Throughout the southern reaches of the Arctic, plants are getting taller due to climate change.

Peltigera aphthosa.

The common freckle pelt lichen (Peltigera aphthosa) is often found on mossy ground, rocks, or under trees in Arctic ecosystems.
Image credits James Walton / NPS.

While not graced with the lush vegetation of the Earth’s other areas, the Arctic is far from desolate. Hundreds of species of low-lying shrubs, grasses, and other plants make a home in the frigid expanse, and they play a key role in the carbon cycle. However, anthropic climate change is causing new plants to move into the Arctic’s southern stretches which, according to a new paper, can lead to quite a bit of hassle in the future.

Growing (too) strong

An international team of 130 researchers, led by Dr Isla Myers-Smith of the School of Geosciences at the University of Edinburgh, and Dr Anne Bjorkman from the Senckenberg Biodiversity and Climate Research Centre (BiK-F) in Frankfurt, has been investigating the Arctic flora as part of a Natural Environment Research Council (NERC)-funded project.

The team looked at more than 60,000 data points from hundreds of sites across the Arctic and alpine tundra and report that higher mean temperatures are impacting the delicate balance of these ecosystems. This is the first time that a biome-scale study looking at the role plants play in this rapidly-warming part of the planet has been carried out, says Bjorkman.

“Rapid climate warming in the Arctic and alpine regions is driving changes in the structure and composition of plant communities, with important consequences for how this vast and sensitive ecosystem functions,” Dr Bjorkman adds.

“Arctic regions have long been a focus for climate change research, as the permafrost lying under the northern latitudes contains 30 to 50 percent of the world’s soil carbon”.

Among other things, plants insulate the soil they grow in from incoming sunlight. While this is rather fortunate for us during a hot summer’s day, in the Arctic, it’s a matter of ecosystem stability. Taller plants also help to trap more snow beneath their leaves. This thicker blanket of snow, in turn, further insulates the soil from temperature changes in the atmosphere, preventing it from freezing.

In other words, taller plants in the Arctic keep soil thawed for more days each year, leading to “an increase in the release of greenhouse gases” as biological matter trapped in the soil has a wider window of time annually to decompose.

“If taller plants continue to increase at the current rate, the plant community height could increase by 20 to 60 percent by the end of the century,” Dr Bjorkman explains.

The team gathered their data from sites in Alaska, Canada, Iceland, Scandinavia, and Russia. Alpine sites in the European Alps and Colorado Rockies were also included in the study. For each dataset, the team looked at the relationship between temperature and soil moisture. They also tracked plant height and leaf area, along with specific leaf area, leaf nitrogen content, leaf dry matter content, as well as ‘woodiness and evergreenness’.

Out of all these characteristics, only height increased meaningfully over time. Temperature and moisture levels (which is strongly affected by temperature) had the strongest influence on observed plant characteristics.

“We need to understand more about soil moisture in the Arctic. Precipitation is likely to increase in the region, but that’s just one factor that affects soil moisture levels,” Dr Myers-Smith said. “While most climate change models and research have focused on increasing temperatures, our research has shown that soil moisture can play a much greater role in changing plant traits than we previously thought.”

The results suggest that (through the mechanism explained previously), this increase in overall plant height could have significant implications for both the Arctic and the world at large. At the same time, they should help us better tailor our climate models, to take into account increased greenhouse gas emissions from the area.

The paper “Plant functional trait change across a warming tundra biome” has been published in the journal Nature.

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