The science behind extinction
A collection of research and insights from Stanford experts who are deciphering the mysteries and mechanisms of extinction and survival in Earth’s deep past and painting an increasingly detailed picture of life now at the brink.
An estimated 8 million animal and plant species live on planet Earth. But extinction rates are accelerating. Gorillas, gazelles, frogs, rhinos and whales are among the species now critically endangered, and human activities present the biggest threat.
In mass extinctions, a huge portion of the planet’s species die off over thousands or even millions of years – a geological blink. Scientists have identified five of these events in fossil data going back roughly half a billion years.
Scientists who study past extinction events can find clues about not only the evolution of life on Earth, but also about the effects of extreme changes in our planet’s atmosphere, and how life finds ways to rebound. Stanford scientists and colleagues have uncovered evidence, for example, that the biggest extinction in Earth's history was caused by global warming that left ocean animals unable to breathe.
Other research, coauthored by Stanford geophysicist Sonia Tikoo-Schantz, suggests the crater from the giant asteroid impact linked to the dinosaur extinction some 66 million years ago may have provided niches for life.
“The fossil record is our only archive of past extinction events,” Stanford paleobiologist Jonathan Payne has said. It allows researchers to examine directly which biological traits tend to lead to higher extinction risk under different circumstances, whether in the wake of an asteroid impact or volcanic eruption, or amid global warming.
Many scientists say a sixth mass extinction is now under way. In 2019, following a review of thousands of scientific and government sources, the United Nations’ Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services reported that approximately 1 million animal and plant species are threatened with extinction. According to the report, more than 40 percent of amphibian species, nearly 33 percent of sharks, shark relatives and reef-forming corals, and upwards of 33 percent of all marine mammals are threatened.
Even parasites are under threat. Up to one-third of the world’s parasite species could go extinct within a few decades – potentially opening new niches for other, invasive parasites to exploit. And losses can snowball. As Stanford biologist Paul Ehrlich and colleagues wrote in a recent study suggesting the extinction rate is likely much higher than previously thought, “Extinction breeds extinction.”
When species vanish, benefits to humanity can be lost, too – from economic opportunities related to ecotourism to keeping in check populations of species that can spread infectious disease. The UN report estimated that as much as $577 billion in annual global crops are now at risk from loss of pollinators. The consequences do not fall equally across society. The areas projected to see some of the worst negative effects from biodiversity loss and related changes to ecosystem functions are also home to many of the globe’s poorest communities as well as large concentrations of Indigenous peoples.
This collection covers how scientists are deciphering the mysteries and mechanisms of extinction and survival in Earth’s deep past and painting an increasingly detailed picture of life now at the brink.
Scroll down for extinction research news and insights spanning the future of our own species; the disappearance of our hominid relatives and why the Neanderthals' fate could have been ours; expanding knowledge of past extinctions; the root causes and ripple effects of the Earth's ongoing biodiversity crisis; and connections between extinctions and pandemics.
Last updated: April 29, 2021
What's likely to cause human extinction – and how can we avoid it?
Stanford epidemiologist Stephen Luby sees three potential outcomes for humanity by 2100: extinction, the collapse of civilization with limited survival, or a thriving society.
Teaching 'Preventing Human Extinction' course amidst COVID-19
Teaching students about the existential threat of a pandemic as they are living through one can help make the danger feel less hypothetical and much more real.
Scientists link Neanderthal extinction to human diseases
Complex disease transmission patterns could explain why it took tens of thousands of years after first contact for our ancestors to replace Neanderthals throughout Europe and Asia.
What caused Earth's biggest mass extinction?
Scientists have debated until now what made Earth's oceans so inhospitable to life that some 96 percent of marine species died off at the end of the Permian period. New research shows the "Great Dying" was caused by global warming that left ocean animals unable to breathe.
The planet has seen sudden warming before. It wiped out almost everything.
In some ways, the planet's worst mass extinction — 250 million years ago, at the end of the Permian Period — may parallel climate change today, according to research co-authored by Stanford scientists Jonathan Payne and Erik Sperling.
When a killer climate catastrophe struck the world's oceans
“Among the slew of Very Bad Things implicated in the worst calamity the Earth has ever known, it was the global-warming-driven ocean anoxia that stands out as the primary agent of Armageddon. And in this reaper of the Paleozoic," study authors including Jonathan Payne and Erik Sperling, "see a future menace.”
