Loss of suitable climatic areas for Araucaria forests over time

Background: Araucaria forests are mountain ecosystems that might have expanded in the late Holocene, however past distributions remain uncertain. If current distribution reflects climatic conditions, past and future distributions may be projected using climate models. Aims: To contribute to the understanding of past and future distribution of Araucaria forests as a function of climate, we hypothesised that (1) they have increased their geographic distribution since the Last Glacial Maximum (LGM) until the present; and (2) would contract under predicted future climates. Methods: We modelled the spatial distributions of Araucaria forests under current, past and future climatic scenarios. Ecological niche models of 12 indicator species were developed using ensemble modelling. Results: The greatest extent of distribution of Araucaria forests appeared to have occurred during the LGM, after which a continuous retraction followed until the present. Our models suggested that Araucaria forests would experience an even greater retraction in the future. Conclusion: Araucaria forests could have covered larger areas during the LGM than suggested by earlier palynological studies, because climate was suitable for their distribution. The degree of loss of modelled distribution area since the LGM until today indicate these forests are likely to continue to shrink under projected future climatic changes.