Soil: Standing on a Solution to Climate Change

Published by Kate O'Brien on

July 28th, 2017

Ireland could fight climate change without lifting a finger. Well, maybe a green thumb or two. Kate O’Brien explains.

When we look over Ireland’s rich tapestry of green or the purple moor grass and black bog rush of the countries blanket bogs, the last thing we think about is an answer to climate change.

We might think about the burning of fossil fuels and the destruction of peatlands, or the fact that as an agricultural nation Ireland’s total national greenhouse emissions is amongst the highest of any country in the developed world.

But there’s more to this than meets the eye. The answer is in the soil.

Soil has the potential to store between 1.5 and 5.5 billion tonnes of carbon a year globally. According to the Environmental Protection Agency 20 per cent of all agricultural emissions can be offset by improving soil carbon levels.

Farming, organic farming in particular, offers a potential solution to allay the surplus carbon dioxide in the atmosphere by storing carbon in the soil. So too do Ireland’s peatlands, which have been storing carbon since the last ice-age.

Peatlands sequester carbon

Ireland is unique from an international perspective because our small island contains roughly eight per cent of the world’s blanket bogs, which are protected under International and EU legislation.

According to the Irish Peatland Conservation Council (IPCC), intact Irish peatlands are estimated to store 1085 Mega tonnes (Mt) of carbon. This corresponds to 53 per cent of all soil carbon stored in the island of Ireland on just 16 per cent of the land.

By preserving our wetlands we are not only conserving biodiversity, filtering water and reducing the risk of flood, but sequestering unwanted carbon dioxide emissions at the rate of up to 0.7 tonnes per hectare per year.

However, we are draining our bogs at an alarming rate, 47% of Irish peatlands have been lost to turf cutting and industrial peat extraction.  By draining our peatlands the accumulation process is disturbed and huge amounts of carbon dioxide is released.

Some of the largest emissions of carbon dioxide within the EU result from land use change, in particular the drainage of peatlands, amounting to 20 – 40 tonnes of carbon dioxide per hectare per year.

It is no wonder then that President Michael D Higgins highlighted the importance of peatland conservation at Abbeyleix Bog during May’s National Biodiversity Week.

“We now understand the urgency of coming to grips with climate change and we have pledged to take action to drastically reduce our emissions, as part of a global effort,” he said.

“We know that the world’s peatlands, while only covering three per cent of the Earth’s land mass, contain twice the sequestered carbon of all of the world’s forests combined.”

He added that with 20% of Ireland’s land being comprised of peat soils, there is undoubtedly potential to “look at the management of such land as just one contribution to climate change mitigation purposes.”

Yet, according to Tristram Whye, Conservation, Policy and Fundraising Officer at the IPCC, Irish peatlands are “getting worse”.

“Draining peatlands damages their ability to hold carbon,” says Mr Whye as a high water table is required for peatlands to function as carbon sinks. “It is most important to rewet them, as they are the most important terrestrial carbon stores on the planet.”

Organic matters

Soil organic matter (SOM) stores 1,500 billion tonnes of carbon globally, almost three times more carbon than in all above ground biomass including trees, shrubs and grasses. Organic matter is vital for soil fertility, binding soil particles together it traps water and nutrients for plant root systems.

SOM is what gives the top layer of soil its distinctive dark colour. It is the component of soil that consists largely of plant material and animal residues at various stages of decomposition. Organic matter not only removes pollutants from the earth, retains water to prevent flooding and feeds the soil it also contributes to the soils ability to sequester carbon from the atmosphere.

As organic farming practices ensure healthy soil contains 5 per cent organic matter or more, these farms act as carbon sinks. According to the UK Soil Association, a 2012 meta-analysis found that organic farms store on average 0.27 to 0.45 tonnes more carbon in topsoil per hectare per year.

Currently, only two per cent – 72,000 ha of land – of Ireland’s farms are certified organic, with an Organic Farming Action Plan now in place with a target to increase this certified land area to 5 per cent by 2020.

The widespread adoption of sustainable soil management practices in agriculture could help sequester between 50 and 100 million tonnes of carbon per year in European soils.

Other techniques to improve soil health and put carbon back in the soil include planting as many cover crops as possible, using mycorrhizal soil inoculant where possible and reduced tillage.

“Every time we disturb the soil we are releasing CO2,” says Philip Wheal, Horticulturalist at the Organic Centre in Leitrim. “The less you disturb the soil the more you will lock up and store carbon into vegetation and soil”.

Organic matter not only holds carbon but it is used to grow food, hold water and prevent flooding, break down pollutants and prevent erosion.

Unfortunately, soil organic matter levels are currently on the decline on non-organic farmland across Europe. Irish soils have high susceptibility to compaction resulting from the use of heavy machinery and agriculture, nd have been further degraded by artificial chemicals and fertilisers.

Grazing land areas cover vast areas and so collectively can absorb large quantities of carbon if they are well managed – for example by controlled grazing, preventing fires, planting trees, conserving soil and water, restoring eroded and saline land, and reanimating wetlands.

Despite soil being so precious, and unlike other natural resources like water or air, Ireland to date has no incentives to protect soil. Human pressures on soil resources, especially in Europe, have reached a critical limit.

‘People for Soil’ is a European Citizens’ Initiative backed by more than 500 associations, asking the EU for specific regulations to protect soil. Ireland needs 8,250 signatures to reach its target this August.

As well as supporting initiatives to protect our soils, we can also play a direct role in protecting soil in our homes.

How can you save carbon at home?

It is fairly simple to put your back garden to work for the climate. Key to improving soil health and carbon levels is to increase soil organic matter: the source of organic matter is plants.

“Making good quality compost with a wide variety of materials will help return nutrients and carbon to the soil,” says the Organic Centre’s Wheal.

“Watch the carbon nitrogen ratio! Not just too much green or grass clippings. Compost that gets hot collapses in on itself, you don’t get oxygen circulating and compost begins to ferment. Make sure to mix with shredded newspaper to build structure.”

Wheal advices that planting more trees such as nitrogen fixing alder and sea-buckthorn or shrub silverberry improves soil health and locks carbon in plant form rather than releasing atmospheric carbon.

All greenery acts as a cover to protect the soil, while roots improve soil structure which in turn boosts the soil’s ability to store water and carbon.

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Kate O'Brien

Kate is a freelance writer with work published in The Guardian, the Financial Times and the New York Times blog. She is a former Editor of The Plant, a UK magazine on plants and other greenery