Animals aren’t the only lifeforms aiding climate researchers. Consider the mangrove. These tropical plants live along coastlines and thrive in environments with salty and brackish water. If you find a mangrove tree, it’s a pretty good bet that you are about to find an ocean shoreline.

Or, in at least one oddball case, a past shoreline. 

Along the San Pedro Martir River, there is a red mangrove forest deep in the heart of Mexico. Far from any ocean, this particular forest has been a bit of a mystery until now. A collaboration of researchers from the University of California system and a variety of Mexican universities have studied the genetics of the trees, as well as other geologic and plant data, to piece together a story of a shoreline that did place these trees along a historic coast. 

About 125,000 years ago, the oceans were significantly higher and these trees naturally spread along that now shrunken ocean’s coasts. At the time, the Tabasco lowlands of Mexico were covered in water by an ocean that was nine meters higher than today. As the coastline receded, these trees were able to survive thanks to the unique combination of minerals in the river. 

This work is published in the Proceedings of the National Academy of Sciences and was led by Octavio Aburto-Oropeza. Coauthor Felipe Zapata explains: This discovery is extraordinary. Not only are the red mangroves here with their origins printed in their DNA, but the whole coastal lagoon ecosystem of the last interglacial has found refuge here.

While sci-fi stories of lost tribes of ancient humans have proved to be just stories, it’s kind of amazing to know that, for plants, that kind of a story was real.

More Information

UCSD press release

“Relict inland mangrove ecosystem reveals Last Interglacial sea levels,” Octavio Aburto-Oropeza et al., 2021 October 12, PNAS