Finnish forests: from CO₂ sink to CO₂ source

A carbon sink is anything that absorbs more carbon from the atmosphere than it releases. Forests are one of the main systems on planet Earth that absorb carbon and release oxygen. However, researchers in Finland are worried as local forests are not a carbon sink anymore.  

According to the report by the Natural Resources Institute of Finland (LUKE), although forest growth continued to exceed felling and natural loss, since 2021 it is no longer enough to counter the increased carbon emissions from forest soil. 

The decline in the carbon sink in Finland began gradually around 2010 and accelerated rapidly from 2018 onwards. Since then, Finland's land use sector has been a source of emissions, the Integrated Carbon Observation System (ICOS) highlights on its website. 

“This is of course worrying news. Finland has based its climate policy partly on the forest sinks and now it seems this sink has disappeared”, Prof. Annalea Lohila, Focal Point of ICOS Finland is quoted as saying. “The annual growth of trees, which used to increase since 1970’s until about 2010, is not increasing anymore… It can be explained at least partly by the age structure of forests. In addition, harvest levels have stayed high.” 

Climate change 

According to the LUKE researchers, global warming is one of the main reasons for the worrying trend, as rising temperatures increase emissions from the forest floor. Since 2021 Finnish mineral soils have also turned into an emission source. 

Experts also cited declining growth and increased deforestation as other contributing reasons.

The process is similar in other neighbouring countries. For example, research published in Global Biochemical Cycles in September 2024 describes a worrying trend for the whole of Europe.

“The weakening of the land carbon sink is caused by an accelerated increase in the emission of carbon dioxide from the biosphere, which is not counterbalanced by a concomitant increase in carbon dioxide uptake by vegetation, as in the decades before”, Ronny Lauerwald, from the Paris-Saclay University in France, is quoted as saying.

“In particular, forest disturbances have increased in the last thirty years. In contrast, the carbon dioxide uptake by vegetation has stagnated since the 2000s.”