̽��ֱ�� of Cambridge - Adam Pellegrini

UK peatland fires are supercharging carbon emissions as climate change causes hotter, drier summers

jg533 — Fri, 21 Feb 2025 07:00:52 +0000

More fires, taking hold over more months of the year, are causing more carbon to be released into the atmosphere as carbon dioxide.

Fires on peatlands, which are carbon-rich, can almost double global fire-driven carbon emissions. Researchers found that despite accounting for only a quarter of the total UK land area that burns each year, dwarfed by moor and heathland, wildfires that burn peat have caused up to 90% of annual UK fire-driven carbon emissions since 2001 – with emissions spikes in particularly dry years.

Peat only burns when it’s hot and dry enough - conditions that are occurring more often with climate change. ̽��ֱ��peatlands of Saddleworth Moor in the Peak District, and Flow Country in northern Scotland, have both been affected by huge wildfires in recent years.

Unlike heather moorland which takes up to twenty years to regrow after a fire, burnt peat can take centuries to reaccumulate. ̽��ֱ��loss of this valuable carbon store makes the increasing wildfire frequency on peatlands a real cause for concern.

̽��ֱ��researchers also calculated that carbon emissions from fires on UK peatland are likely to rise by at least 60% if the planet warms by 2^oC.

̽��ֱ��findings, which are broadly relevant to peatlands in temperate climates, are published today in the journal 'Environmental Research Letters'.

“We found that peatland fires are responsible for a disproportionately large amount of the carbon emissions caused by UK wildfires, which we project will increase even more with climate change,” said Dr Adam Pellegrini in the ̽��ֱ�� of Cambridge’s Department of Plant Sciences, senior author of the study.

He added: “Peatland reaccumulates lost carbon so slowly as it recovers after a wildfire that this process is limited for climate change mitigation. We need to focus on preventing that peat from burning in the first place, by re-wetting peatlands.”

"We found that in dry years, peatland wildfires were able to burn into the peat and release significant quantities of carbon into the atmosphere. In particularly dry years this contributed up to 90% of the total wildfire-driven carbon emissions from the UK," said Dr Sarah Baker, lead author of the study which she conducted while at the ̽��ֱ�� of Cambridge. Baker is now based at the ̽��ֱ�� of Exeter.

̽��ֱ��researchers found that the UK’s ‘fire season’ - when fires occur on natural land - has lengthened dramatically since 2011, from between one and four months in the years 2011-2016 to between six and nine months in the years 2017-2021. ̽��ֱ��change is particularly marked in Scotland, where almost half of all UK fires occur.

Nine percent of the UK is covered by peatland, which in a healthy condition removes over three million tonnes of carbon dioxide from the atmosphere per year.

̽��ֱ��researchers estimate 800,000 tonnes of carbon were emitted from fires on UK peatlands between 2001 and 2021. ̽��ֱ��2018 Saddleworth Moor fire emitted 24,000 tonnes of carbon, and the 2019 Flow Country fire emitted 96,000 tonnes of carbon from burning peat.

To get their results, the researchers mapped all UK wildfires over a period of 20 years – assessing where they burn, whether peat burned, how much carbon they emit, and how climate change is affecting fires. This involved combining data on fire locations, vegetation type and carbon content, soil moisture, and peat depth. Using UK Met Office model outputs, the team also used simulated climate conditions to project how wildfires in the UK could change in the future.

̽��ֱ��study only considered land where wildfires have occurred in the past, and did not consider the future increases in burned area that are likely to occur with hotter, drier UK summers.

An average of 5,600 hectares of moor and heathland burns across the UK each year, compared to 2,500 hectares of peatland.

“Buffering the UK’s peatlands against really hot, dry summers is a great way to reduce carbon emissions as part of our goal to reach net zero. Humans are capable of incredible things when we’re incentivised to do them,” said Pellegrini.

̽��ֱ��research was funded by Wellcome, the Isaac Newton Trust and UKRI.

Reference: Baker, S J et al: ‘Spikes in UK wildfire emissions driven by peatland fires in dry years.’ February 2025, Environmental Research Letters. DOI: 10.1088/1748-9326/adafc6.

A new study led by the ̽��ֱ�� of Cambridge has revealed that as our springs and summers get hotter and drier, the UK wildfire season is being stretched and intensified.

Peatland fires are responsible for a disproportionately large amount of the carbon emissions caused by UK wildfires, which we project will increase even more with climate change

Adam Pellegrini

Sarah Baker

Fire on UK moorland

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Drier savannas and grasslands store more climate-buffering carbon than previously thought

jg533 — Sat, 30 Sep 2023 16:17:53 +0000

̽��ֱ��study estimates that soils in savanna-grassland regions worldwide have gained 640 million metric tons of stored carbon over the past two decades.

