Satellite-derived evidence of recent peat surface elevation decline across the protected raised bogs of Ireland

Raised bogs are ombrotrophic peatland ecosystems whose long-term functioning depends on the stability of a vertically growing peat surface sustained by tightly coupled ecohydrological feedbacks. In intact systems, the peat surface undergoes reversible seasonal shrink–swell behaviour (“bog breathing”), allowing bogs to self-regulate in response to water-table fluctuations. Prolonged hydroclimatic stress or artificial drainage for land use activities can disrupt this oscillatory regime, leading to peat consolidation, loss of water-storage capacity, and progressive surface subsidence. Despite extensive national and EU-level protection, the stability of near-intact raised bogs has rarely been assessed at national scales.

Here, we use vertical ground-motion time series from the European Ground Motion Service (EGMS) data to quantify seasonal and interannual peat surface dynamics across raised bog Special Areas of Conservation (SACs) in Ireland between 2019 and 2023. Surface elevation changes were analysed for 52 paired raised bog sites representing both active raised bogs (habitat type 7110) and degraded raised bogs capable of natural regeneration (7120), using over 39,000 EGMS measurement points located within bog SAC boundaries. Long-term elevation trends were quantified using linear regression, alongside analysis of seasonal surface oscillations associated with bog breathing.

Across the study sites, almost all raised bogs exhibit clear seasonal surface oscillations alongside a persistent decline in mean surface elevation over the five-year observation period. Across the protected sites at the national scale, this corresponds to a median surface lowering of approximately 3 mm per year, with similar magnitudes observed in both active and degraded raised bogs. Mean subsidence rates are slightly more negative but remain within a narrow range, and variability across sites is moderate. These preliminary results indicate that long-term surface lowering represents a shift away from stable peat surface equilibrium in raised bogs designated for protection in Ireland, affecting not only degraded sites but also bogs classified as “active”.

Our findings indicate that water-level monitoring alone may not be sufficient to assess raised bog condition. Declining surface elevation reduces peat specific yield, meaning that apparently stable or high water levels can mask a loss of hydrological storage capacity and self-regulation. Consequently, raised bogs may appear hydrologically “healthy” while undergoing structural degradation and progressive subsidence. The surface elevation decline observed across almost all protected raised bogs highlights the need to integrate surface motion metrics into peatland monitoring, conservation assessment, and restoration planning to avoid irreversible ecohydrological degradation.