Warming climates force plants to compete with each other

Climate change is reshaping ecosystems at an alarming rate. While much attention goes to the loss of animal species, plants are also vanishing. Since 1750, around 600 plant species have gone extinct, a number twice as high as animal extinctions.

Yet, little is known about which plants are most at risk and how biodiversity shifts affect ecosystems.

Scientists from the Alfred Wegener Institute have taken a deep look into the past to answer these questions. Using ancient DNA preserved in lake sediments, they reconstructed how plant life changed between 15,000 and 11,000 years ago, a period of significant global warming.

This research, recently published in the journal Nature Communications, sheds light on how past extinctions could predict future biodiversity loss. The study provides a clearer picture of how plant communities shift under warming conditions and what this could mean for ecosystems today.

The forgotten side of plant extinction

The loss of plants rarely makes headlines, even though they form the foundation of life. Many people recognize the extinction of large mammals like the woolly mammoth, but few think about the plants that vanished alongside them.

This oversight is partly due to the difficulty of studying plant extinctions. Traditional methods rely on fossilized pollen, which cannot always identify individual species.

“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,” said Professor Ulrike Herzschuh from the Alfred Wegener Institute. “Until recently, we lacked suitable methods for investigating the extinction of plant species in detail.”

To overcome this challenge, the researchers used advanced techniques to extract and analyze ancient DNA from lake sediments. These sediments contain genetic material from plants that lived up to 30,000 years ago.

By enriching and sequencing these DNA fragments, scientists could compare them with modern databases and reconstruct past plant communities.

Climate change alters plant interactions

Shifts in climate do not just affect which plants survive but also how they interact with one another. The research revealed that plant communities undergo drastic transformations as temperatures change.

“We’ve now been able to determine in detail when and where species appeared and disappeared in Alaska and Siberia,” noted 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.”

One of the most striking findings was the shift in how plants interact. During cold periods, plants often support each other, creating environments where multiple species can thrive and reduce the risk of extinction.

However, in warm periods, competition becomes dominant. This pattern is still visible today in tundra regions where cushion plants provide shelter for other species.

“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,” said Herzschuh. This sheltering effect was essential for biodiversity in colder climates.

Self-destructive cycle for Arctic plants

Today, cushion plants continue to play a vital role in Arctic ecosystems. However, their ability to help other plants survive could ultimately lead to their own decline.

As Arctic temperatures rise, trees and shrubs are expanding into tundra regions where cushion plants once dominated. These larger plants benefit from the shelter cushion plants provide, allowing them to spread more quickly.

“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,” noted the study authors.

This unintended consequence of plant interactions highlights the delicate balance of Arctic ecosystems. While cushion plants once promoted diversity, they may now accelerate their own disappearance by aiding the spread of larger, more competitive species.

The plants most at risk of extinction

The study also sought to determine which plant species are most vulnerable to extinction. At the end of the last ice age, some plant communities vanished entirely. One of the most notable losses was the mammoth steppe, a vast ecosystem that once stretched across the Northern Hemisphere.

Identifying extinct plants proved difficult because genetic databases focus on modern species. “To identify the species that no longer existed, we had to use a trick,” said Herzschuh.

The researchers examined all DNA fragments from sediment samples, then used statistical models to isolate DNA that did not match any known modern species.

Through this method, they found that grasses and shrubs face the highest risk of extinction in a warming world. Unlike woody plants, which can spread into new areas as temperatures rise, these smaller species often struggle to compete.

Additionally, plants in regions with high biodiversity are more vulnerable than those in less diverse environments.

One surprising discovery was that plant extinction rates peaked at the beginning of the current warm phase. Often, species disappeared thousands of years after the initial environmental changes.

“That means the full impacts of today’s human activities might not become apparent until the distant future,” said the researchers.

What this means for today’s Arctic

The findings provide essential insights into how climate change affects biodiversity.

For the first time, scientists have been able to measure plant extinction rates, offering valuable reference data for predicting future changes. The results indicate that Arctic ecosystems are particularly at risk as temperatures continue to rise.

“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,” said Herzschuh.

By studying ancient DNA, researchers can uncover the long-term effects of climate change on plant communities. This knowledge is crucial for conservation efforts and for understanding how ecosystems will respond to further warming.

The lessons from the past suggest that the most significant impacts of climate change on plant biodiversity are yet to come.

The study is published in the journal Nature Communications.

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