New analysis methods, applied to ancient plant DNA, reveal how hard-hit plants were and are by global warming

Global warming is producing a rapid loss of plant species – according to estimates, roughly 600 plant species have died out since 1750 – twice the number of animal species lost. But which species are hit hardest? And how does altered biodiversity actually affect interactions between plants? Experts from the Alfred Wegener Institute have tackled these questions and, in two recent studies, presented the answers they found buried in the past: using fragments of plant genetic material (DNA) deposited in lake sediments, they were able to gain new insights into how the composition of flora changed 15,000 to 11,000 years ago during the warming at the end of the last ice age, which is considered to be the last major mass extinction event before today. This comparison can offer an inkling of what might await us in the future. The researchers have just published their findings in the journal Nature Communications. 

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“Everyone knows that the woolly mammoth went extinct, but virtually no-one mentions the plants that were lost at the end of the last ice age,” says Prof Ulrike Herzschuh from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). “Until recently, we lacked suitable methods for investigating the extinction of plant species in detail.” In terms of fossil plant remains, mainly pollen was used, which doesn’t allow individual species to be identified and therefore offers no evidence of which species have died out. “Using cutting-edge methods, we analysed old DNA from sediment cores taken from lakes in Alaska and Siberia, which allowed us to reconstruct the changes in vegetation in these regions.” The cores contain fragmented DNA from deposited plant biomass from the past 30,000 years, which the experts enriched, sequenced, and compared with databases for identification purposes at special-purpose labs for old DNA. 
Temperature can change how plants interact

“We’ve now been able to determine in detail when and where species appeared and disappeared in Alaska and Siberia,” says Ulrike Herzschuh. “Our research shows that the composition of plant species changed substantially at the end of the last ice age, and that this was accompanied by fundamental changes in the ecological conditions.” The researchers identified a connection between temperature and plant-to-plant interactions: in cold climate periods, plant species support one another, while they mainly compete during warm periods. “In the DNA from the lake sediments, we found e.g. many cushion plants, which most likely supported the expansion of other species by forming sheltered habitats,” says Ulrike Herzschuh. This has effects on both biodiversity and richness range size. In a warmer climate, woody plant species dominate: 'Today, we see that plant diversity declines due to the migration of trees and shrubs into tundra regions, whereas during cold periods, higher plant diversity prevailed.
What does that tell us about vegetation changes in the high latitudes, where cushion plants still play a pivotal role today? In today’s Arctic, this supportive quality could actually threaten their own survival. “Since the warming of the Arctic has already progressed quite far, woody plants can survive even in the high latitudes. The cushion plants could facilitate their spreading, hastening their own extinction in the process.”
Which plant species are particularly at risk?

The end of the last ice age also caused some types of vegetation to disappear entirely – as the experts were able to confirm using their new methods. Take the mammoth steppe, for example: during the last ice age, this type of vegetation spread across the Northern Hemisphere, only to die out during the transition to the current age. In this regard, identifying the extinct plant species was especially challenging. “To identify the species that no longer existed, we had to use a trick,” Ulrike Herzschuh explains. Normally, species are identified on the basis of DNA fragments, which are compared with the entries in genetic databases. But these databases include information on today’s plants, not on extinct species. “We examined all the DNA fragments from our cores and then used statistical models to filter out those with unmistakeable similarities to modern plants, step by step.”
This also allowed the experts to determine which species could be at the greatest risk of extinction in a warming world: grasses and shrubs are at a higher risk of disappearing than woody plant species, which can spread further when temperatures rise. In addition, species in regions with high biodiversity are more often at risk than are less “special” species. One surprising finding: the extinction rate was at its highest at the beginning of the current warm phase – often with a delay of several thousand years after the actual environmental changes. “That means the full impacts of today’s human activities might not become apparent until the distant future.”
Relevance for today’s Arctic
The results of the two studies offer fundamental insights into how environmental changes in connection with warming affect biodiversity, and which mechanisms are central in this regard. As such, for the first time the experts were able to determine extinction rates for plants, which can now be used as reference data to better assess the ongoing changes in Arctic ecosystems. “Our studies show how important it is to understand biodiversity and ecological interactions, also in the long term, in order to better predict the impacts of climate change,” Ulrike Herzschuh summarises. “Using the information locked in old DNA from sediments, we can gain the fundamental knowledge needed to do so.” 
Further information:
Courtin, J., Stoof-Leichsenring, K. R., Lisovski, S., Liu, Y., Alsos, I. G., Biskaborn, B., K., Diekmann, B., Melles, M., Wagner B., Pestryakova, L., Russel, J., Huang, Y., Herzschuh, U. (2025). Potential plant extinctions with the loss of the Pleistocene mammoth steppe. Nature Communications (doi:10.1038/s41467-024-55542-x)
This content is taken from Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research

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"Global warming and mass extinctions: What we can learn from plants from the last ice age", MachPrinciple, August 02, 2025, https://machprinciple.com/post/Global-warming-and-mass-extinctions-What-we-can-learn-from-plants-from-the-last-ice-age