A mangrove forest thrived on an island in the Panama Canal until a violent volcanic eruption 22 million years ago buried it under ash and rock and wiped it off the planet.
Now scientists at the Smithsonian Tropical Research Institute have found the fossilized remains of the trees that once stood on the shores of Barro Colorado Island.
A total of 121 preserved pieces of wood were found that still have their specific features such as water vessels.
In addition to rediscovering the long-lost forest, the team discovered that it is teeming with a species that no longer exists on Earth today.
Scientists at the Smithsonian Tropical Research Institute have found the fossilized remains of trees that once stood on the shores of Barro Colorado Island
Scientists cut and polished sections of the petrified wood and photographed them under a microscope. They focused on specific features such as water vessels (B, D, H and I) that can distinguish one species from another
The fossil evidence suggests that a single large volcanic eruption triggered a lahar, a violent flow of water, mud, ash and rocks.
A lahar flows like wet concrete at breakneck speeds and can cover an area instantly. It leaves no opportunity for plants and animals to rot or decompose.
Add to this the silicon-rich water of a lahar that penetrates living things and fossilizes their tissues, and the result is well-preserved fossils captured in a specific moment.
Scientists found the fossils in a stream on Barro Colorado Island.
In the early Miocene, about 23 million years ago, the major landmasses of South America and the Caribbean Plate collided, shaping the landscape of Panama and the rest of Central America.
Scientists found the fossils in a stream on Barro Colorado Island
Mangroves that grow in warm areas with high rainfall and few storms can reach extraordinary heights. Researchers estimate that the trees in the Barro Colorado Island mangrove forest were 130 feet or taller
At this point, the hill that would later become Barro Colorado Island rose from the sea.
A mangrove forest grew along its edges, with trees reaching up to 130 feet into the air, the study authors wrote.
Sediment samples show that the forest grew in the brackish water zone where salt and fresh water meet, ideal conditions for mangroves.
The absence of other tree fossils in the area suggests that other species would have had difficulty living in this habitat.
It wasn't just the brackish water that created ideal conditions for a huge mangrove forest.
Atmospheric carbon dioxide concentrations were much higher in the Miocene than today – over 500 parts per million (ppm), compared to about 419 ppm today.
In addition to rediscovering the long-lost forest, the team discovered that it is teeming with a species that no longer exists on Earth today
The island lies in the Panama Canal
Barro Colorado Island, home of the Smithsonian Tropical Research Institute, sits in the middle of man-made Gatun Lake. The island was once a hilltop, but the lake surrounded it when the Panama Canal was completed over 100 years ago
Because trees use CO2 to grow, the study authors concluded that these ancient species could have reached much greater heights than today's mangrove trees.
Scientists have named the tree Sonneratioxylon barrocoloradoensis – the first part is the genus it belongs to, a group that still exists today. The second part of its name indicates where it grew: Barro Colorado Island.
The species has some living relatives in the genus Sonneratioxylon, but only in Southeast Asia – there are no longer any in South or Central America.
These results will be published in the March 2024 issue of the journal Palaeogeography, Palaeoclimatology, Palaeoecology.
The remaining relatives of fossilized mangroves are found in Southeast Asia. None remain in Central or South America
However, the same geological activities that formed Barro Colorado Island also spelled the end of this ancient forest.
Sometime after the forest's formation, up to a million years later, a local volcano erupted.
Its ash and stones, along with existing water and mud, covered the trees in a lahar.
The authors concluded that fossil evidence, including the volcanic sandstone surrounding the tree fossils, suggested it was probably just one large eruption that covered the trees.
However, this forest was probably not alone.
The study authors wrote that these local extinctions likely occurred around the world since the Miocene.
After all, the same conditions that created and destroyed this forest existed across the changing Earth: the planet's shifting plates pushed land upward, then mangroves formed, and volcanic activity destroyed them.