Controlled burning of natural environments ‘could help offset carbon emissions’

Prescribed burns can lock in the greenhouse gas in temperate forests, savannahs and grasslands, research finds

Thursday 23 December 2021 16:12 GMT

Controlled burning of natural environments such as forests could help save the planet, according to new research (Getty Images)

Controlled burning of natural environments such as forests could help save the planet, according to new research.

Setting natural environments alight can increase carbon storage in the soil, and prescribed burns actually lock in the greenhouse gas in temperate forests, savannahs and grasslands.

Dr Adam Pellegrini, lead author of a study by the University of Cambridge, believes the method could therefore be used to maximise carbon storage in the soil.

He said: “Using controlled burns in forests to mitigate future wildfire severity is a relatively well-known process.

“But we have found that in ecosystems including temperate forests, savannahs and grasslands, fire can stabilise or even increase soil carbon.”

He added: “Most of the fires in natural ecosystems around the globe are controlled burns, so we should see this as an opportunity.

“Humans are manipulating a process, so we may as well figure out how to manipulate it to maximise carbon storage in the soil.”

The finding in the journal Nature Geoscience points to a better method of manipulating the world’s natural capacity for carbon capture, and it is thought it could boost ecosystems.

The study found fires can cause transformations within soils, which can offset immediate losses and may even stabilise ecosystem carbon.

Fire creates charcoal, which is very resistant to decomposition, and forms “aggregates”. The physical clumps of soil protect carbon-rich organic matter at the centre.

Fire can also increase the amount of carbon bound tightly to minerals in the soil.

Dr Pellegrini said: “Ecosystems can store huge amounts of carbon when the frequency and intensity of fires is just right.

“It is all about the balance of carbon going into soils from dead plant biomass, and carbon going out of soils from decomposition, erosion, and leaching.”

Frequent or intense fires in dense forests burn all the dead plant material that would otherwise decompose and release carbon into the soil.

They can also destabilise the soil, breaking off carbon-based organic matter from minerals and killing soil bacteria and fungi.

Without fire, soil carbon is recycled – organic matter from plants is consumed by microbes and released as carbon dioxide or methane.

But infrequent, cooler fires can increase the retention of soil carbon through the formation of charcoal and soil aggregates that protect from decomposition.

The scientists say ecosystems can also be managed to increase the amount of carbon stored in their soils.

Much of the carbon in grasslands is stored below ground, in the roots of the plants.

Controlled burning, which helps encourage grass growth, can increase root biomass and therefore increase the amount of carbon stored.

Dr Pellegrini said: “In considering how ecosystems should be managed to capture and store carbon from the atmosphere, fire is often seen as a bad thing.

“We hope this new study will show that when managed properly, fire can also be good – both for maintaining biodiversity and for carbon storage.”

The study focused on carbon stored in topsoils, defined as those less than a foot deep.

More carbon is stored in the world’s soil than in the global vegetation and the atmosphere combined.

Natural fires occur in most ecosystems worldwide, making fire an important process in global carbon cycling.

The national parks of the Sierra Nevada Mountains have been using prescribed fire to thin forests for over a decade.

Dr Pellegrini said: “Given 70 percent of global topsoil carbon is in fire-prone regions, using fire to promote soil organic matter stability may be an important nature-based climate solution to increase storage.”