Development and preliminary application of a Nature Value index to identify High Nature Value forests in the Republic of Ireland

•High Nature Value (HNV) forest are characterised by high levels of naturalness.•A framework for identifying HNV forest is proposed; six indicators were selected for constructing a Nature Value (NV) index.•The NV index was determined for 1676 NFI plots in the ROI and c. 11% of the forest plots were identified as HNV forest.•The framework presented can serve as a guide for HNV forest identification in other biogeographical regions.