New reintroduction method makes conservation of fungi applicable at scale

Wood-inhabiting fungi are an increasingly threatened component of global biodiversity, yet conservation efforts remain limited in part by non-standardized, unscalable reintroduction techniques. We present the largest fungal reintroduction program conducted to date, using a standardized and scalable method adapted from commercial mushroom cultivation. Bulk spawn of seven red-listed species (Antrodia crassa, Antrodia infirma, Amylocystis lapponica, Skeletocutis stellae, Perenniporia tenuis, Radulodon erikssonii and Haploporus odorus) was produced and used to inoculate more than 1700 one-metre logs. Logs represented both natural host tree species and a locally available alternative, Betula pubescens or Betula pendula. In total, 53 forest plots in Finland and Sweden received inoculated logs. A subset of 465 logs was sampled to evaluate how wood type, inoculation method (sawdust versus dowel) and delivery time influenced establishment success. We found that strain identity is a major determinant of reintroduction outcome, with substantial variation among individuals within species. Inoculation methods performed similarly for most species, indicating flexibility in practical implementation. For several species, brief pre-translocation colonization in controlled conditions improved early establishment in the field. This study provides the first evidence-based, field-tested methodology capable of supporting fungal reintroductions at operational scales. By demonstrating high establishment success across multiple threatened species and forest contexts, it offers a practical conservation tool that enables the integration of fungi into mainstream ecosystem restoration and management.