Extreme weather is turning the Arctic brown and could impact on climate change

Plants killed by an extreme event which affected heathland vegetation across northern Norway

In recent years evidence has emerged that increasing numbers of extreme events are causing dieback of Arctic plants – or ‘browning’ – across Arctic regions.

Scientists from the University of Sheffield studying the Arctic – which is warming twice as fast as the global average – have now found that plant dieback following these events could significantly reduce the ability of Arctic ecosystems to help combat climate change.

Scientists have called the damage to Arctic plants following extreme events, such as sudden periods of extreme warmth during winter ‘Arctic browning’.

Previously scientists had accepted increasing summer warmth in the Arctic was encouraging vegetation to grow, turning areas green.

Rachael Treharne, a PhD student in Animal and Plant Sciences at the University of Sheffield, said Arctic browning could influence whether climate change will slow down or accelerate in the future.

“Despite the scale of Arctic browning, until now we knew very little about its impacts on ecosystem carbon balance; the balance between carbon uptake by vegetation and its release from vegetation and soils,” she said.

“This information is critical to understanding the role of Arctic ecosystems in regulating global climate, both now and in the future.”

The study, published in Global Change Biology, assessed the impacts of Arctic browning driven by extreme climatic events.

Researchers looking at heathland in the Lofoten archipelago of Arctic Norway found the area had been affected by two extreme climatic events, one of which caused death of the dominant evergreen vegetation, and the second of which caused an extensive ‘stress response’, visible as high levels of protective anthocyanin (red) pigments in shoots and leaves.

Researchers found Arctic browning driven by extreme climatic events approximately halves the ability of widespread Arctic heathlands to take up carbon dioxide.

Dr Treharne added:

“Many climate models assume an arbitrary level of greening (and therefore increasing CO2 uptake) across the Arctic. The scale of the browning we’ve seen in recent years suggests the reality may be more complex – calling into question our understanding of the role the Arctic plays in global climate, and whether we should expect Arctic ecosystems to slow or accelerate future climate change.”

Scientists now want to carry out further research and upscale the results across the Arctic, to understand and quantify the role that extreme events are playing in overall Arctic browning trends, and therefore predict how changes in their frequency and severity may influence carbon balance in these ecosystems.

To access the full paper, visit: https://bit.ly/2DL9Wc5

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