Ancient die-off greater than the dinosaur extinction
When significant oxygen entered the atmosphere, ancient life multiplied. But after a few hundred million years, Earth’s oxygen plummeted, resulting in a die-off likely greater than the extinction of the dinosaurs.
Almost all life on Earth was wiped out 2 billion years ago
The most catastrophic wipe-out on Earth didn’t happen to the dinosaurs. A study co-led by Malcom Hodgskiss, a PhD student in Geological Sciences at Stanford, found extreme changes in the atmosphere killed almost 100 percent of life on Earth about 2 billion years ago.
How did marine animals become so diverse?
Upending an evolutionary theory proposed in the 1950s, scientists have found that the groups most resistant to extinction also contain the greatest ecological diversity – their members perform a larger number of different functions in ecosystems.
Brain size might put mammals at extinction risk
Scientists have long associated larger brain size with a cognitive ability to adapt to difficult scenarios, but new research suggests that mammals with relatively larger brains might be at a higher risk of extinction.
‘Tipping point for planet Earth’
Paleoecologists Anthony Barnosky and Elizabeth Hadly warn in their book, “Tipping Point for Planet Earth: How Close Are We to the Edge?,” that “changes on Earth are aggregating in a way and at a speed that indicate a planetary tipping point is just ahead. The primary driver is overpopulation and attendant overconsumption of resources.”
Study details ‘one-two punch’ of climate and land use changes on certain species
Research co-authored by Luke Frishkoff, Gretchen Daily and Elizabeth Hadly shows the effects of deforestation and climate change are amplified in a way that pushes particularly vulnerable rainforest species towards extinction, while dry-climate species persist.
As big animals go extinct, so do the benefits they offer humans
What will the world look like as iconic wild animals such as rhinos and tigers go extinct? Among other impacts: diminished biological diversity, fewer ecotourism job opportunities and the loss of benefits science is only beginning to discover, according to a call to action issued by a team of international scientists, including Stanford biologist Rodolfo Dirzo.
Larger marine animals at higher risk of extinction, and humans are to blame
In today’s oceans, larger-bodied marine animals are more likely to become extinct than smaller creatures, according to a Stanford-led report. It’s a pattern that is unprecedented in the history of life on Earth, and one that is likely driven by human fishing.
Poor outlook for biodiversity in Antarctica
An international study co-authored by Cassandra Brooks, PhD '17, has debunked the popular view that Antarctica and the Southern Ocean are in a much better environmental shape than the rest of the world.
When did humans start influencing biodiversity? Earlier than we thought
Fossil study finds early human activity — not climate shifts — led to the systematic decline of large animals around the globe that predated human migration out of Africa. The findings add to concerns about continued biodiversity loss and the impact on ecosystems.
Climate change, overharvesting may doom a pricey parasite
Stanford researchers show how warmer winters and booming demand for one of the world’s most expensive medicinal species may hurt ecosystems and communities in the Himalayas.
Three billion North American birds have vanished since 1970
North America's birds are disappearing from the skies at a rate that's shocking even to ornithologists. Yet Stanford ecologist Paul Ehrlich sees some hope in this new jolt of bad news: "It might stir needed action in light of the public interest in our feathered friends."
This is what will happen after the last fish in the ocean dies
The devastation of the vast majority of the world’s marine life is much closer than we think. According to Stanford paleobiologist Jonathan Payne, a scenario where all the ocean’s fish, mammals, and other creatures – even tiny animals like krill – are all gone is far from science fiction.
Loss of land-based vertebrates is accelerating
Analysis of thousands of vertebrate species reveals that extinction rates are likely much faster than previously thought. The researchers call for immediate global action, such as a ban on the wildlife trade, to slow the sixth mass extinction.
Deforestation and extinctions make pandemics more likely
As humans diminish biodiversity, they’re increasing the risk of disease pandemics such as COVID-19. While some species are going extinct, those that tend to survive and thrive are more likely to host potentially dangerous pathogens that can make the jump to humans.
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Zombie forests
Researchers created maps showing where warmer weather has left trees in conditions that don’t suit them, making them more prone to being replaced by other species. The findings could help inform long-term wildfire and ecosystem management in these “zombie forests.” (Source: Stanford News)
