An adaptive mapping framework for the management of peat soils: a new Irish Peat Soils Map.

Abstract

Accurate mapping is necessary for effective management of peat soils to help reduce GHG emissions and improve environmental quality. However, mapping peat soils remains a major challenge: definitions of peat soils vary substantially, field data are sparse and difficult to produce, and remote sensing of limited use for converted peatlands. Using an Adaptive Mapping Framework developed for the Derived Irish Peat Map, this study describes our work to update the map with refined and new datasets. These include incorporation of areas considered to be underlain by shallow peat soils (≥ 10 cm and ≥ 8.6 % Organic Matter content), and augmentation of the overall test dataset with an additional ~ 20,000 points. The workflow for map generation employed 20 Decision Tree Output Maps (DTOMs), aggregated into 33 Map Combinations (MCs). The MC selected for the update had the highest accuracy metrics (≥ 80 %), consisting of DTOMs with a user accuracy ≥ 60 % and assessed over a minimum number of test points ≥ 50. The resulting map reveals peat to underlie 1.66 M ha of Ireland (~ 23.3 % of the country), with an overall accuracy of 84 % and a F1 score for peat areas of 85 %. This extent is 13.2 % larger than that delineated in previous versions and at least 18.8 % larger than areas presented in other previous maps. The methodology also allows transparency from which data sources the different peat layers of the new map are coming from and to distinguish different peat thickness ranges (≥ 10 cm, ≥ 30-40 cm). We demonstrate the utility of the mapping framework to facilitate the production of a more reliable peat map than previous mapping attempts. This approach has potential relevance for peat mapping elsewhere, in areas containing disparate datasets (e.g., land cover, soil map, etc.), covering different time periods, or employing different production methods. The accuracy metrics generated also suggest that the approach can be used as a basis for implementing or updating European and national regulations concerning carbon-rich soils in comparable settings to those encountered in Ireland.