Northern Eurasia holds roughly 20 percent of the world's forests. Those forests absorb a significant share of the planet's excess carbon dioxide. But a new study shows that the warmest and fastest-changing parts of that region are not necessarily the ones doing the most work.
According to research published in the journal Global Biogeochemical Cycles, Northern Eurasian ecosystems absorb approximately 0.47 plus or minus 0.20 billion tonnes of carbon each year. That figure represents nearly one-third of the global terrestrial carbon sink, making the region one of the most important on Earth for climate regulation.
The study, conducted with support from the University of Tsukuba and reported by Phys.org, pulled together evidence from multiple independent sources. Researchers used satellite observations, data-driven products, atmospheric inversion models, dynamic global vegetation models, and Earth system models. Despite substantial differences among those data sources, broad agreement emerged on the overall absorption figure and on which parts of the region are doing the most absorbing.
The results challenge a widely held assumption. Many scientists have expected that faster warming in cold regions would strengthen carbon sinks there, because warmer temperatures should extend the growing season and boost plant activity. The study found the opposite pattern. The strongest carbon sinks occur in the western and southern parts of Northern Eurasia. Moving toward the colder northeastern regions, the carbon sinks progressively weaken.
Several factors help explain that finding. Forests in the cold northeastern regions are generally less productive and more vulnerable to disturbance. Wildfires are one major factor. When a fire burns through a less productive forest, it can release stored carbon quickly and take a long time to recover. More productive forests with larger carbon stocks can absorb more carbon and bounce back from disturbance more effectively.
The timing of warming also matters. Much of the temperature increase in the coldest northeastern zones happens during winter months. In winter, soils remain frozen and biological activity slows dramatically. Carbon uptake during that season is limited regardless of how warm the air gets. Warmer winters do not translate directly into more carbon absorption when the ground itself is locked in permafrost conditions.
The study introduces the concept of forest productivity, sometimes described using the Russian term bonitet or as site quality, as the key factor shaping how much carbon a given area absorbs. High-productivity forests contribute disproportionately to the regional carbon sink. Low-productivity forests show only limited improvement even when temperatures rise rapidly around them.
Researchers found that this productivity gap helps explain why the northeastern regions, despite being among the fastest-warming places on Earth, do not contribute proportionally to strengthening the overall Northern Eurasian carbon sink. The relationship between warming and carbon absorption is not linear. It depends heavily on the underlying capacity of the forest to grow and store carbon in the first place.
The findings carry weight for climate projections. If models assume that warming automatically strengthens carbon sinks in cold regions, they may overestimate how much carbon Northern Eurasia will absorb as temperatures continue to rise. The actual trajectory will depend on where productive forests are, how disturbances like wildfires change over time, and whether site quality in colder regions improves alongside warming or stays constrained by other factors such as soil conditions and permafrost.
The study was led by I. Melnikova and colleagues and published under the full title Land Carbon Sink Distribution in Northern Eurasia Is Driven by Climate Change in Global Biogeochemical Cycles in 2026.
