170 km from the sea, a mangrove grows in the interior of Mexico's Yucatan Peninsula. As these ecosystems usually only develop close to the sea, scientists and locals have long been curious about the origin of the mangrove. Now new research indicates that the biome carries valuable information about the sea level more than 100,000 years ago.

Mangroves depend on brackish water to exist. That is, they arise when the fresh water from a river mixes with the salt water from the sea, usually on the coasts of continents. For this reason, an interdisciplinary team of researchers found it very strange that a mangrove existed in the middle of the forest, so far from the ocean. The ecosystem is located around the San Pedro Martir River, betweenMexico and Guatemala.

Now, research published in the journal PNAS shows how the mangrove got so far out to sea, and what this has to do with the last Interglacial Period.

Image: Pat Josse / Pixabay

After genetic analyses, the team was first able to conclude that species such as the tree Rhizophora mangle have been in the region for at least the last 100,000 years. Estimates of sea levels over the last few thousand years have shown that at one point, between the last two glacial periods, the sea may have reached the forest region.

This happened, according to the research, between 125 and 130,000 years ago. That is, with the end of a glacial period, the giant polar ice caps melted significantly, raising sea levels. This may have been more than enough for the sea to reach the San Pedro Mártir River on several occasions.

However, when the planet cooled again, the sea retreated, leaving the mangrove stuck in the middle of the peninsula. This subsequently developed a more abundant rainforest.

What the mangrove says about global warming today

As the authors conclude in their article, understanding this process of dynamics of the sea and ecosystems can help us face the warming process that humanity has been creating in the planet's atmosphere.

The mangroves that exist today, for example, are extremely rich and diverse ecosystems that suffer drastically from warming and pollution. Therefore, this kind of information can help protect mangroves in the coming years - which are expected to be increasingly warmer.

Using botanical analyses, the team was also able to identify at least a dozen species such as the R. mangle This also shows the ability of organisms to adapt to new conditions and resources - within certain limits.

Image: Kon Zografos / Pixabay

"We hope our results will convince the Tabasco government and Mexico's environmental administration of the need to protect this ecosystem," the authors tell the UC San Diego News Center.

"The story of Pleistocene glacial cycles is written in the DNA of your plants, waiting for scientists to decipher it but, more importantly, the San Pedro mangroves are warning us of the dramatic impact climate change could have on the coastal plains of the Gulf of Mexico if we don't take urgent action to stop greenhouse gas emissions."