This is because over the last 20 years, fire suppression has led to smaller wildfires, and less burned area in drier savannas and grasslands.

When soil microbes break down fallen leaves, dead plant matter and roots, the carbon in this plant biomass is released and can associate with minerals in the soil to become very stable. But the energy of an intense fire can burn it back off, releasing carbon dioxide into the atmosphere.

Fires are being suppressed because of population expansion, and landscape fragmentation caused by the introduction of roads, croplands and pastures in savannas and grasslands.

̽��ֱ��study, published today in the journal Nature Climate Change, is based on a reanalysis of datasets from 53 long-term fire-manipulation experiments worldwide, as well as field-sampling at six of those sites.

“We found that the potential - at very high fire frequencies - to release soil carbon into the atmosphere as carbon dioxide is greatest in dry areas. ̽��ֱ��potential to store carbon in soil when fires are less frequent is also the greatest in these dry areas,” said Dr Adam Pellegrini in the Department of Plant Sciences at the ̽��ֱ�� of Cambridge, and lead author of the study.

̽��ֱ��reduction in the size and frequency of wildfires in dryland savannas has led to an estimated 23% increase in carbon stored in topsoil. This increase was not foreseen by most of the state-of-the-art ecosystem models used by climate researchers. As a result, the researchers say, the climate-buffering impacts of dryland savannas are likely to have been underestimated.

Soil contains at least three times more organic carbon than the atmosphere or terrestrial plants, making it an important global carbon pool.

"Our findings show that because drier savannas are more sensitive to changes in fires, the decreases in burned area in those ecosystems has resulted in soils storing more carbon than they are releasing,” said Pellegrini.

He added: “Many of the ecosystem models that are used in simulating the effects of global change on carbon cycling are unlikely to have captured these dynamics."

̽��ֱ��study involved twenty researchers from institutions around the globe, who looked at recent changes in burned area and fire frequency in savannas, other grasslands, seasonal woodlands and forests.

Across 888,000 square miles (2.3 million square kilometers) of dryland savanna-grasslands, where fire frequency and burned area declined over the past two decades, soil carbon rose by an estimated 23%.

But in more humid savanna-grassland regions covering 533,000 square miles (1.38 million square kilometers), more frequent wildfires and increased burned area resulted in an estimated 25% loss in soil carbon over the past two decades.

̽��ֱ��net change during that time was a gain of 0.64 petagrams, or 640 million metric tons, of soil carbon.

“In the past couple of decades, global savannas and grasslands have slowed climate warming more than they have accelerated it, despite fires. But there is absolutely no guarantee that this will continue in the future,” said Peter Reich, Director of the Institute for Global Change Biology at the ̽��ֱ�� of Michigan, who was also involved in the study.

“No single region – from the Amazon rainforest, to the US Great Plains grasslands to Canada’s boreal forest - can alone store sufficient carbon to make a large contribution to slowing climate change. But together, they can,” said Pellegrini.

He added: “There are several savanna and grassland regions where soil carbon-credit projects are being developed, so understanding their capacity to sequester carbon is relevant to those regions.”

This research was funded by the U.S. Department of Agriculture, United Kingdom Research and Innovation (UKRI), the Gordon and Betty Moore Foundation, and the US Department of Energy.

Learn more about Adam Pellegrini’s work.

Reference: Pellegrini, A.F.A, et al.: 'Soil carbon storage capacity of drylands under altered fire regimes.’ Nature Climate Change, October 2023. DOI: 10.1038/s41558-023-01800-7

Adapted from a press release by the ̽��ֱ�� of Michigan.

Savannas and grasslands in drier climates around the world store more carbon than scientists previously thought and are helping to slow the rate of climate warming, according to a new study.

Because drier savannas are more sensitive to changes in fires, the decreases in burned area in those ecosystems has resulted in soils storing more carbon than they are releasing

Adam Pellegrini

Fire in oak savannah

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

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Controlled burning of natural environments could help offset our carbon emissions

jg533 — Thu, 23 Dec 2021 16:19:18 +0000

̽��ֱ��finding points to a new method of manipulating the world’s natural capacity for carbon capture and storage, which can also help to maintain natural ecosystem processes. ̽��ֱ��results are published today in the journal Nature Geoscience.

“Using controlled burns in forests to mitigate future wildfire severity is a relatively well-known process. But we’ve found that in ecosystems including temperate forests, savannahs and grasslands, fire can stabilise or even increase soil carbon,” said Dr Adam Pellegrini in the ̽��ֱ�� of Cambridge’s Department of Plant Sciences, first author of the report.

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.”

