Arctic and boreal ecosystems are becoming increasingly unstable

Major transformations are occurring within Arctic and boreal ecosystems, which are warming at a faster rate than the rest of the planet.

Recent findings from the University of California, Irvine, detailed in three pivotal studies, underscore the significant environmental shifts prompted by global warming.

The research, led by PhD candidate Jinhyuk Kim and Professor James Randerson, suggests that ecosystems at high latitudes are becoming increasingly unstable.

Wildfires ignite change across ecosystems

The study was focused on the forests of Canada and Alaska. The researchers found that wildfires are intensifying photosynthesis rates. This phenomenon arises as fast-growing deciduous plants like willow and aspen replace the slower-growing black spruce forests destroyed by fire.

“We’re seeing higher levels of photosynthesis that persist for decades after fire,” explained Kim. “Instead of the evergreen conifer forest coming back right away, in some regions, we see a long-term replacement of these forests with faster-growing species.”

Complex consequences of wildfires

While increased photosynthesis might suggest a greater removal of carbon dioxide from the atmosphere, the reality is much more complex.

“But because you’ve combusted the carbon stored in the plants and their organic soils, even the increase in photosynthesis we observe doesn’t necessarily translate into more carbon storage in the long run,” explained Kim.

“The increasing trends in wildfire have significant implications for forest species composition and ecosystem function but likely negatively affect the land carbon sink.”

“This is why it’s important to study how the changing landscape from wildfire and warming influences different aspects of land carbon cycling.”

Tracking changes in Arctic and boreal ecosystems

To track changes in photosynthesis, Kim’s team utilized data from the Orbiting Carbon Observatory 2 satellites. These satellites measure plant fluorescence – a novel method that provides a global view of photosynthesis rates.

“We also have this long land cover time series from Landsat, and we can look at how fires are changing the land plant cover and then tie it to changes in the solar-induced fluorescence signal,” said Kim.

“We find that wildfires are changing the land cover, which, in turn, can enhance the seasonality of carbon fluxes at large spatial scales.”

Shifting shrubbery signals warmer winters

In another study led by Allison Welch, a PhD candidate in the lab of Professor Claudia Czimczik, researchers explored plant expansion across the Arctic ecosystem.

“With increasing temperatures and wildfire activity, we’re seeing increased growth of bigger, deciduous shrubs,” noted Welch.

Her team found that alder shrubs, in particular, are thriving, significantly boosting vegetation productivity at their study sites. Moreover, these changes come with critical implications for permafrost.

“We reported a decrease in the thickness of the organic layer at our tundra sites,” said Welch. “Shallower organic layers mean less insulation for the underlying Arctic permafrost, which carries vast reserves of frozen organic matter that, if thawed, may release planet-warming gases like carbon dioxide into the atmosphere.”

Chemical clues about ecosystem changes

Under the guidance of Professor Alex Guenther, PhD candidate Hui Wang conducted a third study. The research was focused on an unexpected rise in emissions of isoprene – an important molecule that influences local climate through its effects on ozone, aerosols, and methane levels.

“This change will indirectly change the climate,” said Wang. He noted that rising temperatures have prompted plants to release more isoprene.

Rapidly changing Arctic ecosystem

These studies collectively highlight a rapidly changing Arctic ecosystem that is transforming at a faster rate than previously anticipated. Claudia Czimczik, a co-author on Welch’s paper, emphasized the urgent need for attention.

“These three studies are examples of how the Arctic is changing more rapidly than previously expected. Increasing wildfire activity, via its effect on vegetation composition, has the potential to accelerate permafrost thaw beyond the rates we expected from changing climate,” said Czimczik.

Kim concluded with a reflection on the broader implications of the research. “We can see the environment is unstable, and that there are complex interactions from not only the changing plant communities but the responses of those plants to the rapidly changing climate.”

“These have consequences for the environment and the overall Earth system, so it’s something important that we need to understand better.”

The research is published in the journal Global Change Biology.

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