Ireland could benefit from greenhouse gas finding

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 more than 30 per cent of Ireland's total greenhouse gas 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 (such as carbon dioxide, the principal greenhouse gas) 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, and the atmospheric concentration of carbon dioxide has increased by 40 per cent over preindustrial levels. The Intergovernmental Panel on Climate Change has declared it “almost certain” that societal greenhouse gas 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 principal gases in the atmosphere are: nitrogen (78 per cent), oxygen (21 per cent), argon (0.9 per cent), carbon dioxide (0.03 per cent) and water vapour (0-4 per cent). Natural forces that add and remove these gases to and from the atmosphere help to keep them at these steady concentrations. Both water vapour 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 per cent) by agriculture to overall Irish greenhouse gas emissions reflects the relatively large size of our agricultural sector. In fact, output of greenhouse gases per unit of Irish agricultural production is low by international standards.

Planned growth in Irish food production would probably be severely curtailed by undifferentiated implementation of EU greenhouse gas emission targets (40 per cent reduction, relative to 1990 levels, by 2030; and 80-95 per cent 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 greenhouse gas emissions.

However, the EU promised at its summit in October to take the special position of agriculture into account when agreeing national greenhouse gas emission reduction targets. Also, a closer look at carbon dioxide emissions and "sinks" in grass-based agriculture would offer Ireland comfort in this dilemma.

Growing evidence

According to Prof Ger Kiely of UCC, 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 0.5-2 tons of carbon per hectare.

As grasslands cover nearly 60 per cent 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 Ireland is losing out on this issue and should lobby to be allowed to include Irish soil-grassland systems when accounting for carbon sequestration.

[ understandingscience.ucc.ie ]