Most plant extinctions and new species in the pollen record fall in two extremely warm intervals
Australian and Austrian researchers found plant extinctions and new species clustered in the two warmest intervals of the past 140 million years. They say it could explain flowering-plant dominance, a step the fossil evidence does not yet show.
The Scientist · Science desk
What happened
- The Nature Plants study used fossil pollen and spores and names the mid-Cretaceous and the early Cenozoic as the two intervals of extreme warmth central to plant evolution.
- The team compiled over 60,000 individual fossil occurrences and applied methods that, the researchers say, overcome the major biases in the fossil record.
- Cooler climates showed little change, and competing explanations such as plant-group interactions or geographic isolation fit the diversity trends less well than climate.
- Co-author Chris Mays says current human-driven warming is occurring much faster than during the two past warm intervals.
Why it matters
- contradiction The result is offered as a possible explanation for flowering-plant dominance, yet the same warm-interval turnover appears in the other main land plant groups, so it cannot by itself single out flowering plants.
- constraint The record resolves intervals of a few million years, so how fast modern warming would remove species is inferred from the warming rate and cannot be read off this record.
- decision Anyone weighing a fossil-based claim that climate drove diversity has to ask how sampling was corrected, since simple species counts can mislead.
Raw fossil counts are the obstacle the authors had to get around. Sniderman, the lead author, said: "The number of available fossils varies over geological time and between regions. Because of this, simple counts of fossilized species can give a misleading sense of diversity over evolutionary time." [5] According to the researchers, that bias is why a clear link between climate and plant diversity had stayed elusive until now [4]. A thinly sampled warm interval would look poor in species whatever the plants were doing.
Jordan, a professor of botany at the University of Tasmania and a co-author, described the timing this way: "Thus, the warmest greenhouse climates simultaneously destroyed and promoted plant diversity, but only when considered over million-year timescales." [7][13] Each of the two turnover intervals lasted a few million years, he said [8].
Flowering plants now number approximately 400,000 species, according to Sniderman [15]. What ties climate to their rise is a timing match: the displacement of older groups began about 100 million years ago, in the mid-Cretaceous, the first of the two warm intervals [16][2]. The thing this doesn't tell you is whether flowering plants took a larger share of the new species in those windows than the older groups did. The summary does not describe that comparison. We think the data make a climate role plausible and leave the cause of dominance open. With two warm intervals there are only two events to set against the cooler stretches [1].
The summary also frames the result over 140 million years, while the revised diversity estimates cover the past 130 [1][12], a difference of 10 million years [14]. Both named warm intervals sit inside the shorter window, since the mid-Cretaceous is about 100 million years back and the early Cenozoic is more recent [2][16].
Mays, curator of paleontology at the Natural History Museum of Vienna, put the modern comparison as a waiting time. He said: "While extinct species will eventually be replaced by new species, not many of us will be satisfied having to wait the few million years for them to evolve, especially since we have the power to prevent the loss of species today" [11][13]. He added that the loss is preventable if emissions from burning fossil fuels stop [11]. The few million years he cites matches the length of each past turnover interval [8].
What to watch
- Whether the authors or others report what share of the new species in each warm interval were flowering plants, compared with the older groups.
- Whether independent re-analyses with different sampling corrections reproduce the two turnover intervals.
- Whether any fossil dataset can time extinctions at a resolution finer than a few million years, which would test the speed question directly.
Clarity's read
What the record supports and how the coverage leans. The claims behind it follow.
Reality
- Evidence58
- Adoption
- Insufficient
- Hype gap+22
- Incentives
- Insufficient
- Confidence50
Claim ledger
Ranked by verification strength, evidence, and original report placement.
- [1]
Researchers in Australia and Austria say the two warmest time periods on Earth in the past 140 million years drove both mass extinctions and explosions in plant diversity, and that this could explain how flowering plants became dominant among land plants.
- [2]
The study, published in Nature Plants, examined fossilized pollen and spores and found that the mid-Cretaceous and early Cenozoic periods of extreme global warmth were central to plant evolution.
- [3]
The turnover pattern applies not only to flowering plants but also to the other main land plant groups.
- [4]
Until now, a clear link between climate and plant diversity had been elusive because of bias in fossil records.
- [5]
"The number of available fossils varies over geological time and between regions. Because of this, simple counts of fossilized species can give a misleading sense of diversity over evolutionary time," Sniderman said.
- [6]
The researchers compiled data on over 60,000 individual fossil occurrences and applied methods that overcome the major biases in the fossil record.
- [7]
"Thus, the warmest greenhouse climates simultaneously destroyed and promoted plant diversity, but only when considered over million-year timescales," said Greg Jordan.
- [8]
Each of the extremely warm turnover intervals lasted a few million years.
- [9]
Cooler climates were marked by little change, and other potential causes of plant diversity trends, such as interactions between plant groups or geographic isolation, did not explain the trends as much as climate did.
- [10]
Chris Mays, curator of paleontology at the Natural History Museum of Vienna and a co-author, says current human-driven warming is occurring much faster than during the mid-Cretaceous and early Cenozoic intervals.
- [11]
Mays said: "While extinct species will eventually be replaced by new species, not many of us will be satisfied having to wait the few million years for them to evolve, especially since we have the power to prevent the loss of species today", and tied that to stopping emissions from burning fossil fuels.
- [12]
The researchers generated revised estimates of fossil pollen and spore diversity for successive time periods throughout the past 130 million years.
- [13]
Greg Jordan is professor of botany at the University of Tasmania and a co-author; Chris Mays is curator of paleontology at the Natural History Museum of Vienna and a co-author.
- [14]
The headline claim covers 140 million years but the revised diversity estimates cover 130 million years, a difference of 10 million years.
- [15]
Lead author Kale Sniderman, honorary research fellow at the University of Melbourne, said flowering plants are the most productive and diverse group of land plants, with approximately 400,000 species globally.
- [16]
In the middle of the Cretaceous Period, around 100 million years ago, flowering plants began to displace older plant groups that had dominated the land for 200 million years before.
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Sources
1 independent publisher whose own reporting we read for this story.
- phys.orgAncient climate shifts may explain why today's flowering plants are so diverse
1 article · October 14, 2026
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