Mapping Peatlands in Ireland using a Rule‐Based Methodology and Digital Data

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Abstract
Peatlands have been recognized as being an important global C pool and make significant contributions to national C fluxes. In Ireland, they cover a considerable amount of the national land area, but no recent inventory or mapping has been undertaken to quantify the spatial extent of this important resource. This study used a rule‐based methodology implemented as a series of hierarchical rules in ArcGIS to estimate the extent of contemporary peatlands in Ireland from soil and land‐cover maps dating from the 1970s, 1980s, and 1990s. The Derived Irish Peat Map was produced at a pixel resolution of 100 m and shows Ireland's peatland resource to be 0.95 Mha or 13.8% of the national land area. This is comparable to estimates of 13.2% from CORINE land‐cover data (1990s), 17.0% from the Peatland Map of Ireland (1970s), and 16.7% from the General Soil Map (1980s). The derived map depicts the spatial extent of three peatland types: raised bog and low‐ and high‐level blanket bog. Ground truthing of the derived map enabled estimates of pixel reliability to be calculated. The derived map has an overall reliability of 75% compared with the reliability of 65% for CORINE, 58% for the Peatland Map of Ireland, and 50% for the General Soil Map. We concluded that the methodology created a value‐added soil map product from a number of data sources, all of which were to some degree imperfect. The approach taken could be applied to similar survey problems not related to peatlands.
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