Fossil pollen ties plant life’s two biggest turnovers to extreme ancient warmth

Fossil pollen and spore records from southeastern Australia, northeastern Africa and the American tropics, corrected for uneven sampling, place most first and last appearances of land-plant types over the past 120 million years inside two brief hot spells, an association that does not show how heat did it.

Peer reviewed · Meta-analysis of published fossil records · Deep-time association, not a forecast

Most of the big reshuffles in land-plant life over the past 120 million years happened during two short spells of extreme global warmth, according to a study published on 14 October 2026 in Nature Plants. Kale Sniderman of the University of Melbourne, Gregory Jordan of the University of Tasmania and Chris Mays of the Natural History Museum Vienna and University College Cork corrected decades of fossil pollen and spore counts for uneven sampling. Cooler stretches showed little change. The result is a statistical link across a few dozen slices of time, and it does not test today’s extinction risk.

Evidence at a glance

Is this a big deal?

It is a solid step, and a bold one. Most earlier pollen studies with this kind of correction covered no more than about 45 million years, according to the paper’s Supplementary Information, and the authors question the one longer New Zealand analysis. A record running from about 130 million years ago to about 7 million years ago is rare. The title says warmth “triggered” the turnovers. The evidence is timing and model fit, so read that verb as the authors’ interpretation.

What scientists found

Fossil pollen and spores are tough, tiny and made in huge numbers, so they survive in rock where leaves and flowers do not. Palaeontologists track the first and last appearance of each pollen or spore type through the layers. A burst of both is called turnover: old types vanish while new ones arrive.

The abstract reports that turnover in every land-plant group was concentrated within brief mid-Cretaceous and early Cenozoic episodes of extreme global warmth, synchronized across high and low latitudes. In the authors’ response to reviewers, those episodes are the late Cenomanian to Turonian (roughly 96 to 90 million years ago) and the late Paleocene to early or middle Eocene. “In contrast, cooler climates were marked by little change,” Jordan said in the University of Melbourne release.

Each hot spell lasted a few million years, according to Jordan. Squeeze the last 120 million years into a 24-hour day, and a 2-to-5-million-year burst lasts about 24 to 60 minutes (SciQuest calculation: one hour equals 5 million years).

How they found it

The project grew out of a collaboration Sniderman and Jordan began in 2008, according to the paper’s author contributions. Southeastern Australia was the anchor: 112 sites, many of them drill cores, spread across 18 pollen zones from 132.6 million to 7.3 million years ago. The team dropped the youngest 7 million years because recent pollen is named in a different, modern-plant style that would distort the counts. Fourteen sites in northeastern Africa, including Egypt and the Muglad rift basin, covered 123 to 66 million years ago in seven bins, and a published Neotropical record covered the Cenozoic.

The University of Melbourne release puts the total at more than 60,000 fossil occurrences. The paper’s free sections do not give a total, and one reviewer described an earlier version’s database as “~140K records,” so the number depends on what is counted.

Raw counts mislead because some periods have far more rock and far more study. “Simple counts of fossilised species can give a misleading sense of diversity over evolutionary time,” Sniderman said in the release. Think of two birdwatchers, one out for an hour and one for a day; the second lists more species without the forest being richer. The team’s fix, shareholder quorum subsampling, compares every time slice at the same level of completeness rather than the same effort, repeated 1,000 times. The analogy has a limit: unlike a birdwatcher, the method cannot see plants that left no pollen in the rocks at all.

They then fitted statistical models with three kinds of predictor: ocean temperatures reconstructed from fossil plankton shells, the diversity of the other plant groups, and geography (distance to the nearest landmass and palaeolatitude). For southeastern Australia, allowing climate predictors improved the fit in 16 of 18 comparisons. Plant-group diversity did so in 8 and geography in 6 (Supplementary Table 2). In the Neotropics, a pollen origination index tracked global mean surface temperature with a correlation of 0.647 across 20 bins of 3 million years (P = 0.044 after adjusting for autocorrelation).

Why it matters to you

This won’t change anything you do this year. It speaks to the “wonder” question of how today’s plant life came to be. Sniderman said flowering plants number about 400,000 species and dominate most ecosystems on land, so most of the crops, gardens and forests around you belong to the group whose rise this study links to those hot spells.

It also touches climate, but carefully. The study is about change over millions of years, and none of its tests concern today’s warming. Mays drew the modern contrast himself in the release, saying human-driven warming is much faster and likely to cause plant extinctions faster than the ancient events: “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.” That is his interpretation, not a result of the paper.

