In recent years, several major wildfires have erupted in the Northern Hemisphere, and many are warning that large emissions of carbon dioxide from burning forests are accelerating global warming.
In a study published in the journal Science, US climate researchers at the University of Arizona showed that some long-term fires could increase the carbon dioxide uptake of developing forests, outweighing emissions from fire. Growing forests can over-offset carbon dioxide emissions.
But this applies only to forests that, after large wildfires, transform from coniferous forests to predominance of deciduous trees.
New species prefer to absorb carbon dioxide
Deciduous trees have a deeper root system and thus absorb more nutrients from the soil. It grows faster and at the same time absorbs more carbon, says forest researcher Anders Lindroth of Lund University.
Researchers have studied forest fires in North America for 15 years. Above all, it is the strong forest fires, where the fires are ignited by roots and vegetation, that alter the composition of the forest species. Fast-growing deciduous trees dominate the forest that grows after the ravages of a fire, which benefits carbon dioxide absorption.
Deciduous trees are fast growing
The effect also depends on natural regrowth, as it favors the return of fast-growing deciduous trees.
– In the event of a strong fire that burns a lot of organic matter in the soil, then the seeds of deciduous trees will be activated, and these trees become dominant. And Anders Lindroth says it is very effective at absorbing more carbon.
The study shows that the final bill for forest carbon balance may end up on the positive side, as a growing forest can absorb more carbon dioxide than was released due to fire. Restored forests can also restrict carbon for a longer period of time, providing a further stabilizing effect on global warming.
But this only applies if the regrowth of the forest is left to fend for itself and leads to a shift from a coniferous to a deciduous forest. In cases where the forest is replanted by fir and pine, the positive effect is absent. It takes a long time before fire emissions are compensated for through plantation.
Compensation for fire emissions takes many years, but new deciduous forests are better than new coniferous forests. Anders Lindroth says preventing future wildfires in forests in the Northern Hemisphere is an important component of the fight against global warming.
Correction: The title has changed