Late Miocene greening of the Peruvian Desert

The question of whether tropical deserts expand or contract with global warming remains highly uncertain but has profound implications for the habitability of extensive low-latitude regions. We present the first paleobotanical study documenting the Peruvian Desert's response to the Late Miocene greenhouse climate, when radiative forcing was comparable to 21st century projections. Fossil leaves, wood, and pollen from the Pisco Formation lagerstätte indicate a diverse dry forest biome where an absolute desert is observed today. Rainfall at 8-6 Ma is estimated to have been three times higher than today, possibly due to a warmer Eastern Tropical Pacific Ocean or to more frequent El Niño events. Our results suggest that the impacts of tropical climate dynamics on ecosystems of the Pacific South American coast may exceed those of increasing evaporation under greenhouse warming conditions.