What the evidence does not show

It does not show how heat produced turnover. The authors replaced many references to warm temperatures with “greenhouse climates” to include a faster water cycle and other changes that come with very warm periods, according to their response to reviewers.

It does not count species. The Supplementary Information says pollen types seen under a light microscope usually match plant genera or families, so true species turnover was probably larger than the counts show.

It is mostly one region. Seven African time bins were too few for full model comparison, the authors note, and the African and Neotropical records meet at the 66-million-year boundary with a break rather than overlapping.

It does not measure dominance. Diversity counts which types exist, not how much of the forest they make up.

How this fits what we already knew

The abstract notes that flowering plants’ rise to ecological dominance was delayed until the early Cenozoic, tens of millions of years after their major groups emerged. Some scientists had proposed that early Cenozoic heat was the trigger; others pointed to steps in flowering-plant evolution that happened in cool times.

The new record also bears on the dinosaur-ending impact. In their response to reviewers, the authors write that their results give no support to the idea that losses at the K–Pg boundary let flowering plants finish their rise. In southeastern Australia, angiosperm pollen diversity grew about four-fold from roughly 4 fossil species between 86 and 81 million years ago, then about doubled again in the early Cenozoic hot spell, when it reached its high plateau.

Outside view: what the peer reviewers said

SciQuest has not interviewed an independent scientist for this same-day story. The best outside view comes from the published Peer Review File. Carlos Jaramillo, one of two reviewers and the only one who signed, called it “an excellent study”. He also warned that sea-level changes in the Turonian could alter which pollen reaches a site, a possible artefact the authors answered with more detail on rock types. He added that “Diversity and biomass dominance are not correlated”, and the authors toned down their dominance claims. After revision he wrote: “I also was able to find the raw data, run the code and replicate the results.” Jaramillo is also thanked in the paper for sharing or discussing pollen data, so he is not fully independent.

The second, anonymous reviewer saw no reason to reject the conclusions. That reviewer pointed out that a joined African and Colombian record could instead show a big turnover at the K–Pg boundary and none in the Paleocene–Eocene. The reviewer also asked for a New Zealand comparison; the authors argued that record has data-quality problems.

How other headlines framed it

• The University of Melbourne release called climate change “the important driver” of plant diversity and said the two hot spells were the warmest of the past 140 million years.
• Phys.org, reposting the release, used a softer headline: ancient climate shifts “may explain” flowering plants’ diversity.
• Mirage News, an aggregator, went further with a headline saying climate change drives plant diversity.

The release mixes 140 and 130 million years. The paper’s title says 120; the Australian data begin about 130 million years ago, and none of the paper’s free material gives 140.

What happens next

The data and R code are public on Figshare, so other groups can rerun the analysis or add regions. A New Zealand record and a continuous South American record through the K–Pg boundary, both raised by the reviewers, are the obvious tests. For another deep-time puzzle written in rock layers, see how a vanished cliff may explain the Grand Canyon’s missing billion years.

In one sentence

Corrected fossil pollen records suggest plant life reshuffled mainly during two short, extremely hot spells, but that is a link in timing, not proof of how heat did it or what today’s faster warming will do.

Read next

• What was the asteroid that killed the dinosaurs?, the K–Pg event this record finds less important for plants
• Jurassic swimming mammal relative hints suckling anatomy evolved early, another fossil story from the age of dinosaurs
• Nature-based solutions to climate change, on what plants can and cannot do for today’s climate

Sources and disclosure

1. Sniderman JMK, Jordan GJ, Mays C. “Extreme greenhouse warmth triggered the two major floristic turnover events of the past 120 million years.” Nature Plants, published online 14 October 2026. doi:10.1038/s41477-026-02429-y. Abstract and figure captions read; main text paywalled.
2. Supplementary Information (methods, Supplementary Tables 1–5) and Peer Review File (CC BY 4.0), Nature Plants, 2026.
3. Sniderman JMK. Data and R code repository. Figshare, 2026. doi:10.6084/m9.figshare.29614958
4. University of Melbourne. “Why are there so many plants? Climate change is the important driver”, EurekAlert!, 14 October 2026.
5. International Commission on Stratigraphy. International Chronostratigraphic Chart (stage ages used for the graphic’s band edges).

Disclosure: This article was drafted with AI assistance and checked against the sources above. The graphic is a SciQuest original built from the paper’s supplementary tables; the 24-hour comparison is a SciQuest calculation. Peer-review quotes come from Nature Plants’ published Peer Review File; author quotes come from the University of Melbourne release, not SciQuest interviews. SciQuest has no conflicts of interest. Spotted an error? See our corrections policy.