‘Hedgerows sequester 50% more carbon than forestry’ – Dr. Paddy Wall

The potential for Ireland’s hedgerows and grasslands to be acknowledged as carbon sinks on farms proved to be a major talking point at last week’s Arrabawn Dairy Conference.

The conference – which was held at the Abbey Court Hotel in Nenagh, Co. Tipperary – included a diverse range of industry speakers.

During a presentation from University College Dublin (UCD) professor of public health Dr. Paddy Wall, he pointed out that “hedgerows sequester 50% more carbon than forestry”.

“We need policymakers to recognise that, so that farmers are actually acknowledged for carbon sequestration. It’s not just about reducing it [carbon emissions]”.

People are angry about farmers; but farmers are actually working hard to sequester more carbon.

The professor’s comments come amid much discussion on the topic of Ireland’s farming footprint in recent weeks.

Last month – in a series of interviews with AgriLand – Dr. Frank Mitloehner a global air pollution expert at the University of California in the city of Davis, in the US, also highlighted recent US Environmental Protection Agency (EPA) research which found that agriculture and forestry combined are a “greater sink than source of greenhouse gases [GHGs]”.

However, questions remain as to whether this can be explored further in an Irish context in the short term, as a roadmap to reduce Irish agricultural emissions up to 2030 is already in place.

Farmers were eager to discuss this area further at the Arrabawn event.

A farmer from the audience asked the following question to the panel of speakers – including: Conor Mulvihill director of Dairy Industry Ireland; Trevor Donnellan Teagasc economist; Jack Nolan senior inspector at the Nitrates, Biodiversity and Engineering Division at the Department of Agriculture, Food and the Marine; and Dr. Paddy Wall.

He asked: “We just heard tonight that a hedge will sequester 50% more carbon than a tree.

“When any farmer opens their door, the first thing they are going to see is either a tree or a hedgerow.

“Considering that Irish agriculture accounts for 34% of our total carbon emissions – are our existing trees and hedges being included in that calculation?”

Rigorous science

Teagasc’s Trevor Donnellan offered a detailed response:

“We don’t have any science done to prove the carbon sequestration that is taking place; and we don’t have the methodologies in place to count all that stuff up in a way that would be accepted.

“The way GHG emissions are calculated in countries is verified by other countries. People will come to Ireland and check the way we calculate our GHG emissions or our carbon sequestration – if a country is deemed to have ‘cooked the books’ basically you will be found out.

So you have to follow a very rigorous methodology when you are producing your figures.

“So hedgerows no, and grasslands no [they are not included in the 34%].

“But what I would say is some people are going around thinking that these are the ‘get out of jail’ card for agriculture. They are not.

“These things might help us; but they are not the ‘magic bullet’ or ‘get out of jail card’ for the sector,” he said.

However, another farmer from the audience contested Donnellan’s assertion saying:

“We have mechanisms in place for measuring gas coming out of cows; we have mechanisms in place for all sorts of things; and we have mechanisms in our mapping system that are able to tell us if our hedgerows are growing out too much.

“So I don’t buy that for a second that we don’t have the mechanisms in place,” he said.

Hedgerow credits?

Department inspector Jack Nolan also contributed to the discussion saying:

Dairy farms leak 9t/ha/year and the grass may sequester about 3t – so you are still a net emitter.

“No matter what, you are a net emitter because you have the extra cows and you have the extra nitrogen (N).

“One hectare of Sitka spruce will sequester the carbon produced by three cows.

“We have expanded by 400,000 cows over the last few years; so we need a lot more forestry, if forestry is the answer.

“But the people up in Co. Leitrim don’t want anymore forestry.

“You are right, we do have a very good mapping system; but we talked to an expert in the EPA about hedgerows, and he said that ‘on average’ there are about 600ha/year of habitats and hedgerows removed in Ireland.

The damage done by that is almost balancing out the good that is being done by the dairy EBI [Economic Breeding Index].

“So we are not in a place yet to get credit for hedgerows – and if we are to get credit, it is going beyond what we are doing, or what would happen naturally.

“If we left the hedgerows alone they sequester carbon; so what we are doing is extra and that is what we get credit for,” he stressed.

‘Not good enough to say we don’t have the science’

However, UCD’s Dr. Paddy Wall shared a different opinion adding:

“I think we need to tell the best story we can; so it is not good enough to say we don’t have the science; we need to get the science to do it right.

“Teagasc is doing a lot of work on this on balancing, so that farmers get the credit for the carbon sequestration.

“You need to get the credits for grass; you need to get the credit for hedgerows and we need to document that and tell that story,” he said.