Von Humboldt's Nightmare: Effects of Climate Change on the Plant Biodiversity of Mount Chimborazo (Tropical Andes)

ABSTRACT Aim Mountain plants are highly sensitive to the effects of climate change, and many species have shifted upwards and lost habitat as temperatures rise. Two centuries after Alexander von Humboldt and Aimé Bonpland's renowned expedition to Mount Chimborazo (Tropical Andes, Ecuador), significant upward shifts have been detected in the mountain's vegetation due to climate change. Here, we conduct a study to forecast the effects of climate change on the vegetation of Chimborazo in the future (2070) under intermediate (SSP2‐4.5) and pessimistic (SSP5‐8.5) climate change scenarios. Location Mount Chimborazo, Ecuador. Taxon Ferns and angiosperms. Methods We built Species Distribution Models (SDMs) for 134 native species of Chimborazo using MaxEnt, machine‐learning‐based downscaled bioclimatic and soil variables and GBIF occurrence points, and projected onto Chimborazo at a 30 m spatial resolution. Through high‐accuracy SDMs for 109 species (AUC mean = 0.978, TSS mean = 0.874), we analysed richness patterns, phylogenetic diversity and potential area changes into the future (2070) under SSP2‐4.5 and SSP5‐8.5 climate change scenarios. Results We predict upslope shifts in potential species richness to higher elevations in Mt. Chimborazo (≥ 4001 m), followed by only a slight increase in phylogenetic diversity with the rise of more closely related species ( p < 0.001). For lower elevations (≤ 2000 m), a decrease in species richness coupled with a pronounced increase in phylogenetic diversity may indicate changes in species assemblages in these areas ( p < 0.001). Most high‐elevation plant species may lose climatically suitable areas due to climate change, while the potential range of all low‐elevation species is predicted to increase. Main Conclusions The predicted future trends in our results are consistent with past observed upslope shifts in plant species distribution on the Ecuadorian Andes since von Humboldt and Bonpland's expeditions over two centuries ago. About 51% of the native species of Mt. Chimborazo, in our projections, may contract more than 1% of their potential ranges with climate change by 2070. This is particularly concerning to conservation as most of the studied species are not even present in the current IUCN Red List and also suffer from considerable knowledge shortfalls in taxonomy, observed distribution, and life‐history traits.