Deep soils store up to five times more carbon than is commonly reported, a new study by Murdoch University and Cranfield University in the UK has found.

Soil locks in greenhouse gases by storing carbon, making it a crucial player in the fight against global warming. Greenhouse gases are released when soils are exposed to air by farming, peat drainage and deforestation.

Current estimates of soil organic carbon are based largely on measurements to depths of 30 cm. This approach has evolved in North America and Europe, where soil is generally more shallow.

However, many plant species have roots extending many metres deep, suggesting there is also carbon stored at such depth and inspiring researchers to explore the storage potential of deeper soils in older landscapes such as the Amazon or Australia. Researchers in the Amazon had previously sampled soils to 8 m.

The researchers took soil measurements from samples taken to almost 40 metres deep at a range of sites in south-western Australia.

They found that small amounts of carbon were present throughout the soils all the way to the bedrock, and that deep soils store up to five times more carbon than is normally reported.

“This finding may have major implications for estimates of global carbon storage and modelling of the potential global impacts of climate change and land-use change on carbon cycles,” the researchers said in their paper, which was published in the journal Plant and Soil.

Lead researcher Professor Richard Harper, an expert in water management and sustainability at Murdoch University said the findings extend our concept of the amounts and potential of carbon stored in soils.

“This carbon has been previously overlooked, and this opens up several lines of inquiry – for example, what happens to this carbon with land use change such as deforestation and reforestation?” Professor Harper said.

“There is likely more carbon stored in the world’s soils than previously considered. What will happen to this carbon – that is, will it be released as a result of either land-use change or climate change – is unknown. This is what we are working on now,” he said.

Landmark study

Professor of Horticulture and Viticulture at the University of Melbourne, Snow Barlow, said the study highlights the significant impact of land use change on global carbon cycles.

“This paper is a timely reminder of the impacts of land use change, as this carbon has clearly originated in the earlier forested era of these landscapes,” said Professor Barlow, adding that Australia’s position on the UN Kyoto Protocol climate change agreement was strongly based on the significance of land use change through decreasing land clearing.

“It is also a strong reminder of how much carbon is actually stored in soils, particularly deep soils, and that even Australia has deep soils that contain significant carbon at moderate rainfalls.”

Dr Robert Edis, a soil scientist from the University of Melbourne said the study was “robustly and rigorously executed and then elegantly interpreted”, but added that the importance of deep soil carbon for climate change, “hinges on how stable the carbon is, and will determine if the study is just interesting or pivotal.”

Dr Edis said the study was a “landmark quantification of a pool of carbon only qualitatively suspected.”

Andrea Koch, project manager of the Soil Carbon Initiative at the University of Sydney said the study highlights how much we have underestimated the potential for soils to act as a critical sink for carbon.

“As a society, we are pretty focused on what we can get from the top 30cm of the soil profile, and the mineral and energy resources that are deep below the surface, but the soil in between the deeper soil is a frontier that is yet to be understood. Managing and maintaining soil carbon is fundamental to food and water security, biodiversity and energy security, as well as climate regulation, so if we can work out ways to manage soil carbon at depth that can only be a good thing,” Ms Koch said.

“Finding ways to manage and account for soil carbon at depth will not only require new soil management practices and technologies, it will also need to be met with public policies that support and encourage these efforts,” she said.

Bad weather does a lot more than spoil barbecues. Last year’s floods in the UK caused £400m-worth of damage, while this summer’s floods in central Europe could lead to insurance claims for as much as €6bn (£5.1bn); at the other extreme, last year’s droughts in the US Midwest’s corn belt caused around $20bn (£13bn) of damage to agricultural crops.

There is still not 100% agreement in the industry as to whether or not man-made climate change exists but arguing the point rather misses the bigger issue, said Laurence Baxter, the head of policy and research at the Chartered Insurance Institute, the professional body.

“I have seen the debate waged over the last few years – individuals in and out of the industry – and in that they miss the whole point, which is that extreme weather events are on the rise and a number of weather-related records have been broken in the last few years. The climate is changing and as the sector responsible for managing risk and how it is mitigated… the insurance industry does play a big part.”

The industry is starting to recognise this. The CII incorporates the issue into its qualifications and continuing professional development resources for its members, while a number of insurers got together six years ago to set up the ClimateWise leadership group to work together investigating the issue.

The group’s members have recognised that the number of extreme weather events and other climate-linked changes have significant implications for their businesses, said Katharine Thoday, head of the ClimateWise secretariat at the University of Cambridge Programme for Sustainability Leadership. The group has set up six principles, including informing public policy, incorporating climate change into members’ investment strategies and reducing the environmental impacts of their business.

One of the underlying challenges is that climate change is still far from fully understood, meaning that companies are always dealing with uncertainty, said Dr Stefan Straub, Munich Re’s spokesman on climate change and renewable energy. “No one can say ‘that’s the last piece of the puzzle’. The research is still going on. We still don’t know enough, which makes it difficult to assess the risks in the right way.” It funds or is otherwise involved in a large number of research initiatives to help improve understanding of the issues involved, as well as supporting the development of renewable energy technology.

Knowledge may not yet be complete but it is improving, said Jon Williams, a partner at PricewaterhouseCoopers, which reviews insurers’ performance against the ClimateWise principles. The industry is making the most progress in research and development and risk modelling, engagement with policymakers, and product innovation, he said. “For example, in the UK 10 years ago flood-risk modelling was a high-level crude postcode lottery,” he said. “Now it’s sub-postcode mapping of how water will flow across terrain.”

Companies are also starting to create products that try to change consumer behaviour, said Williams. Aviva’s “pay as you drive” policy, which means heavy car users pay higher premiums than those who drive for short distances, is one example; another is the way in which insurers make assets more resilient to risk after they have had to pay out. “So in a flood-risk area, expect to have your power points reinstalled 24 inches up so that if it floods again it won’t take out all your electrics.”

But the picture is not all positive. For a start, there is still much more that could be done to develop new products that help mitigate risk, said Williams. “And another area where relatively little has been done is understanding the risks of climate change to those more exposed to them, especially in developing countries.” This is becoming increasingly important as insurers look to these markets for new opportunities for growth now that the UK market is saturated – Williams’ pun.

“What that does is take them into markets where governments are typically less able to adapt to climate change so risks are higher, and much higher for insurers,” he said.

Even insurers with no direct involvement in developing markets need to understand the issues there, he said. “About a third of premiums insured in this market come from overseas so they are already exposed to overseas. Secondly, the world is pretty connected and the biggest threat to the UK from climate change is through the supply chain, particularly through food security.” A British insurer that offers business continuity insurance to a company based in the UK could easily be exposed to climate change risks down the line, for example if a drought in Kenya wiped out a major supplier’s crop.

He also believes that insurers need to think harder about what they can do with their asset portfolios. This is a tricky area, said Thoday. “The outside perception is that, because insurers from the underwriting side have been thinking about these issues… there’s a strong sense that they should be applying it to their investments,” she said. “In reality as a business those two things are very separate. For all kinds of regulatory reasons you don’t share your risk analysis from the underwriting side with the investment decision side.” That said, this is a question that’s starting to get on the agenda of the investment side, she added.

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