Dr Florence Renou-Wilson, Principal Investigator & Director of the MSc Programme in Global Change: Ecosystem Science and Policy at the School of Biology & Environmental Science, University College Dublin, explains the work of the AUGER project which surveys Irish bogs to assess the role of human activities on the climate footprint of our peatlands.
Peatlands have played an important role in climate regulation over the past 10,000 years. Natural peatlands are a small carbon sink (absorbing CO2 while emitting CH4) but 80% of Irish peatlands have been damaged to various extent. Anthropogenic disturbances, mainly in the form of drainage (for agriculture and forestry) and peat extraction, result in increased CO2 and nitrous oxide (N2O) emissions, and reduced CH4 emissions.
To mitigate emissions from peatlands, two actions are required: avoid new or recurrent drainage, and the reduction of emissions from existing drained areas. To provide for better climate policy instruments involving peat soils, basic information on the peatland resource and associated properties are required.
The key objectives of the AUGER project are:
Characterisation of peatland types (LUC - land use categories) and their associated edaphic and ecosystem properties. This will build on existing data to identify potential gaps to be filled and will be further informed by a nationwide peatland survey of physical, chemical and ecological properties of peatlands and peat soils (and overall assessment condition). Compilation of a database that regroups all types of peatlands under existing LUC.
Support of ongoing field observations and modelling of GHG emissions/removals at two core peatland sites: Moyarwood and Clara bogs to improve Tier 2.
Modelling of anthropogenic impacts on GHG emissions: development of the ECOSSE model to allow Ireland to move to Tier 3 level of reporting.
The research
A nationwide peatland survey was conducted across 50 ombrotrophic peatlands (bogs) in the Republic of Ireland to ascertain a wide range of peat properties, how they are affected by various management options and how this influences the carbon and GHG dynamics of these systems, thereby quantifying the role of human activities on the climate footprint of Irish peatlands. In addition to natural (relatively intact) sites, researchers surveyed the most prevalent peatland land use categories: grassland, forestry, peat extraction (both industrial and domestic), as well as management options (deep drained; shallow drained; rewetting) (Figure 1). The entirety of the peat profile (down to the sub-peat mineral soil/bedrock) was sampled and vegetation recorded (Figure 2).
Figure 1: Main land use categories of peatlands found in Ireland and surveyed in AUGER.
Figure 2: Rewetted raised bog with Russian Auger tool used to sample peat profile together with vegetation.
Our results demonstrate that Irish bogs have been drastically altered by human activities and the sampled peat properties reflect the nature and magnitude of the land use and management. Natural bogs were found to be the deepest of all LUC. When the residual peat depths under the other LUC are compared, a picture emerges of more intensive utilisation of raised and mountain bogs compared to lowland blanket bogs.
The shallower depths under all LUC (compared to natural sites) indicate high rates of subsidence and loss of peat through organic matter decomposition, as well as peat removal due to domestic and industrial extraction. Lowland blanket bogs exhibit the least degradation due to their more extensive utilisation.
Deep-drained grassland was at the extreme end of the degradation scale encountered (in comparison to natural bogs), containing the lowest organic matter and total organic carbon contents. However, combined with greater bulk density values, this LUC comprises large soil organic carbon densities and contains a valuable carbon stock. Nonetheless, high von Post (humification) and high ash content values indicate that this peatland LUC is very sensitive to continued organic matter decomposition and, thus, this LUC remains a potential hotspot of carbon dioxide (CO2) and nitrous oxide (N2O) emissions.
Despite a shallower peat depth, cutover bogs hold the largest soil organic carbon stock after natural peatlands regardless of peatland type.
These results infer the importance of these degraded ecosystems in providing some critical ecosystem services. Therefore, they should be identified for immediate management interventions to prevent further degradation, particularly the ongoing loss of their carbon store via gaseous and aquatic emission (Figure 3). For instance, our research demonstrated that a rewetted peatland resulted in a sustained and elevated water level and rapidly switched into a net sink of carbon after five years even though methane emissions remained elevated.
Figure 3: Schematics of gaseous (CO2: carbon dioxide; CH4: methane) and aquatic (DOC: dissolved organic carbon; POC: particulate organic carbon; DIC: dissolved inorganic carbon) fluxes in natural, drained, and extracted Irish peatlands.
Finally, work carried out on the ECOSSE model using an improved water table simulation approach (i.e., application of a seasonally varying drainage factor) could improve the model performance for the simulation of CO2 fluxes, thus contributing towards potential future development of process-based modelling approaches (IPCC Tier 3 methodology) for estimating and reporting greenhouse gas emissions from peatlands under various LUC/management practices.
Overall, recognition of the heterogeneity found across Irish peat soils, together with an understanding of the relationships between key soil properties, are critical to develop effective strategies for remedial management of these degraded ecosystems. This study and findings clearly support the need for a site-by-site approach for future rewetting management schemes.
All the results can be found in the EPA final and synthesis reports soon to be published.
Renou-Wilson, F., K. A. Byrne, R. Flynn, A. Premrov, E. Riondato, M. Saunders, K. Walz, and D. Wilson. In press. Peatland properties influencing greenhouse gas emissions and removal (AUGER Project). EPA Research Report., Environmental Protection Agency, Johnstown Castle, Ireland.
Dr Florence Renou-Wilson will present on the project for Peatlands Gathering 2021, October 7-9th - book your free online place.
For more information on the Auger project, email: Florence.Renou@ucd.ie
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