Fine-scale drivers of sugar maple ( Acer saccharum ) habitat suitability at its northern range limit

At its northern range limit, climate change is increasing the uncertainty about the persistence of sugar maple (Acer saccharum). To inform climate adaptation strategies, we developed a high-resolution species distribution model using a Random Forest algorithm to identify currently suitable habitats, determine their primary environmental drivers, and project future shifts. The model, based on 3664 ground plots and built with fine-scale (20 m) topographic, soil, and climate data, demonstrated high predictive accuracy (76.4%) when tested against a spatially independent dataset (AUC = 0.868). Habitat suitability was found to be co-limited by topographically controlled moisture (topographic wetness index), soil fertility (cation exchange capacity), winter temperature stress (mean coldest month temperature), and wind exposition. Under a near-future climate scenario (SSP3–7.0, 2021–2040), we project a net increase in suitable habitat, with gains (~16%) significantly outweighing losses (~3%). Crucially, these gains are not uniform but form a complex spatial mosaic, highlighting where boreal-dominated landscapes are predicted to become suitable for this key temperate species. This provides a foundational roadmap for land managers to proactively establish climate-resilient forests, offering a significant opportunity to guide actions like assisted migration to the most promising sites.