Climate Change and Marine Extinctions: Lessons from the Permian Era

Around 252 million years ago, Earth experienced its most devastating biological catastrophe. Known as the Permian-Triassic extinction or the “Great Dying,” this event wiped out approximately 96 percent of all marine species and 70 percent of terrestrial vertebrates. It remains the most severe mass extinction in our planet’s history, dwarfing even the event that eliminated the dinosaurs. What makes this ancient disaster particularly relevant today is its primary cause: rapid global warming that left ocean animals unable to breathe. Understanding this prehistoric catastrophe offers sobering lessons about our current climate trajectory and the threats facing modern marine ecosystems.

The Permian extinction: Earth’s deadliest crisis 🔗

The largest extinction in Earth’s history marked the end of the Permian period, some 252 million years ago. Long before dinosaurs, our planet was populated with plants and animals that were mostly obliterated after a series of massive volcanic eruptions in Siberia. The scientific consensus is that the main cause of the extinction was the flood basalt volcanic eruptions that created the Siberian Traps, which released sulfur dioxide and carbon dioxide, resulting in oxygen-starved, sulfurous oceans, elevated global temperatures, and acidified oceans.

Researchers at the University of Washington and Stanford University have now pieced together exactly how this disaster unfolded. The Permian mass extinction in the oceans was caused by global warming that left animals unable to breathe. As temperatures rose and the metabolism of marine animals sped up, the warmer waters could not hold enough oxygen for them to survive.

How warming oceans suffocated marine life 🔗

The mechanism behind this mass death was deadly simple. Warmer water holds less dissolved oxygen. Simultaneously, as oceans warm, marine animals’ metabolism speeds up, meaning they require more oxygen, while warmer water holds less. This created a lethal double bind where marine creatures needed more oxygen precisely when less was available.

Researchers simulated the dynamics of the ancient extinction using an Earth system model that reproduced the ocean warming and oxygen loss indicated by the geologic record. The results were stark: oceans lost about 80 percent of their oxygen. About half the oceans’ seafloor, mostly at deeper depths, became completely oxygen-free.

During the latest Permian before the extinction, global average surface temperatures were about 18.2 °C, which shot up to as much as 35 °C, this hyperthermal condition lasting as long as 500,000 years. This extreme warming fundamentally transformed ocean chemistry and made vast swaths of the seas uninhabitable.

The geographic pattern of death 🔗

One of the most revealing aspects of the Permian extinction was its geographic signature. Many species that lived in the tropics also went extinct in the model, but high-latitude species, especially those with high oxygen demands, were nearly completely wiped out. Species living near the poles suffered most severely.

Why did polar species face higher extinction rates? Since tropical organisms’ metabolisms were already adapted to fairly warm, lower-oxygen conditions, they could move away from the tropics and find the same conditions somewhere else. But if an organism was adapted for a cold, oxygen-rich environment, then those conditions ceased to exist in the shallow oceans.

Modern extinction risks: echoes of the Permian 🔗

The parallels between Permian conditions and our current situation are disturbing. The situation in the late Permian – increasing greenhouse gases in the atmosphere that create warmer temperatures on Earth – is similar to today. Current trajectories suggest we may be following a familiar and dangerous path.

Under a business-as-usual emissions scenario, by 2100 warming in the upper ocean will have approached 20 percent of warming in the late Permian, and by the year 2300 it will reach between 35 and 50 percent. While we are not yet at Permian levels, the direction of travel is concerning.

Polar species face the greatest threat 🔗

A 2024 study from the University of Oxford analyzed over 290,000 fossil records spanning 485 million years and confirmed similar vulnerability patterns today. Species occupying climatic extremes, for instance in polar regions, were disproportionately vulnerable to extinction, and animals that could only live in a narrow range of temperatures were significantly more likely to become extinct.

Global extinction risk is greater for polar species than for tropical ones, threatening higher-latitude richness. Species initially inhabiting the tropics can tolerate warm, low-oxygen waters, making them resilient to the climatic expansion of those conditions. By contrast, polar species occupy a disappearing climate niche and lack habitat refugia as the climate warms.

Polar specialists cannot migrate, making them susceptible to competition and extinction from range-extending subpolar species. The borealisation and australisation of Arctic and Antarctic ecosystems, respectively, is underway as these regions become more hospitable for the larval and adult life-history stages of lower-latitude species.

Ocean acidification compounds the threat 🔗

Modern marine species face not only warming but also ocean acidification. As the ocean absorbs excess atmospheric carbon dioxide, seawater becomes more acidic. Ocean acidification can retard development, impair skeletogenesis and result in smaller larvae. For polar marine invertebrates, which already face warming stress, acidification adds another layer of physiological challenge.

Water temperature and oxygen availability are two key factors that will change as the climate warms due to human activity. Warmer water is, itself, a risk factor for species that are adapted for cooler climates. Warm water also holds less oxygen than cooler water, and leads to more sluggish ocean circulation that reduces the oxygen supply at depth.

The emergence of invasive species 🔗

While some species face extinction, others are thriving in warming waters. Rising ocean temperatures are enabling opportunistic species to expand into new territories, often with devastating consequences for native ecosystems.

Lionfish: a model invasive species 🔗

The Indo-Pacific lionfish provides a stark example of climate-enabled invasion. Warming water temperatures due to climate change could expand the range of many native species of tropical fish, including the invasive and poisonous lionfish. First spotted off Florida’s Atlantic coast around 30 years ago, likely released from aquariums, lionfish have become poster children for marine invasive species.

