Are wildfires locking up carbon?

Researchers Dr Cristina Santín and Professor Stefan Doerr from the Geography Department have led a study that shows wildfires compensate for the amount of carbon they release into the atmosphere by generating a stable carbon store that lasts for centuries.

Wildfires1Prof. Doerr explains: “Wildfires are seen as major environmental threats, emitting large amounts of carbon into the atmosphere. However, although this is often not considered, they become essentially net zero-emission events when the burnt vegetation recovers fully after the fire (so the carbon that was lost is stored again in the new vegetation). Of course this recovery is not immediate; it may take from a couple of years (grassland fires) to several decades (forest fires)”.

However, Dr Santín points out, carbon emissions are only one side of the ‘fire story’: “fire also transforms part of the burnt vegetation into charcoal. Charcoal is very resistant to degradation and, therefore, it can act as a sink of carbon. So, when we look at the carbon balance from wildfires we need to account not only for the carbon that has been emitted, but also for the carbon that remains in the environment as charcoal”. 

Their work has proven that charcoal production by wildfire is currently underestimated, and, in the case of the boreal forest fire examined in their first published study, charcoal production is equivalent to 50% of the carbon that is emitted into the atmosphere.

 Wildfires2“That underestimation is mainly methodological and does not only apply to the boreal forest but to almost every fire-prone ecosystem, what suggests that if you carry out a complete quantification somewhere else you will find more charcoal than you may think. So, if charcoal production is quantitatively important worldwide, it needs to be accounted for in global carbon budgets”. 

Prof. Doerr also clarifies that when fire is taken beyond its natural role it may have negative implications. “We should not forget that there are some fires that cause a permanent degradation of the ecosystem.  In these fires, charcoal still acts as a carbon sink, but this sink will be clearly more than offset by the permanent loss of vegetation.  These ‘degradation’ fires, are mainly human driven so, here we face once more the fact that humans are the ones throwing nature off balance”. 

The first results of their investigation, carried out in collaboration with Canadian Government organisations, have just been published, in Global Change Biology (http://onlinelibrary.wiley.com/journal/10.1111/(ISSN)1365-2486) and have already stimulated international scientific debate (http://onlinelibrary.wiley.com/doi/10.1111/gcb.12836/epdf; http://onlinelibrary.wiley.com/doi/10.1111/gcb.12892/abstract ). 

Prof. Doerr remarked “we have shown that charcoal production from wildfires could represent a substantial and currently unaccounted sink in the global carbon cycle. The most urgent task is to fill this gap by obtaining reliable data for a range of globally important ecosystems and types of fires”.

The continuity of this research has been secured via a Leverhulme Trust Foundation Grant awarded to Prof. Doerr, enabling the team to continue their investigation using the experimental forest wildfires in The Northwest Territories of Canada over the next four summer campaigns.