, Wiemann puts them under a microscope that fires a laser at the specimen. She displays a piece on her computer screen, 50 times its original size, and moves across the surface of the fossil until she finds a dark spot with a velvety surface – this is the fossil’s organic matter.
Wiemann turns on the lights in the room, a tiny dot of light beams on the fossil, and a curved line begins to appear on the computer screen. Each compound reacts differently to the laser, and where the bumps in this line appear across her chart it suggests that she has successfully found organics. “This is beautiful,” she says. She would have to go through the details later, but this should show whether the specimen under her microscope was warm- or cold-blooded.
If you think about what the world will be like 1,000 years from now, I think deep time can help us answer that question.
Michael McKinney
Using this method, Wiemann studied when warm blood emerged around the Permian-Triassic mass extinction (the largest in history) and the Cretaceous-Paleogene (when the dinosaurs went extinct ). Warm blood was already established as a factor that makes species less likely to go extinct, as they can regulate their internal temperature in changing climates. But Wiemann found a new result – that many warm-blooded animals evolved independently after each of the extinctions. This could have implications for how animals adapt and find resilience as the planet warms.
“If we want, in any way, even in the short term, to make sensible predictions, we need to demonstrate that we understand these processes,” she says.
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Michael McKinney, now director of environmental studies at the University of Tennessee, was one of the first to write about combining ecological and paleontological approaches to predict extinction vulnerability. After graduating with a degree in palaeontology he started working but says he always felt the need to be more relevant. “I love the dinosaurs, the big picture,” he says. “But I kept thinking that it gives us great context, but it didn’t teach me much that I could apply directly to the immediate problems.”
McKinney went on to create his current department, merging it with geology and ecology. Now, he sees paleobiology as useful for predicting what will happen. But it’s harder to understand what to do about it.
“If you think about what the world will be like 1,000 years from now, I think deep time will help us answer that question,” he says. “But if I’m worried about the fact that the Amazon rainforest is disappearing in the next 20 years, I doubt I could express that.”
Humans have found new ways, he says, to drive species to extinction, from the passenger to the dodo. “We operate according to rules that don’t really belong in the past. The things we do are so fast and unpredictable.”
But the passage of time can provide insights into how species respond to very large systematic changes – such as the temperature changes we are seeing now. Erin Saupe, professor of palaeobiology at the University of Oxford, uses large datasets to look at extinction patterns in the fossil record to see which traits are most vulnerable to species.
In a paper recently published in Science, she and her co-authors asked whether intrinsic traits, including body size and geographic range size, were more or less important in predicting extinction than extrinsic factors such as climate change. “No one has looked at this question before,” says Saupe. Previous research has shown that large animals are less likely to go extinct in marine environments but more likely to go extinct on land, with larger “range sizes” – the distance they spread species – to help avoid species extinction.
The team accessed a digital database to look at 290,000 marine invertebrate fossils from the past 485m years, and used models to reconstruct the climate over that period. They found that geographic range size was the most important predictor of extinction, possibly 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 larger distances, and if a species is widely distributed, regional climate change in one area is unlikely to affect all populations. The team found that all the intrinsic traits they looked at, as well as climate change, were important in predicting extinction.
Related: ‘Small but mighty’: the central role of invertebrates in shaping our world
“Even if a species has traits that make it resistant to climate change and extinction normally, if the magnitude of climate change is large enough, they will still go extinct,” says Saupe. “I think it’s a very important message for today.”
When it comes to facing possible extinction in the as-yet-unknown future, Saupe says Earth has advantages it didn’t have before. For one, we no longer live on a single supercontinent, which means that the climate is better regulated and prevents the continental interior from being as hot and dry. However, like McKinney, she worries that resources are limited and that people have a disproportionate impact on biodiversity.
“In the past, when you had these big climate changes, even though it was devastating to biodiversity … species had the time, they had the resources to eventually rebound,” she says. “Today, we are worried 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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