A 30-year population decline of a threatened forest orchid associated with old growth forests

Intensive forestry practices have transformed boreal forest landscapes, with profound consequences for biodiversity. Species dependent on old-growth forest characteristics are particularly vulnerable to habitat loss and structural simplification. We analyzed population trends and habitat preferences of the red listed and legally protected orchid Goodyera repens using 30 years (1993–2022) of data from the Swedish National Forest Inventory, examining occurrence, colonization, and extinction probabilities in relation to stand characteristics. Goodyera repens declined dramatically over the study period, with occurrence probability decreasing from 1.9% in 1993–1997 to 0.6% in 2018–2022—a 66% decline. Occurrence probability increased strongly with basal area, stand age, and moss species richness, with basal area emerging as the strongest predictor across all models. The species exhibited a very low colonization rate (0.7% over 10 years) combined with high local extinction risk (75.2%), with extinction probability increasing sharply when basal area declined between surveys (e.g. due to clear-cutting). This reflects the fundamental mismatch between the species' requirements for old-growth forest conditions and modern forestry operating on 60–100 year rotations that prevent forests from developing old-growth characteristics. The 66% decline documented here is most likely a direct consequence of forestry practices that systematically remove old-growth habitat by harvesting forests at the stage when they become suitable for the species. Without fundamental changes to forest management that allow forests to develop and maintain old-growth conditions across the landscape, G. repens and other old-growth specialists will continue to decline toward potential regional extinctions in coming decades.