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The phenomenon of global warming is leading to an alarming decline in plant species, with estimates suggesting that around 600 types have become extinct since 1750, a figure that is double that of animal species lost in the same period. This raises questions about which specific plants are most affected and the implications of altered biodiversity on plant interactions. Researchers at the Alfred Wegener Institute have sought to answer these queries through two recent studies, utilizing ancient genetic material found in lake sediments to reveal how plant life transformed approximately 15,000 to 11,000 years ago, coinciding with the warming period following the last ice age, known as a significant mass extinction event. Insights gained from this historical context may provide clues about future scenarios. Their findings were published in the journal Nature Communications.
“While the extinction of iconic species like the woolly mammoth is commonly recognized, the loss of plant species during the last ice age often goes unnoticed,” remarks Prof Ulrike Herzschuh from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI). “Previously, we lacked the precise methods to explore the extinction of plant species in-depth.” Traditional fossil analysis primarily focused on pollen, which doesn’t allow for species-specific identification, thus missing critical insights into which plants became extinct. Through advanced techniques, the researchers analyzed DNA from sediment cores gathered from lakes in Alaska and Siberia, allowing them to reconstruct historical changes in vegetation in these areas.
Temperature can change how plants interact
“Our research has detailed when and where specific plant species appeared and vanished in Alaska and Siberia,” explains Ulrike Herzschuh. “The findings reveal substantial shifts in plant composition at the end of the last ice age, which were linked to significant ecological changes.” Notably, the researchers discovered a relationship between temperature fluctuations and plant interactions; during colder periods, plants tend to support one another, whereas during warmer times, competition becomes the norm. “We identified a presence of cushion plants within the sediment DNA, which likely played a role in facilitating the growth of other species by creating sheltered environments,” adds Herzschuh. This dynamic has significant implications for both biodiversity and species distribution.
In contrast, warmer climates tend to promote the dominance of woody plants. “Currently, we are witnessing a decline in plant diversity as trees and shrubs encroach upon tundra regions, whereas past cold periods exhibited greater plant diversity,” observes Herzschuh. This raises questions about the future of vegetation in high-latitude regions, where cushion plants remain crucial. In the modern Arctic, these plants could unwittingly threaten their own survival as warming conditions allow woody plants to thrive in areas they previously could not. “As Arctic temperatures continue to rise, the expansion of woody species could outpace the cushion plants, putting them at greater risk of extinction,” notes Herzschuh.
Which plant species are particularly at risk?
The transition following the last ice age also resulted in the complete disappearance of certain vegetation types, a finding confirmed by the researchers’ innovative techniques. For instance, the mammoth steppe, which flourished during the last ice age, vanished during the shift to the current era. Identifying extinct plant species posed unique challenges. “To pinpoint species that are no longer present, we had to employ a clever approach,” explains Herzschuh. “Typically, species identification relies on comparing DNA fragments with today’s genetic databases, which do not account for extinct species. Therefore, we meticulously analyzed all DNA fragments from our sediment cores and applied statistical models to isolate those with clear links to contemporary plants.”
This method also yielded insights into which species may face the greatest risk of disappearing in a warming climate. Grasses and shrubs are particularly vulnerable, as they tend to be less capable of dispersing than their woody counterparts, which can thrive and expand their range as temperatures rise. Furthermore, species that inhabit areas of high biodiversity are often at a greater risk than more common ones. Interestingly, the research revealed that extinction rates peaked at the onset of the current warm phase, sometimes lagging several thousand years behind the environmental changes themselves. This suggests that the full repercussions of modern human activity on plant species may not be fully realized until far into the future.
Relevance for today’s Arctic
The outcomes of these studies provide critical insights into how climate-related environmental shifts influence biodiversity and the underlying mechanisms at play. For the first time, researchers have been able to assess extinction rates among plant species, establishing a baseline that will aid in evaluating ongoing changes within Arctic ecosystems. “Our research underscores the necessity of understanding biodiversity and ecological relationships over the long term to better forecast the consequences of climate change,” concludes Ulrike Herzschuh. “The ancient DNA retrieved from sediments offers vital knowledge essential for this understanding.”
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