The Future Orchid Diversity of Great Britain and Ireland using an SDM Approach

Abstract: In this paper we use Species Distribution Models (SDMs) to forecast the future diversity and distribution of orchids in Great Britain and Ireland under scenarios of climate and land-use change. The study analyzes occurrence data for native orchid taxa in the BSBI database at a fine spatial resolution (1 km^2, monads) and incorporates multiple environmental variables including climate, land use, topography, and soil. These SDMs project significant losses in orchid species richness by 2050 and 2070, especially under severe climate and land-use scenarios, with declines expected across most species and regions, including Ireland where historical data previously indicated gains. The models reveal vulnerable species likely to face extinction by 2070, emphasizing the impact of both climate warming and habitat modifications. This approach differs from previous trend-based analyses by integrating future projections, high-resolution spatial data, and dynamic land-use scenarios, thereby providing higher-resolution estimates of orchid range contractions and diversity losses. While current observed orchid trends show some regional increases, particularly in Ireland, the SDM forecasts indicate substantial future risks. The study also discusses uncertainties due to niche truncation from geographic data limits and highlights the need for broader-scale modeling for more robust predictions. Overall, the paper anticipates conservation challenges for orchid biodiversity in response to ongoing environmental changes.