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Watch Ireland’s Grasslands and Carbon

In the sixth in this series of Climate Conversations held on 24 November 2021, Professor Matthew Saunders gave a talk on Ireland’s Grasslands and Carbon.

Ireland’s Grasslands and Carbon

Grassland ecosystems form an important part of the Irish landscape, covering over 60% of the total land area. Many of these grasslands are intensively used for agricultural production, which can alter carbon stocks and flows and result in the production and emission of important greenhouse gases such as methane and nitrous oxide. The influence that this type of land use has on climate is reflected in the national greenhouse gas emission inventory, where agricultural emissions constituted 28.8% of total emissions between 2010-2017. This talk will discuss our current understanding of the role that grasslands pay in the wider climate debate, and will focus on whether these systems act as a net sink or a source of carbon. The influence of soil type, climate and management intensity will also be discussed as well as highlighting how recent work has provided further insight into how we can improve estimates of greenhouse gas emissions from these systems. Finally, we will discuss potential site-specific mitigation options that can increase the sustainability of these systems by both enhancing carbon stocks and reducing greenhouse gas emissions.

The presentation is followed by a Q&A session chaired by Climate Change and Environmental Sciences Committee Member, Professor Pat Brereton

Q&A Session

Q1. Are solutions to reducing greenhouse gas emissions from grasslands available and how could they be implemented at the farm level?
There are many simple mitigation options that can be applied at the field scale, these include nutrient management, planting mixtures such as multi-species swards and stocking rates. There are also new approaches being trialled to address this globally such as changing animal feeds, although this can have knock-on effects to other systems, burying carbon at depth in the soil profile during re-seeding or considering agroforestry options to increase carbon assimilation and provide additional fodder. Each farm and field may differ however, so we need to understand the characteristics of each site to provide a more targeted approach for farmers.

Q2. How much variation is there in soil carbon stocks across the different grassland management regimes?
There are substantial differences, depending on soil characteristics but this is also influenced by many other differences in management regimes and how the intensity of management impacts the carbon stored within the soil.

Q3. What density of top down monitoring sites is required to understand the spatial variation in GHC emissions and how much do the monitoring sites cost?
It is important to develop long-term monitoring sites across the range of soil types and management intensities found across Ireland to better characterise the carbon and greenhouse gas emission profiles. The infrastructure required for these sites is expensive however, with equipment to measure all key greenhouse gases, ancillary variables and to provide consistent power costing up to €200,000 per site. The Department of Agriculture Food and the Marine has made significant investment in Teagasc to develop the monitoring network and over the next few years the Teagasc GHG centre of excellence and the National Agricultural Soil Carbon Observatory (NASCO) will return the information required.

Q4. What models are available to integrate all this detailed measurement of carbon content and GHG fluxes?
Some site-specific well established models such as DNDC, Daycent and ECOSSE are available and these are being developed for use at national level and to align with wider Earth systems models in ongoing projects such as the Teagasc GHG centre of excellence, the National Agricultural soil Carbon Observatory (NASCO) and the Science Foundation Ireland funded Terrain-AI project.

Q5. Are there other national research programmes that we can learn from and/or collaborate with?
New Zealand is a good example of a country with comparable grassland systems and climate that we currently collaborate with.

Q6. What research topics are the most important to follow at present?
Organic soils should be the focus as they are strong net emitters of GHGs and there is huge scope to reduce GHG emissions from them. There is also a need to improve our ability to measure the rate of change in carbon stocks in soils under different management regimes. There is a potential for the use of stable isotopes of carbon to monitor these changes and to better identify how protected carbon is once bound within the soil.

Q7. How does livestock density and their grazing activity influence GHG emission intensity?
Higher management intensities can lead to higher emissions but there are mitigation options to manipulate intensity of grazing to regulate GHG emissions, but this would need to be incentivised.

Q8. What are the implications of climate change for carbon stocks and GHG emissions?
Warming can lead to increased GHG emissions from soils, in particular carbon losses from drained organic soils, but this response will interact with changes in rainfall patterns and drying or wetting of soils. Variability in temperature and water availability will also likely influence the rates of carbon assimilation and potential sequestration by plants which may exacerbate climate impacts further.

About the Climate Conversations Series

This lunchtime webinar series organised by the RIA Climate Change and Environmental Sciences Committee in collaboration with the EPA provides policymakers and key stakeholders an opportunity to engage with recently published research on climate change in Ireland, addressing the causes and consequences of climate change as well as availing of the opportunities that arise from the social and economic transition and transformation that is required.