Map: how soil carbon may shape the future of farming

A new map of Irish soils’ potential to release or store carbon could determine which farming activities and other land uses may be incentivised or discouraged in the coming years to meet climate change targets.

At last week’s COP22 global climate summit in Morocco, Teagasc’s former lead sustainability researcher Prof Rogier Schulte presented the map, which he said resulted from two years of research by multiple scientists. Schulte is now senior scientist in International Agricultural and Environmental Policy at Wageningen Economic Research in the Netherlands, one of the world’s most advanced research centres in the field of climate change.

While efforts to combat climate change have so far focused on curbing greenhouse gas emissions, Schulte said trapping carbon in the soil is a more promising course of action as far as farming is concerned – if conducted through actions targeted to each type of land.

“We measure all the bad emissions that you’re familiar with. They are being accounted for. But we know of course that the land has potential to sequester or offset carbon,” Schulte told delegates in Marrakesh. Countries were not allowed to use this potential when climate targets were set for 2020 because there was no reliable way of measuring it. But offsetting emissions with carbon sequestration is now partly allowed under the European Commission’s proposed new targets for 2030.

This has made storing carbon in the soil an attractive prospect and Schulte told the Irish Farmers Journal that Ireland was one of the first countries to engage in this process.

What you shouldn’t end up with is a single form of soil management

“Our study for Ireland shows that what you shouldn’t end up with is a single form of soil management,” he said. While he acknowledged that this study is “the first part of a long process”, the resulting map identifies six main types of soil on Irish farms.

Main carbon stores

The black areas on the map are peat lands. The main threat to those rich carbon stores was over-grazing by sheep, but the reduction in the national flock in the past two decades has eased the pressure. “Most of the pain has already been taken,” said Schulte, adding that the priority here should be to “maintain what we have”.

Carbon hot spots

The red areas on the map are peat soils that were drained in the past, mostly in the 1960s and 1970s, and are now farmed intensively. In 2014, international scientists revealed the carbon emissions still coming out of these soils to be up to 20 times higher than previously thought. “We were initially freaked out,” Schulte said, as these emissions suddenly jumped to represent half of all Irish agricultural emissions. Thankfully, international accounting rules do not hold the present generation responsible for actions taken that far back. However, proven emissions cuts from these fields can now be used to improve agriculture’s overall balance. “The good news is that they are pin pricks in the landscape,” Schulte said. “If we want to do something about it, we’re dealing at most with hundreds of farms, not thousands.”

Targeted GLAS payments could be used to help farmers raise the water table or reduce fertiliser input and reverse to a more extensive form of farming, the two actions known to reverse emissions from this drained peat land.

“This could be a very cheap, cost-effective opportunity to make a dent in our agricultural emissions,” Schulte said.

Emission-sensitive soils

The yellow areas on the map are heavy soils that could turn red if drained and farmed intensively. “Since the end of milk quotas, there has been an incentive for farmers to drain new wet land. Not all soils respond the same to drainage,” said Schulte. Mineral soils will release very little greenhouse gas, while peaty ones will have high carbon loss. Draining them would increase agricultural emissions substantially.

Priority afforestation land

The green areas on the map are “marginal soils of reduced environmental interest in terms of biodiversity, which are the target soils in terms of forestry,” Schulte said. Ireland has the lowest forest cover in Europe and new forests could store significant amounts of carbon, but scientists say afforestation incentives should be targeted to these areas for maximum efficiency.

Potential unsaturated long-term carbon storage

while all grassland stores carbon in its topsoil, this is very unstable. “It can go up in a puff of smoke very quickly,” said Schulte. By contrast, the blue areas on the map have recently shown a capacity to store carbon in a way that had not been detected before. “In some soils, we found carbon that is very stable and has been there for hundreds or thousands of years. We found that this soil, at deep layer levels, is still unsaturated,” Schulte said. Further research is needed to determine how this could be used to trap even more carbon.

Little sequestration potential

The grey areas on the map show no particular ability to store carbon in the soil. Broadly, they also happen to match the most intensively farmed areas in Ireland. “That’s where we would focus the efficiency story and the carbon navigator,” said Schulte. Improved animal breeding and husbandry methods as well as better grazing and nutrient management are the most cost-effective ways of improving agriculture’s carbon footprint here. By his account, there is so much to be gained from these measures and from better soil management in the areas above that much-hyped expensive technological options such as anaerobic digestors appear less attractive. Schulte insisted that this map was indicative and not yet at a sufficient scale to determine farm-level decisions. Yet he added that further studies should make it possible to classify each individual field into any of the above categories.

There’s no point in trying to convince farmers to do something for the planet unless you put a price tag on it

As climate obligations become more stringent following the global climate agreement signed last year in Paris, this could have a major influence on agricultural policy, from environmental regulations to the distribution of farm payments.

Schulte said that one of the lessons learned from the past few years is that “money talks – there’s no point in trying to convince farmers to do something for the planet unless you put a price tag on it”. According to him, storing carbon in the soil has a direct benefit to tillage farmers in terms of crop performance, while cutting emissions can be linked to increased profit on livestock farms as shown by the carbon navigator. Elsewhere, he said the GLAS model could be used to pay farmers to take appropriate action: “The Government wouldn’t need to create a whole new scheme for carbon management. It would be more efficient to piggyback on existing ones.”

Land value impact

This leaves one question unanswered: the impact of the soil’s carbon-storing potential on the value of land. What if certain holdings became attached to valuable entitlements to produce more, while others saw their value fall because they cannot be drained or fertilised, as has been the case for biodiversity designated land? While Schulte acknowledged that this was not his area of research, he noted that potential avenues to take this into account were open through the ongoing rethink of taxation around land mobility and review of areas of natural constraint.

Each country’s greenhouse gas emission targets are divided between the Emissions Trading System (ETS), which covers large industrial emitters able to account for their emissions individually, and the effort-sharing or non-ETS sector, which accounts for collective emissions from farms, cars, etc. Under EU rules, Ireland must cut its non-ETS emissions by 20% by 2020 compared with 2005. Current European Commission proposals would increase this target to 30% by 2030.

The 2030 proposal includes flexibility, allowing up to 5.6% in Ireland’s non-ETS target to come from the positive effects of storing carbon in soils and trees. As this will be achieved through efforts in the farming sector, Schulte said it would be fair to attribute all the associated gains to agriculture. Farming represents half of Ireland’s non-ETS emissions, which means Irish agriculture could be allowed to use around 10% in carbon storing offsets to justify its own targets.

“That 10% is exactly the difference between our 2020 and our 2030 targets,” he said. By maximising carbon sequestration in the soil, Irish farmers could therefore meet their obligations of the next decade. This is crucial, because our progress in reducing emissions is expected to be cancelled out by increasing agricultural production. “The snag is that we’re well under way to miss our 2020 targets - we must meet them first,” Schulte added.

The indicative map for climate-smart land management above is based on the Soil Information System of Ireland, which provides a 1:250,000 map of soil associations. At this scale, it is not appropriate to delineate individual soil types. Therefore, this indicative map should be used for guidance only and should not be applied at farm scale. This research was funded by Dairy Research Ireland and the Department of Agriculture.

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