A Late Miocene paleobotanical record from the Peruvian Pisco Formation

Coastal xeric ecosystems face a major threat under the current global warming trend. Changes in water availability and precipitation patterns can contribute to the development of new landscapes and affect existing biotic interactions. The late Miocene, characterized by warm climates and comparable pCO2 values (∼400 ppm), presents an opportunity to understand future warming scenarios for dry coastal ecosystems. In this study, we present the first-known late Miocene paleobotanical record from the Peruvian coast (15ºS), where a non-vegetated desert is found today. Recalibrated leaf-based precipitation estimates indicate that coastal rainfall values were 4 times higher than today; while significant wetter conditions compared to the present existed on the western slopes during the austral summer. The combined paleobotanical record reveals a diverse community dominated by elements typical of modern dry forests rather than desert-like habitats, including a mixture of lowland and Andean wooded taxa. These findings suggest a substantial shift in the ecosystem that allowed the development of a greener woodland landscape along the central Peruvian coastal region during the warmth of the late Miocene. Although the sources of extra humidity remain uncertain, warmer sea surface temperatures in the eastern Pacific and local convection may have contributed to the additional moisture. Moreover, intensified or even a permanent El-Niño state during the warmer late Miocene could have potentially served as an additional moisture source. Regardless of the mechanism, our results provide compelling evidence of reduced aridity, leading to a greening of the coastal Peruvian desert and large-scale biome and landscape changes in response to the Miocene greenhouse climate.