Study finds fire severity, not climate, most affects megafire recovery

Forests recovering more slowly from large wildfires since 2010

Forests are taking longer to recover after large-scale wildfires, according to research published in Nature Ecology & Evolution and reported by Carbon Brief.

The study examined 3,281 large-scale fires (exceeding 10 square kilometres) between 2001 and 2021 and found that fire severity has increased notably since 2010, particularly in boreal forests and arid regions.

Carbon Brief reported that fewer than one-third of the forests studied had returned to pre-fire conditions within seven years, with fire severity having a more negative impact on forest recovery than post-fire climate conditions.

Boreal forests and dry climates among worst affected

The researchers identified western North America, northern Siberia, and south-eastern Australia as areas with some of the most severe changes.

According to Professor Ziyue Chen from Beijing Normal University, fire severity has “significantly increased” since 2001, with evergreen needleleaf forests especially vulnerable.

Chen said: “More concerningly, the adverse impacts of changing environmental conditions – especially rising temperatures and soil moisture deficits – on forest recovery are intensifying, necessitating urgent attention.”

The study found that boreal forests had the lowest recovery rates, with many still showing signs of damage years after fire events.

Fire severity has greater impact than climate on recovery

Using machine learning, the study assessed the influence of various factors on recovery.

Fire severity was found to be the strongest determinant of recovery time, surpassing climate-related factors such as temperature and precipitation.

Professor Chaoyang Wu from the Chinese Academy of Sciences said: “While numerous studies report beneficial effects of warming on vegetation greenness and productivity, our results suggest these benefits may diminish or reverse as temperatures surpass optimal ranges for photosynthesis.”

Chen added that while climate still plays a role, the scale of the fires was more influential in determining how forests responded after a fire.

Slower regrowth threatens carbon storage and ecosystem stability

The study reported that average recovery time increased by 8% for vegetation density, 11% for canopy structure and 27% for productivity metrics since 2010.

According to Carbon Brief, forest stagnation – where recovery slows after initial regrowth – rose from 23% to 26% post-2010.

Professor Guido van der Werf of Wageningen University, who was not involved in the research, told Carbon Brief: “It is a neat paper that quantifies something that is expected, but not previously reported on such a large scale: with increased fire activity in forests there seems to be slower recovery.”

Dr Bernardo Flores from the Federal University of Santa Catarina also told Carbon Brief the results align with previous findings, saying: “If global forest flammability is rising, this will also affect tropical forests during drier years, as we saw in 2023–24 in the Amazon.”

Megafire recovery takes longer as fire severity increases worldwide: Summary

Forests worldwide are recovering more slowly from large-scale wildfires since 2010.

The study was published in Nature Ecology & Evolution and reported by Carbon Brief.

It analysed 3,281 large wildfires from 2001 to 2021.

Fire severity increased after 2010, especially in boreal and arid regions.

Less than one-third of forests recovered fully within seven years.

Recovery was slower in dry regions and evergreen needleleaf forests.

Fire severity had more influence on recovery than climate change.

Average recovery times rose by 8% to 27% across various indicators.

Forest stagnation rates increased from 23% to 26% after 2010.

Boreal forests had the lowest recovery rates.

Humid tropical forests showed the highest recovery success.

Researchers used machine learning to isolate fire and climate effects.

Findings suggest changes in fire scale must be included in future models.

Experts warned slower recovery may affect forests’ carbon storage roles.