Lionfish continue to expand at astonishing speeds and are harming native coral reef ecosystems in the Atlantic, Gulf of America, and Caribbean. Their impact is severe: in the Atlantic, a single lionfish on a reef can reduce the recruitment of native fish by 79 percent within just a few weeks.

What drives their success? The range of lionfish continues to expand as ocean temperatures rise. Lacking natural predators or competitors in the newly colonized waters, lionfish have proliferated nearly unchecked, causing much damage to reef ecosystems. Models predict the situation will worsen: researchers developed a model predicting an increase in the lionfish geographical distribution of 45 percent on the southeast U.S. Continental Shelf by 2100, with the implication that ocean warming would allow lionfish to invade higher latitudes.

The Mediterranean Sea now faces similar invasion pressure. The Mediterranean Sea is now experiencing an early-stage lionfish invasion, spreading westward from the eastern Mediterranean, likely through the Suez Canal. Predictions indicate significant expansion, especially in the eastern and central Mediterranean, under greater warming scenarios.

Crown-of-thorns starfish: coral’s deadliest predator 🔗

On the Great Barrier Reef, crown-of-thorns starfish are notorious for their destructive consumption of coral that decimates tropical reefs. Their populations can rapidly increase from 0-1 starfish per hectare to more than 10-1000 per hectare in short order, causing a drastic change to benthic communities.

Crown-of-thorns starfish are one of the greatest threats to the Great Barrier Reef and a leading cause of coral loss over the past 40 years. When an outbreak occurs, the starfish can strip a reef of 90 percent of living coral tissue. Climate change is intensifying this threat through multiple pathways.

Research from the University of Sydney has revealed a troubling paradox: juvenile crown-of-thorns starfish can tolerate almost three times the heat intensity that causes coral bleaching. This means that, even if the coral-eating adult stage declines in climate change-driven ocean warming scenarios, their herbivorous young can wait patiently for the opportune moment to grow into carnivores.

Climate change is increasing the frequency of marine heatwaves which cause coral bleaching. The combination of climate change and crown-of-thorns starfish outbreaks create additional concerns: starfish may eat the few corals that survive after heatwaves. By removing these corals, the starfish could prevent or slow down reef adaptation.

Jellyfish blooms intensify 🔗

Jellyfish populations are surging in many ocean regions. The explosion in their numbers has been attributed to warming seas and even increased pollution; unlike many other marine creatures, jellyfish can cope with reduced oxygen levels.

According to a massive new analysis of poisonous or venomous aquatic animals, dangerous species might become increasingly common in new ranges. Species whose ranges might shift polewards due to warmer water include lionfish, sea snakes, crown-of-thorns starfish and a number of different types of venomous jellies.

Venomous species are of particular concern. The box jellyfish, which is spreading into waters that had previously been too cool to support it, has venom that causes a severe reaction that can cause death within minutes. The deadly irukandji and box jellyfish have been responsible for increasing amounts of deaths in Australia and may be moving southwards into more populated areas as the climate warms.

Ocean warming as a result of anthropogenic climate change is thought to help some jellyfish species grow and develop more quickly than others, causing populations to expand significantly. Warming waters are also encouraging certain jellyfish species to expand their ranges, appear earlier in the season and increase in overall numbers.

The ecological disruption extends far beyond stinging swimmers. Migrating coral makes way for other marine species – including jellyfish – to extend their habitable territory. This throws the local ecosystems off-balance as jellyfish join the competition for zooplankton, as well as hinder the lives of fish by eating their eggs, larvae and juveniles.

What the Permian can teach us 🔗

The Permian extinction demonstrates that ocean warming and oxygen loss can drive extinctions on a catastrophic scale. This study highlights the potential for a mass extinction arising from a similar mechanism under anthropogenic climate change.

However, research also provides hope. Reversing greenhouse gas emissions trends would diminish extinction risks by more than 70 percent, preserving marine biodiversity accumulated over the past approximately 50 million years of evolutionary history. The study found that aggressive and rapid reductions in greenhouse gas emissions are critical for avoiding a major mass extinction of ocean species.

The fossil record teaches us that recovery from mass extinction takes millions of years. The Permian extinction was followed by prolonged periods of ecological instability before marine ecosystems could fully recover. We have the knowledge to avoid repeating this catastrophe, but the window for action is narrowing.

What do you think? Given the parallels between Permian-era warming and our current trajectory, what responsibility do we have to future generations to prevent a similar outcome? And as invasive species reshape marine ecosystems, how should coastal communities adapt to increasingly unfamiliar ocean inhabitants?

References

1. https://www.ox.ac.uk/news/2024-03-08-new-study-reveals-insight-which-animals-are-most-vulnerable-extinction-due-climate
2. https://news-oceanacidification-icc.org/2025/01/10/climate-change-and-polar-marine-invertebrates-life-history-responses-in-a-warmer-high-co2-world/
3. https://www.fisheries.noaa.gov/southeast/ecosystems/impacts-invasive-lionfish
4. https://link.springer.com/article/10.1007/s00227-024-04580-6
5. https://www.sydney.edu.au/news-opinion/news/2023/10/19/reef-devouring-predator-survives-coral-bleaching-and-feasts-on-survivors.html