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 1.2.6 (this version): the Comment was expanded to 14 pages with new supporting evidence: an out-of-bag confusion matrix and a probability-threshold sensitivity figure; a multi-measure temporal panel (FIA stand age, FIA large-tree basal area, and the TreeMap-imputed LSOG classification over time); a New England regional-context section showing older forest stable to increasing in all six states by design-based FIA; a current-protection analysis (only ~12% of Maine older forest is reserved, almost all public; the resource is overwhelmingly private and unprotected); and a demonstrated prototype multi-method ensemble LSOG probability with a companion per-pixel uncertainty layer (archived as 100 m rasters), shown as hex and bivariate maps. Earlier: document layout finalized (captions placed above tables and below figures, tables kept from breaking across pages, white space reduced) and a new section of concrete recommendations for future research added. Earlier: the manuscript was stress-tested, with every quantity re-verified against the source data, and a single orphan reference (the rapid field protocol, Shamgochian et al. 2025) was cited in the text; the verification is documented in the included audit memo (Deep_review_Hagan_vs_Comment). Earlier in the 1.2.x line: authorship corrected to the sole author; the framing broadened (all maps and models are wrong, the question is whether they are useful) and the tone softened; the Comment now credits the original authors' Limitations section, future-work proposals, ingrowth caveat, and citation of the national FIA and GEDI LSOG literature, and adds an explicit treatment of remote-sensing noise and GEDI geolocation error (Shannon et al. 2024), with the design-based FIA estimate as the sole reference. The conclusion names three practices: benchmark against a design-based inventory (FIA), cross-compare against an independent product rather than rely on a single remote-sensing map, and report accuracy and uncertainty on every quantity. The proprietary Seven Islands comparison was removed. A document build error that had frozen the manuscript PDF at an earlier draft in versions 1.2.0 through 1.2.2 is fixed here, so this is the first version to contain the complete, current Comment and Supporting Information. 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.