Peatlands cover only a few percent of the global land area, but they conserve almost a quarter of all soil carbon and thus play a crucial role in regulating the climate. My colleagues and I have just made the most accurate map yet of the swamp area of the world – its depth, and how much greenhouse gas they have stored. We found that global warming would soon mean that these peatlands would start sending more carbon than they store.
Peatlands form in areas where water-resistant conditions slow down the decomposition of plant material and accumulate peat. This accumulation of carbonaceous plant debris has been particularly strong in northern tundra and taiga areas, where they have helped cool the world climate for more than 10,000 years. Large areas of the majority of frozen (permafrost) peatlands now emerge, allowing the cold-protected carbon to rapidly return to the atmosphere as carbon dioxide and methane.
Geoscientists have long studied peatlands. They have looked at why some areas have peat but others do not, and they have seen how peatlands act as natural archives, allowing us to reconstruct what the climate and vegetation were like in the past (or even what human life was like: a many well-preserved ancient people have been found in peat soils).
[Read: Scientists are homing in on understanding just how sensitive our climate is to CO2]
Scientists have also long recognized that peatlands are important parts of the global carbon cycle and climate. As plants grow, they absorb CO₂ from the atmosphere and because this material accumulates in the peat, there is less carbon in the atmosphere and will cool the climate in the long run.
With all this knowledge about how important northern peatlands are, it is perhaps surprising to learn that, until recently, there was no extensive map of their depth and how much carbon they store. That is why I lead an international group of researchers who have compiled such a map, which we can use to estimate how the peatlands will respond to global warming. Our work is now published in the journal PNAS.
Peatlands are surprisingly difficult to map because their growth is linked to many different local factors, such as how water flows in the landscape. This meant we had to collect more than 7,000 field observations and use new statistical models based on machine learning to make the maps.
We found that peatlands cover about 3.7 million square kilometers. If it were a country, “Peatland” would be slightly larger than India. These peatlands also store about 415 gigatons (billion tons) of carbon – as much as is stored in all the forests and trees of the world combined.
Almost half of this northern peat carbon is currently in permafrost, soil that is frozen all year round. But, as the world warms and permafrost emerges, it causes peatlands to collapse and completely changes how they relate to greenhouse gases. Areas that once cooled the atmosphere by conserving carbon would instead release more of both CO₂ and methane than they stored. We found that the dew projected from future global warming greenhouse gas emissions would cause the carbon dioxide sink of all northern peatlands to oversee and reverse for hundreds of years. The exact timing of this switch is still very uncertain, but it will probably happen in the later half of this century.
There are regions of very extensive permafrost peatlands in Western Siberia and around Hudson Bay in Canada. These unique environments and ecosystems will be fundamentally altered as the permafrost emerges, and their characteristic mix of frozen peatlands and small lakes will be replaced by extensive areas of wet fen.
These changes will cause more CO₂ and methane to be released into the atmosphere, as the previously frozen peat will be available for microbes that degrade it. The thaw will also lead to large losses of peat in rivers and streams, which will affect both the food chains and the biochemistry of inland waters and the Arctic Ocean.
These new findings further reinforce how urgent it is to reduce our emissions rapidly, as the only way to stop permafrost depletion is to curb global warming. There are no geoengineering solutions that can be deployed in these large and remote areas. Our results clearly show that more limited global warming of 1.5 ℃ -2 ℃ would be much less harmful than our current ranges of 3 ℃ -4 ℃ degrees or higher.
This article was republished from The Conversation by Gustaf Hugelius, Senior Lecturer, Physical Geography, University of Stockholm under a Creative Commons license. Read the original article.
Next read:
Problems sleeping? The Netflix for sleep may be your answer to a better night’s rest
Pssst, hey you!
Do you want to receive the sassiest daily tech newsletter every day, in your inbox, for free? Of course you do: sign up for Big Spam here.
