Northern Eurasia holds roughly a fifth of the planet’s forests, and those forests are doing serious work pulling carbon dioxide out of the air.
You’d think the places warming fastest would be soaking up the most extra carbon as a result.
New research shows that’s not actually what’s happening, and the real explanation comes down to something surprisingly down-to-earth: how healthy the forest itself is.
The study was led by Irina Melnikova from the University of Tsukuba and colleagues.
These forests help quite a lot when it comes to slowing climate change, but figuring out exactly how their carbon absorption behaves has been genuinely tricky.
This difficulty stems from how much things such as rapid warming, wildfires, and changing land use are entangled.
________________________________________________________________________
Pulling together the available evidence
To get past that mess, the researchers combined evidence from a whole stack of independent sources at once.
They analyzed satellite data, atmospheric inversion models, dynamic vegetation models, and full Earth System models.
These approaches don’t always agree with each other, since each one carries its own assumptions and blind spots.
Yet this time, despite real differences, they landed on roughly the same answer.
Northern Eurasian ecosystems absorb about 0.47 billion tons of carbon a year, give or take 0.20 billion tons, based on data from 2001 through 2015.
That’s close to a third of the entire planet’s terrestrial carbon sink, coming from just one region, a genuinely striking share for one part of the world to carry.
Warming forests and carbon storage
There’s a pretty intuitive assumption in climate science: warm up a cold place, and its plants should get busier, pulling in more carbon as growing seasons stretch out and photosynthesis ramps up.
This study pokes a real hole in that logic. The strongest carbon sinks actually sit in the western and southern parts of Northern Eurasia.
Carbon uptake gets weaker and weaker as you head toward the colder northeastern regions, exactly the places warming fastest on the entire planet.
Every single modeling approach the team used showed the same shape: carbon uptake climbs, peaks, then drops off as you move along both temperature and latitude gradients.
The sweet spot landed in areas with average temperatures above freezing and warming levels between 1.2 and 1.5 degrees Celsius.
Past that point, more warming didn’t buy you a stronger carbon sink at all, and in the coldest zones it barely moved the needle.
Fastest-warming forests are underperforming
So why do these rapidly heating northeastern regions are so inefficient in carbon uptake?
Their forests tend to be less productive to begin with and get hit harder by disturbances like wildfire, which regularly wipes out years of accumulated carbon storage in a single season.
There’s also a timing issue: a lot of the warming happening up there is concentrated in winter, when the ground is still frozen solid and plants simply can’t take advantage of it no matter how much the air temperature climbs.
Whatever extra growth does come from warming and rising CO2 gets largely canceled out by increased respiration from soil microbes and carbon escaping as permafrost thaws.
And even though the eastern half of Northern Eurasia actually has more total forest area than the west, those eastern forests carry less timber volume, skew older, burn more often, and just aren’t as productive overall.
The importance of forest quality
The researchers point to differences in forest productivity as the real explanation here, something foresters in Russia and Northern Europe have a word for: bonitet.
It’s basically a grading system for how good a patch of land is at growing trees, factoring in tree height, timber volume, biomass, and sometimes the soil and habitat conditions underneath it all.
Forests with a high bonitet rating, already carrying substantial carbon stocks, end up doing most of the heavy lifting for the region’s overall carbon sink.
Lower-quality forests barely respond to warming at all, even in the places heating up the fastest.
In other words, cranking up the temperature doesn’t magically turn a weak, unproductive forest into a strong one, no matter how many degrees get added to the average.
What this means going forward
The takeaway here is fairly significant. Forest productivity, not the speed of warming itself, looks like the real deciding factor in how Northern Eurasia’s carbon sink will hold up as the climate keeps shifting.
This flips a common assumption on its head. The regions warming the most aren’t necessarily the ones stepping up to absorb more carbon.
Instead, what happens next may hinge less on the thermometer and more on the actual condition of the forests themselves.
The study is published in the journal Global Biochemical Cycles.
NOTE – This article was originally published in Earth and can be viewed here
