Ireland is underestimating the amount of land in arable production and is thus also underestimating its greenhouse gas emissions, according to new research.

Scientists at Trinity College Dublin suggests that recent practice in annual reporting on agricultural land use in Ireland is at odds with its cropland history.

They say, as a result, the research should have major implications for policy, with the new Paris Agreement fresh in our minds.

Ireland’s agriculture is dominated by grasslands, which are utilised by grazing animals for meat and milk production.

According to the Trinity team, this raises a number of environmental issues including phosphorus and nitrogen pollution, and large amounts of greenhouse gas emissions. Reporting on these issues requires precise knowledge of the area of grasslands and of other agricultural land use, mainly arable land.

Until now we have assumed that about 90% of the agricultural area is being used as pasture, with a relatively small area dedicated to arable land. We have also assumed that there are relatively small changes in land use over time.

However, recent research by the Trinity team, published in the journal Land Use Policy, shows that this view on Irish land-use needs to be re-evaluated.

Research Fellow in Botany at Trinity, and first author, Dr Jesko Zimmerman, said the team conducted an in-depth analysis, using the geographic database developed to assist farmers and authorities with the single-farm payment scheme, and found that agricultural land use in Ireland is much more dynamic than annual reports suggest.

While the area annually reported as cropland was on average 3,752 km2, this area has been shifting around the country.

In the 12 years for which data was available (2000 to 2012) only about half of that area could be considered permanent cropland (1,252 km2). In contrast, the area that showed arable history in the timeframe was 7,373 km2.

“Specifically, by looking at the 2008 to 2012 greenhouse gas commitment period set in the Kyoto protocol, we could show that relying on annual data and not including land-use history led to an underestimation of area reported as cropland by 45.7%, which in return impacts greenhouse gas accounting,” Dr Zimmerman said.