Irish Grasslands and Greenhouse Gas Emissions

Ireland’s greatest natural resource is probably its ability to grow grass. Agriculture is our main indigenous industry and the Government is committed to increasing food production up to 2030 and beyond. However, according to current accounting procedures, agriculture accounts for over 30% of Ireland’s total greenhouse gas (GHG) emissions, three times the EU average, and EU targets for reducing emissions pose a severe challenge to our food production plans. But, research at UCC and across Europe indicates that net carbon emissions (as carbon dioxide, the principal GHG) from soil-grassland ecosystems are much smaller than current official calculations. Ireland’s emission reduction targets would be greatly ameliorated if carbon accounting procedures took this research into account.

The world is warming (average of 0.8°C warming over the past century) and the atmospheric concentration of carbon dioxide has increased by 40% over preindustrial levels. The Intergovernmental Panel on Climate Change (IPCC) has declared it “almost certain” that societal GHG emissions accounts for much of this global warming and warns that, if these emissions continue unabated, global warming will accelerate causing disastrous flooding and climate change. The IPCC calls for severe reductions in societal GHG emissions in order to prevent such drastic consequences.

The principal gases in the atmosphere are: Nitrogen (78%), Oxygen (21%), Argon (0.9%), Carbon Dioxide (0.03%) and Water Vapor (0% – 4%). Natural forces that add and remove these gases to and from the atmosphere help to keep them at these steady concentrations. Both water vapor and carbon dioxide trap heat in the atmosphere.

Living organisms ‘burn’ sugars (respiration) to generate energy, releasing carbon dioxide in the process. Plants fuse carbon dioxide with water (photosynthesis) to make sugars, thereby removing carbon dioxide from the atmosphere and balancing respiration. However society also burns fossil fuels to generate energy for power, releasing extra carbon dioxide and raising atmospheric levels of this warming gas.

The large contribution (30%) by agriculture to overall Irish GHG emissions reflects the large relative size of our agricultural sector. Actually output of GHGs per unit of Irish agricultural production is low by international standards.

The farm sector accounts for 2% of Irish GDP, while the agri-food sector accounts for 8% to 9% of GDP. At present Ireland is grossly over-dependent on foreign multinational corporations – 75% of the annual value of Irish exports is multinational product. We need to further develop our indigenous industries, particularly agriculture and agri-food.

Planned growth in Irish food production would probably be severely curtailed by undifferentiated implementation of EU GHG emission targets – 40% reduction, relative to 1990 levels, by 2030 and 80% – 95% reduction by 2050. It is also unlikely that such reduced Irish emissions would even register in the atmosphere because the increased food production, needed to feed growing world populations, would move elsewhere where little priority is given to curtailing GHG emissions. However, the EU has promised (EU Summit 23/24 Oct. 2014) to take the special position of agriculture into account when agreeing national GHG emission reduction targets. Also, a closer look at carbon dioxide emissions and ‘sinks’ in grass-based agriculture would offer Ireland much further comfort in this dilemma.

Over the past decade, GHG measurements have been made in grasslands throughout the world, including Ireland. This research measures atmospheric carbon dioxide near the ground and determines whether net carbon dioxide is emitted from the soil-grassland ecosystem to the atmosphere or is taken from the atmosphere and sequestered into the soil-grassland system.

According to international expert Professor Ger Kiely of University College Cork, there is growing evidence that temperate grasslands in Ireland and Europe do sequester carbon dioxide. While grass (along with its carbon content) is either removed by harvesting for silage, or by grazing, additional carbon dioxide is now known to be sequestered (fixed) in the top 15cm of the soil. While some soils may be carbon-saturated, it is now considered that most are not, and have the potential to annually sequester about 0.5 to 2 tonnes of carbon per hectare. As grasslands cover nearly 60% of the Irish landscape, the quantity of carbon dioxide sequestered annually in Irish soils is enormous but is not allowed to be factored in under current accounting procedures. While Ireland does benefit in its carbon accounting procedures for carbon dioxide sequestered in forests, no such benefit is permitted to accrue for existing Irish grasslands. However, Ireland can use land changed over from say cropland (an emitter of carbon) to grasslands (which sequesters carbon) to benefit its carbon accounting obligations.

It seems that Ireland is losing out big-time on this issue and should lobby to be allowed to include all Irish soil-grassland systems when accounting for carbon sequestration.

(First appeared in The Irish Times on November 20th, 2014)

William Reville is an Emeritus Professor of Biochemistry at UCC. Understanding Science Website

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