Ms Lilian O'Sullivan:

I thank Dr. Moore for inviting me here and Senator Daly for his question on the science and where we are in terms of carbon stock sequestration and so forth. It is important to point out that Teagasc has been working in collaboration with partners since 2010 to explore the climate regulation potential of hedgerows and, in particular, their relevance to land-use budgets. Of course, we all know the linear structures we see in agricultural landscapes which consist of shrubs and trees. While they are primarily agricultural field borders and boundaries and form part of the farms, they are counted under the land use category in the inventories.

For the purpose of accounting mechanisms, there are a few things we need to know. We need to be able to give the amount of carbon stored in hedgerows nationally. We need to know the annual sequestration figures, that is the amount of additional new carbon that is stored in the growing hedgerow every year. To do that we need to know that the extent of the hedgerows, such as the width, height and the type, the extent of management that has been applied and, if there are trees etc., whether they are new or old. We need to know a typical amount of carbon that is stored in hedgerows, which is not only in the above-ground biomass. It is present in the woody biomass, in the leaves as well as carbon in the below-ground biomass in the roots and in the soils under the hedgerow, in addition to the leaf litter that is cycled back into the system.

In answering some of those questions, a lot of research has been done on understanding the hedgerow extent. The first hedgerow map was published in 2011, which estimated that 6% of the country was covered in hedgerow and scrub, non-forest trees and woody plants, with up to 12% cover in County Monaghan. Subsequent to that, there was a further project that used light detection and ranging, or LiDAR, a laser scanning technique. It was tested for its ability to estimate the amount of biomass from which the amount of carbon storage and sequestration can be inferred. From that work, we got some of the numbers that are often cited. We know LiDAR is very effective in accurately measuring biomass. Using published models, we are able to garner those national estimates. There is anywhere between 0.3 and 1.1 mega tonnes of CO2 per annum, which is not insignificant. As LiDAR is expensive, further projects were commenced. We have had the BRIAR project, which explored the potential of radar, but ultimately LiDAR or photogrammetry from aircraft or drone are required to get accurate estimates of biomass. We obtained the figure of about 680,000 km from that work.

One of the issues that repeatedly come up is that we need to take some direct measurements of biomass so that we can use them to quantify carbon stock changes for these inventories. The challenge is to track carbon stock change over time on a national scale. The current project I am leading is called the farm carbon project. In the earlier work, previously published models were used, but they were built on published forestry models. This is the first time we are characterising the relationship between biomass and carbon through field studies. Ultimately, what we are doing is relating biomass to a remote measurement that is then measured for carbon. We will then have true data that will allow us to build biomass functions whereby a remote measurement detects a certain amount of biomass that can then indicate a certain carbon stock. The idea is that one can see whether that increases or decreases over time. That work is ongoing. It is being pushed through the laboratory and we expect to publish results by September. We are also developing a scorecard that will allow for a rapid in-field assessment as to the quality of a hedgerow from a carbon perspective.