A post-fire reforestation assessment and prioritization tool for the Western United States.

Background: Increasing wildfire area burned has left millions of hectares in the western United States (US) in need of reforestation. Recent federal legislation allows for increased investments in tree planting to address the backlog of planting needs in previously burned areas. To support post-fire planning and assessment, we developed Regenmapper, a web-based decision support system (DSS) that provides spatial information on natural regeneration potential within post-fire environments. The program is freely available from a web browser (https://alpheus.dbs.umt.edu/regenmapper) and is designed to function across all land ownership categories for the 11 western States. Results: Regenmapper allows users to select historical wildfires or upload their own burn severity maps for recent fires. Within the burned area, it then predicts the potential for natural regeneration based on distance to mature live trees (seed sources) and hydroclimatic conditions. To this end, we developed 30-m resolution soil water balance and surface temperature models with corresponding projections for the 2050 period based on scenarios from the 6th Coupled Model Intercomparison Project (CMIP6). These data are used to estimate the probability of natural seedling regeneration based on historical or future biophysical conditions, respectively, and species-specific climatic tolerances. We also implement a simple planting prioritization algorithm based on distance to roads and the relative effects of dispersal and climatic limitations to rapidly identify accessible sites that are unlikely to reforest naturally. For US Forest Service managers, we develop an additional prioritization matrix based on fire severity, the probability of natural regeneration, and where federal law mandates reforestation when fires burn through recently harvested areas. Finally, we demonstrate model outputs in a case study approach through the 2017 Lolo Peak fire in Montana, US. Conclusions: Investments in tree planting will influence the extent and trajectory of future forests, but drought, climate change, and wildfires may challenge the ability of managers to re-establish forests over upcoming decades. DSS's like Regenmapper will benefit the planning and execution of tree planting efforts by reducing time required to conduct post-fire assessments and improving planting outcomes. Supplementary Information: The online version contains supplementary material available at 10.1186/s42408-025-00405-z.