Fire burns plant matter and organic layers within the soil, and in severe wildfires this leads to erosion and leaching of carbon. It can take years or even decades for lost soil carbon to re-accumulate. But the researchers say that fires can also cause other transformations within soils that can offset these immediate carbon losses, and may stabilise ecosystem carbon.

Fire stabilises carbon within the soil in several ways. It creates charcoal, which is very resistant to decomposition, and forms ‘aggregates’ – physical clumps of soil that can protect carbon-rich organic matter at the centre. Fire can also increase the amount of carbon bound tightly to minerals in the soil.

“Ecosystems can store huge amounts of carbon when the frequency and intensity of fires is just right. It’s all about the balance of carbon going into soils from dead plant biomass, and carbon going out of soils from decomposition, erosion, and leaching,” said Pellegrini.

When fires are too frequent or intense - as is often the case in densely planted forests - they burn all the dead plant material that would otherwise decompose and release carbon into the soil. High-intensity fires 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.

̽��ֱ��scientists say that 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.

“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,” said Pellegrini.

̽��ֱ��study focused on carbon stored in topsoils, defined as those less than 30cm 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.

This research was funded by the Gatsby Charitable Foundation.

Reference
Pellegrini, AFA.et al: ‘Fire effects on the persistence of soil organic matter and long-term carbon storage’, Nature Geoscience, December 2021. DOI 10.1038/s41561-021-00867-1

Forests' long-term capacity to store carbon is dropping in regions with extreme annual fires

jg533 — Thu, 25 Feb 2021 16:01:42 +0000

Savannah ecosystems, and regions with extreme wet or dry seasons were found to be the most sensitive to changes in fire frequency. Trees in regions with moderate climate are more resistant. Repeated fires also cause less damage to tree species with protective traits like thicker bark.

These effects only emerge over the course of several decades: the effect of a single fire is very different from repeated burning over time. ̽��ֱ��study found that after 50 years, regions with the most extreme annual fires had 72% lower wood area - a surrogate for biomass - with 63% fewer individual trees than in regions that never burned. Such changes to the tree community can reduce the forest’s long-term ability to store carbon, but may buffer the effect of future fires.

“Planting trees in areas where trees grow rapidly is widely promoted as a way to mitigate climate change. But to be sustainable, plans must consider the possibility of changes in fire frequency and intensity over the longer term,” said Dr Adam Pellegrini in the ̽��ֱ�� of Cambridge’s Department of Plant Sciences, first author of the paper.

He added: “Our study shows that although wetter regions are better for tree growth, they’re also more vulnerable to fire. That will influence the areas we should manage to try and mitigate climate change.”

Past studies have found that frequent fires reduce levels of nutrients - including nitrogen - in the soil. ̽��ֱ��new study demonstrates that this can favour slower-growing tree species that have adaptations to help them survive with less nutrients. But these tree species also slow down nutrient cycling in the soil - they hold onto what they have. This can limit the recovery of the forest as a whole by reducing the nutrients available for plant growth after an intense fire.

Wildfires are playing an increasingly important role in global carbon emissions. Fire burns five percent of the Earth’s surface every year, releasing carbon dioxide into the atmosphere equivalent to 20% of our annual fossil fuel emissions.

In the past, the majority of carbon released by wildfires was recaptured as ecosystems regenerated. But the more frequent fires of recent years, driven by changes in climate and land use, don’t always allow time for this.

“As fire frequency and intensity increases because of climate change, the structure and functioning of forest ecosystems are going to change in so many ways because of changes in tree composition,” said Pellegrini.

He added: “More fire-tolerant tree species are generally slower growing, reducing the productivity of the forest. As climate change causes wildfires to become more intense and droughts more severe, it could hamper the ability of forests to recover - reducing their capacity for carbon storage.”

̽��ֱ��study is the largest of its type ever to be undertaken. Researchers analysed data from a global network of 374 plots distributed across 29 sites throughout four continents, where plots have experienced different fire frequencies and intensities for multiple decades.

̽��ֱ��network spans a broad geographical range of ecosystems from African and Australian savannahs and grasslands, to forests in Europe and North America. These are all ecosystems that experience natural burning, or would do if humans weren’t suppressing fires.

This research was funded by the USDA National Institute of Food and Agriculture, and the Gordon and Betty Moore Foundation.

Reference

Pellegrini, A.F.A. et al: ‘Decadal changes in fire frequencies shift tree communities and functional traits.’ Nature Ecology & Evolution, February 2021. DOI: 10.1038/s41559-021-01401-7

Fire: ̽��ֱ��Great Manipulator

jg533 — Mon, 14 Dec 2020 08:43:58 +0000

Climate change is driving more frequent and intense wildfires, damaging ecosystems and causing major carbon emissions. A Cambridge researcher is figuring out how to give nature a helping hand.