Beyond mapped area: Uncertainty-aware DEM screening of vertical deficits in Lithuanian cut-over peatlands

Cut-over peatlands are typically screened for restoration using mapped area alone, a metric that cannot distinguish a shallow disturbance from a deep vertical loss. We tested whether adding a digital elevation model (DEM) layer changes that screening order, for a national inventory of 162 Lithuanian cut-over peatland polygons (28,981.5 ha). Because no independent, field-surveyed reference elevations were available to validate any single DEM boundary surface, the analysis compares eight plausible reference-surface scenarios directly and reports where they agree or diverge, rather than selecting one as correct. The aim is to establish whether, and for which polygons, a vertical layer changes the priorities an area-only screen would set, not to produce a validated national peat-loss estimate. For each DEM-matched polygon, geometric deficit was calculated as the non-negative difference between mean interior elevation and eight local boundary-reference alternatives: 0.5 m and 2 m rings summarized by the mean, 90th, 95th and 99th percentiles. Computational coverage and a data-derived upper-outlier screen retained 122 polygons (16,911.5 ha); 40 polygons (12,070.0 ha) remained unresolved. Across the direct subset, the eight reference-surface alternatives produced volume-deficit totals of 26.0–444.7 million m 3 . Area and descriptive median-volume ranks were correlated (Spearman ρ = 0.877), but only five polygons overlapped in the two top-ten lists; the median absolute rank change was nine places and the maximum was 89. Thus, vertical information changed the screening order for some polygons, while the strong overall association confirmed continuing area dominance. For unresolved polygons, four area-only scenario models were compared by leave-one-out prediction of the DEM-derived scenario midpoint. The best internal model had a mean absolute error of 0.684 m; this is an internal prediction result, not a test of field accuracy. Combining eight direct-polygon alternatives with three unresolved-polygon alternatives yielded a deterministic national envelope of 193.2–741.8 million m 3 . An algebraic carbon conversion gave 35.4–136.0 Mt. CO₂ stock equivalent, not measured historical emissions or recoverable mitigation. The analysis shows how strongly the result depends on reference-surface choice and when a vertical DEM layer changes an area-based screen. Field-surveyed reference elevations and data on hydrology, biodiversity, feasibility and cost would be needed to move from screening to restoration priorities or a national peat-loss estimate.