High rainfall helped the survival of equatorial rainforests at a time when Earth was globally warm and atmospheric carbon dioxide concentration was a whopping more than 1000 ppmv, around 50 million years ago.

The mechanism in which biota survives adverse conditions is still poorly known. The existing palaeoclimate data of mid- and high latitudes suggest large fluctuations in rainfall at around 50 million years ago. However, the quantification of terrestrial palaeoclimate data from the equatorial region was never attempted. Scientists are trying to explore the palaeoclimate data to probe the mysteries of survival under adverse conditions.

Scientists of Birbal Sahni Institute of Palaeosciences (BSIP), an autonomous institute of Department of Science and Technology, have quantified the terrestrial equatorial climate of around 50 million years ago using plant proxy. They reconstructed climate data and found that a significantly high rainfall was present during that time. The scientists have estimated that the high rainfall, most likely, increased the plant’s water use efficiency and afforded resilience to survive and remain functional under extremely warm and elevated carbon dioxide concentration at around 50 million years ago.  

It was earlier known that the Earth was around 13 °C warmer than present and carbon dioxide concentration was more than 1000 ppmv during this time. This drastically affected the survival of mid- and high-latitude forests due to changes in the hydrological cycle, but the equatorial forests survived successfully. The recent research published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology revealed for the first time, the mechanism of survival of equatorial forests when the Earth was much warmer than the present.

The study has also helped focusing on developing a calibration file from the low-latitude regions which will be useful in the quantification of seasonal deep-time terrestrial climate. Tracing the mystery of the survival of the rainforests – the biodiversity hotspots of the world is the Key to understanding climatic and biotic changes occurring at present and in the future.

Publication link: https://doi.org/10.1016/j.palaeo.2023.111762