By the end of this century, the striking climate and ecosystem changes currently seen in the polar Northern Hemisphere will likely span the globe. The biodiverse tropics, for example, are projected to warm by 1-4 degrees C. Tropical climate change is already evident, in the form of melting glaciers, declining precipitation, increasing temperatures, and a more frequent El Nino/Southern Oscillation. This project investigates tropical ecosystem sensitivity to climate change on Haleakala volcano in the Hawaiian Islands, USA. The study area brackets a changing climatic feature, the mean trade-wind inversion, where the cloud forest abruptly switches to shrubland. Tropical montane cloud forests, which are rich in endemic species and provide the vital ecosystem service of water capture and storage, are particularly vulnerable to climate change. To reveal how climate affects vegetation patterns today, this project compares detailed measurements of climate and vegetation in habitats ranging from mesic alpine grassland, through montane shrubland, and across the forestline into cloud forest. This study also uses microfossils preserved in lake sediment to look into the past and investigate how climate affected vegetation over the past ~10,000 years. Finally, this study analyzes tree cores to determine whether aridity controls the sharp upper cloud forest limit. This study combines analyses across broadly different time scales to predict tropical ecosystem sensitivity. Results from this study will guide managers from Haleakala National Park, Hanawi Natural Area Reserve, and The Nature Conservancy who are all actively engaged in controlling invasive species and conserving rare and endangered species across this unique landscape.
