Arctic Boreal Zone Becomes a Carbon Source

January 22, 2025

Recent research has revealed shift in the Arctic Boreal Zone, revealing that nearly 40% of this region has transitioned from a carbon sink to a carbon source. This transformation is primarily driven by climate change, resulting in longer growing seasons, increased microbial activity, and a rise in wildfires. The findings suggest that these changes could have dire implications for global climate regulation.

Carbon Sink vs. Carbon Source

A carbon sink absorbs more carbon dioxide than it releases.
Conversely, a carbon source emits more than it absorbs.
The Arctic, once carbon sink, is now increasingly releasing carbon, contributing to global warming.

Research Findings

A study published in *Nature Climate Change* analysed data from 200 monitoring sites between 1990 and 2020. It found that over 30% of the Arctic Boreal Zone is now a net carbon source, with fire emissions increasing this figure to 40%.

Geographical Distribution

Carbon source areas are primarily located in Alaska (44%), northern Europe (25%), Canada (19%), and Siberia (13%). The emissions are particularly notable during the non-summer months, outweighing carbon absorption in summer.

Impact of Warming Temperatures

Warming temperatures are causing permafrost to thaw, releasing vast amounts of stored carbon. This process exacerbates climate change, as the Arctic tundra transitions to a net carbon source.

Changes in Vegetation

The Arctic Boreal Zone has experienced “greening,” with 49% showing longer growing seasons. However, only 12% acts as a net carbon sink annually, limiting carbon absorption capabilities.

Boreal Forest Vulnerability

Boreal forests, spanning Canada, Alaska, and Siberia, are warming four times faster than the global average. This rapid change makes them increasingly vulnerable to wildfires and alters their role as carbon sinks.

Tree Cover Dynamics

A study from Wageningen University analysed tree cover data from 2000 to 2020. It identified two modes of tree cover – low-density (5-15%) and high-density (over 60%). Warmer regions are seeing declines in dense cover, while colder areas are experiencing increases.

Future Projections

By 2100, boreal forests are expected to stabilise at intermediate tree cover levels, ranging from 30-50% in warmer areas to 25-30% in colder regions. The shift towards open forests could enhance carbon uptake, but also increase fire risks.

Fire Risks and Ecosystem Changes

Open forests are more susceptible to wildfires due to increased flammability. The transition to this state could complicate predictions of fire behaviour and ecosystem dynamics, reducing the boreal biome’s ability to regulate climate.

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