Multi-method late-successional and old-growth (LSOG) forest mapping uncertainty for Maine's unorganized townships

This dataset quantifies the uncertainty in mapping late-successional and old-growth (LSOG) forest across the approximately 4.2 million hectares of Maine's unorganized townships, and tests whether LSOG is rapidly disappearing. Three to four independent, credible mapping methods are compared on a common 100 m grid: (M1) a reproduction of the Hagan et al. (2026) airborne-LiDAR canopy random forest, rebuilt from their public Zenodo deposit; (M2) a logistic model of the FIA field-structure LSOG class on Potapov (GEDI-calibrated) canopy height; (M3) a direct canopy-height threshold; and (M4) the FIA structural class imputed to every pixel via USFS TreeMap (2016, 2020, 2022). Materials behind the formal Ecosphere Comment on Hagan et al. (2026): a cross-validated accuracy assessment (AUC) of each mapping approach on the original authors' own training plots; an FIA design-based estimate of older forest with sampling-error confidence intervals (older forest about 3.9 percent [3.3 to 4.6] and rising, including on private commercial timberland); a threshold-sensitivity sweep and a 20-seed reproduction ensemble; an ownership-resolved breakdown; a hex-scale (8 km) summary of cross-method disagreement; and the Comment manuscript and Supporting Information. Version 1.2.2 (this version): adds an explicit treatment of remote-sensing noise and GEDI geolocation error (Shannon et al. 2024), clarifying that no remote-sensing product is used as a reference and the design-based FIA estimate is the sole anchor. Version 1.2.1: a line-by-line fairness audit of the Comment against the original article (Deep_review_Hagan_vs_Comment) and the resulting language revisions. The Comment now credits the original authors' Limitations section, future-work proposals (canopy-gap and downed-log metrics), explicit ingrowth caveat, and citation of the national FIA and GEDI LSOG literature, and frames its contribution as quantifying caveats the authors raised qualitatively rather than disputing them. A citation error was corrected and the reproduced vs reported any-LSOG area (21.9 vs 19.7 percent) reconciled. Headline findings. Credible methods disagree by roughly 2.8 times on how much LSOG exists and on the location of most LSOG hectares, while agreeing closely on the rare, well-defined old-growth core. Top-priority protected sets selected by different maps overlap on only 16 to 30 percent of the ground. The design-based FIA estimate and TreeMap imputation both show older forest stable to increasing rather than rapidly declining; the apparent loss reported elsewhere is a gross harvest flux, not a net stock decline. Contents. Derived 100 m GeoTIFFs, summary tables, analysis R scripts, quick-look figures, the Ecosphere Comment manuscript and Supporting Information, the fairness-audit memo, and a full methods-and-findings report (PDF). No FIA plot coordinates are included.