UV radiation pulse played a role in a mass extinction event, fossilized pollen reveals

Published

3 years ago

January 10, 2023

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A lethal pulse of ultraviolet (UV) radiation may have played a role in Earth’s biggest mass extinction event, fossilized pollen grains reveal.

Pollen that dates to the time of the Permian-Triassic mass extinction event, roughly 250 million years ago, produced “sunscreen” compounds that shielded against harmful UV-B radiation, the analysis found. At that time, approximately 80% of all marine and terrestrial species died off.

For the study, which was published Jan. 6 in the journal Science Advances (opens in new tab) , a team of international scientists developed a new method of using a laser beam to examine the miniscule grains, which measure about half the width of a human hair and were found embedded onto rocks unearthed in southern Tibet, according to a statement.

Plants rely on photosynthesis to convert sunlight into energy, but they also need a mechanism to block out harmful UV-B radiation.

“As UV-B is bad for us, it’s equally as bad for plants,” Barry Lomax (opens in new tab) , the study’s co-author and a professor in plant paleobiology at the University of Nottingham in the U.K., told Live Science. “Instead of going to [the pharmacy], plants can alter their chemistry and make their own equivalent version of sunscreen compounds. Their chemical structure acts to dissipate the high-energy wavelengths of UV-B light and stops it from getting within the preserved tissues of the pollen grains.”

Related: 3.5 billion-year-old rock structures are one of the oldest signs of life on Earth

In this case, the radiation spike didn’t “kill the plants outright, but rather it slowed them down by lessening their ability to photosynthesize, which caused them to become sterile over time,” Lomax said. “You then wind up with extinction driven by a lack of sexual reproduction rather than the UV-B frying the plants instantly.”

Experts have long theorized that the Permian-Triassic extinction, classified as one of the five major extinction events on Earth, was in response to a “paleoclimate emergency” caused by the Siberian Traps eruption, a large volcanic event in what is now modern-day Siberia. The catastrophic incident forced plumes of carbon buried deep within the Earth’s interior up into the stratosphere, resulting in a global warming event that “led to a collapse in the Earth’s ozone layer,” according to the researchers.

The pollen grain used in the work. It measures about half the width of a human hair (Image credit: Liu Feng/Nanjing Institute of Geology and Paleontology )

“And when you thin out the ozone layer, that’s when you end up with more UV-Bs,” Lomax said.

In their research, the scientists also discovered a link between the burst of UV-B radiation and how it changed the chemistry of plants’ tissues, which led to “a loss of insect diversity,” Lomax said.RELATED STORIES—After the ‘Great Dying,’ life on Earth took millions of years to recover. Now, scientists know why.

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“In this case, plant tissues became less palatable to herbivores and less digestible,” Lomax said.

Because plant leaves had less nitrogen, they were not nutritious enough for the insects that ate them. That may explain why insect populations plummeted during this extinction event.

“Often insects come out unscathed during mass extinction events, but that wasn’t the case here,” Lomax said.

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Putin has agreed Ukraine can have ‘NATO-style’ security guarantee, Trump envoy says

Published

2 hours ago

August 17, 2025

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Putin has agreed Ukraine can have 'NATO-style' security guarantee, Trump envoy says

Vladimir Putin has agreed to allow Ukraine’s allies to offer it a NATO-like security guarantee as part of an eventual deal to end the war, according to US special envoy Steve Witkoff.

Mr Witkoff said the Russian president agreed to the move when he met with Donald Trump in Alaska on Friday.

Speaking to CNN on Sunday, Mr Witkoff, who was by the US president’s side at the summit, said: “We were able to win the following concession: That the United States could offer Article 5-like protection, which is one of the real reasons why Ukraine wants to be in NATO.”

Article 5 is a core principle of the 32-member collective, which states that an armed attack against one or more of its members shall be considered an attack against all. It has only been invoked once, by the US, in the wake of the 9/11 attacks in 2001.

Russia has repeatedly insisted that Ukraine cannot be allowed to join NATO and has dismissed the idea that NATO member forces could be peacekeepers under some sort of ceasefire deal.

Mr Witkoff, who has previously met with Mr Putin to discuss an end to the Ukraine war, said Friday’s summit was the first time he had heard the Russian president agree to the suggestion of NATO-like protection – and called it “game-changing”.

His comments came as Volodymyr Zelenskyy met with European Commission President Ursula von der Leyen in Brussels.

The Ukrainian president said in a post on X: “This is a historic decision that the United States is ready to take part in security guarantees for Ukraine.

“Security guarantees, as a result of our joint work, must really be very practical, delivering protection on land, in the air, and at sea, and must be developed with Europe’s participation.”

Ms von der Leyen, speaking at a news conference with the Ukrainian president, said the European Union “is ready to do its share”.

EU leaders to join Zelenskyy at White House

Sunday afternoon also saw Ms von der Leyen and Mr Zelenskyy dial in to a meeting with the coalition of the willing, a peacekeeping alliance of European leaders – some of whom will accompany Mr Zelenskyy to meet with Mr Trump tomorrow.

Ms von der Leyen will be at the crunch talks in Washington DC, as will Sir Keir Starmer, France’s Emmanuel Macron and Italy’s Giorgia Meloni.

Germany’s Chancellor Friedrich Merz and NATO Secretary General Mark Rutte will also be in attendance, after the US president reportedly extended an invitation to European leaders.

Mr Putin has reportedly made demands to take control of the eastern Donetsk and Luhansk regions of Ukraine during his summit with Mr Trump as a condition for ending the war.

In exchange, Russia would give up other Ukrainian territories held by its troops, according to several news reports citing sources close to the matter.

Russian troops currently occupy large parts of the two regions and, in September 2022, Moscow announced it was officially annexing them, alongside the Kherson and Zaporizhia regions, in a move rejected and condemned as illegal by the West.

Mr Trump is said to be planning to urge Mr Zelenskyy to agree to the conditions as part of a peace deal to end the war.

That’s despite the Ukrainian president previously ruling out formally handing any territory to Moscow, which he says would be impossible under the country’s constitution, and would deprive Ukraine of defensive lines and open the way for Moscow to conduct further offensives.

In coordinated statements following the Alaska summit, European leaders said Mr Zelenskyy must play a greater role in future talks, and that peace cannot be achieved without him.

The US president said the Washington talk with Mr Zelenskyy could potentially pave the way for a three-way meeting with Mr Putin.

On Saturday, Downing Street insisted Sir Keir and other allies stand ready to support the next phase of talks to end the war.

“At the meeting that will take place at the White House tomorrow, the Prime Minister, with other European partners, stands ready to support this next phase of further talks and will reaffirm that his backing for Ukraine will continue as long as it takes,” a statement from No 10 said.

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