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Savanna carbon emissions improved by dead reckoning

By Mike McRae

December 19, 2016

smokey fire through bush
A low intensity savanna fire burning late in the afternoon.

For millennia, cultures indigenous to Northern Australia have used fire to manage and maintain access to the habitat’s bountiful resources. Today, the burning of tropical savanna includes a rather different purpose – the managing of greenhouse gas emissions. The method we use to calculate emissions from savanna fires has required a rethink, however, as new research shines a light on the carbon locked up as dead vegetation.

On first impression, it seems counter intuitive. Combustion releases greenhouse gases, so how would setting fire to a grassland reduce carbon emissions? In 2007, the West Arnhem Land Fire Abatement Project – a partnership between traditional owners and rangers, Darwin Liquefied Natural Gas, the Northern Territory Government, and the Northern Land Council – received the first Australian Museum Eureka Prize for Innovative Solutions to Climate Change. The award acknowledged lighting smaller fires early in the August to December dry season prevented larger, hotter fires from spreading later, thereby reducing greenhouse gas emissions.

fire through low scrub
Tropical savannas dominate the north of the Australian continent and are subject to frequent fires.

Less intense savanna fires still contribute a net amount of carbon, however, which needs to be accounted for. CSIRO’s Garry Cook explains how Australia has been calculating emission of greenhouse gases from these fires based on guidelines published by the Intergovernmental Panel on Climate Change in 1996.

“Under those accounting rules only emissions of methane and nitrous oxide were assessed,” Cook says. “This is because the complexities of full carbon accounting in these systems.”

Adding up the methane and nitrous oxide emissions is a matter of estimating the amount of fuel that goes up in smoke each year and multiplying it by numerous factors for each emission. The problem is that these calculations don’t include the carbon stored in dead organic material that accumulates within these ecosystems. More recent guidelines from the IPCC provide a framework to factor in the carbon in dead organic matter. Research conducted by Cook and his team has provided the means to work out the amounts of carbon in dead wood and leaf litter and how they change over time.

Recalculating carbon

In a paper published recently in the International Journal of Wildland Fire, the researchers showed the carbon locked away in dead vegetation each year was about 3.5 times the annual reduction in methane and nitrous oxide emissions from controlled burning. According to Cook, they did this by mathematically modelling the annual inputs of dead wood from trees, the annual decomposition of wood and the amounts consumed by fires.

“By reducing the overall fire frequency and particularly of uncontrolled and intense late dry season fires, the emissions will be reduced and also more carbon will be stored in the landscape, particularly in the form of unburnt logs,” says Cook. Given that the contributions of that stored carbon haven’t been factored into previous greenhouse gas emissions calculations, carbon accounts of fire-managed savannas have been significantly underestimated.

man in protective orange suit near burning log
CSIRO scientist Mick Meyer collecting gases to analyse the composition of smoke from burning logs in northern Australian savannas.

What’s more, understanding of the important role fire plays in maintaining a balance between grass and trees is vital in supporting the need for effective reduction of greenhouse gas emissions from fire. Cook emphasises the need for accurate information. “In many parts of the world, savannas are coming under pressure for carbon projects that aim to exclude fires completely and replace the open grassy woodland structure of savannas with a closed and often exotic forest. This would be a bad outcome for many regions.”

Already, projects to reduce savanna burning emissions have been registered across 27 per cent of northern Australia. Having the right models to accurately determine the balance of emissions and stored carbon is therefore becoming increasingly important. “This new methodology will provide additional incentive for improving land management in this important part of Australia.”

An anthropogenic landscape

The Warddekken Indigenous Protected Area is one such stretch of country being managed by Indigenous rangers through traditional controlled burning methods. Consisting of nearly 1.4 million hectares of gorges, grassland and forest, it carries significant natural value in its sandstone heathlands and unique ecology.

It is also culturally significant to the local Manmoyi, Kabulwarnamyo and Kamarkarwan communities.

From the late nineteenth century, however, those lawns went ‘unmown’ as communities were forced to live away from their traditional country, and knowledge was lost. For decades the savannas went untended and wildfires burned unchecked, ravaging the landscape and releasing significant amounts of greenhouse gases. Today, ranger programs are helping to restore the balance.

Warddekken Land Management employs more than 120 locals as rangers, operates the Kabulwarnamyo primary school, and is a central partner in the West Arnhem Land Fire Abatement Project. For them, finding there is more carbon locked up than previously thought can only further demonstrate the benefits of traditional burning practices in Australia’s tropics. Savanna burning is supported by the federal government’s Emissions Reduction Fund (ERF), which purchases carbon credits based on the reduction of greenhouse gases.

Taking credit for dead carbon

Currently, Australian carbon credit units are issued solely on the basis of estimated reductions in methane and nitrous oxide gases caused by burning earlier in the dry season. A new draft ERF method proposes to take into account carbon stored in dead vegetative materials in addition to accounting for emissions reductions.

The new draft methods propose to allow land managers of existing and new savanna fire management projects to choose whether to establish or continue to be an emissions avoidance project, or become a sequestration project. Both methods have been updated to incorporate the latest science.

Given estimates that carbon credits issued for the carbon stored in debris could be up to three times that for avoided emissions, describing fire management projects as a sequestration method could be a welcome bonus for groups like Warddekken Land Management.

Yet there is a catch. Although there are more available carbon credits under a sequestration method, there are additional requirements to show how their land management stores additional carbon. Nonetheless, some extra paperwork is a small price to pay for a potential reward to keep our savannas healthy and bury more carbon underground.

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