Crisscrossing Mexico’s Yucatán Peninsula, a vast system of limestone caves forms a unique underwater world linking the region’s forests and towns to offshore coral reefs and the Caribbean Sea beyond.
In the second of our miniseries exploring these incredible aquatic wonders, we learn more from Dr. Patricia A. Beddows of Northwestern University, who studies the hydrogeology and geochemistry of these cave systems – and how manmade pollution moves through them to the ocean.
Q & A
So what makes the cenotes in Mexico so special?
When you visit the Yucatán Peninsula, you'll start to hear about these wonderful natural features called cenotes. They’re sinkholes, but unlike the sinkholes in Kentucky or even in Florida, because there's not very much soil, there are these beautiful windows where the cave underneath has collapsed and the rock has fallen down. Throughout the region, but especially in the area between Cancun and Tulum, you find some of the biggest known underwater cave systems in the world. There are probably chambers in these caves that are bigger than any room you've ever been in – and that includes Grand Central Station.
And they’re linked to each other?
They are well-connected – they very much function as underground rivers. You can be way back in the jungle, and if anything happens there, a development or something, and it impacts the water that's underground, that water is flowing. When we take measurements, what we're typically seeing is that the fresh water is flowing from the forest area underneath the cities and out to the coral reefs, and we're typically getting results of around 1.2 miles per day. So that means that it's flowing really fast.
Are they different from surface rivers?
Yes – because it's an underground river, there’s this idea that it would be really nice if there was a lot of filtration happening. But it doesn't. Because once something gets in the river, anything that we do on the ground's surface, ends up traveling all the way the ocean – and this is true of a lot of karst systems. It’s the same in the Bahamas, the same in Florida. What you do in one place, because the water connects us all, we have to be very thoughtful and careful of maintaining it from right where it starts, all the way out.
Where does the water flow to?
In the Yucatán Peninsula, what's particularly precarious, is that these underground rivers actually come out at the coastline and they discharge all their water out onto the Mesoamerican Barrier Reef system in the Caribbean Sea. To me, as a scientist, that’s really powerful because the reef is really old and it has developed and evolved to be there – and it's very dependent on certain conditions. That includes nice clear water, and certain temperatures and not a lot of nutrients. So, consequently, what we do, even many miles inland, the types of developments have really within even one or two or three days, can have a direct tie out onto the reef system.
Do cenotes interact with other aquatic ecosystems, like mangroves?
There's a beautiful and powerful ecosystem development in a number of types of cenotes. One thing that I'm always surprised at is the number of inland cenotes where we find mangroves that are actually healthy, and sometimes extensive – and that are completely growing in fresh water. I really want to underline to you how unbelievably globally weird this is. To the point where I have gone out of my way and taken photographs and sent them off to mangrove specialists.
How far inland are we talking?
Oh, like 25 miles from the sea! So that’s on the surface, and then where we have some geological features where there's been some really big fractures and some rifts happening, those have created more extensive, lowland and constantly wet areas. Those end up with some very extensive sawgrass.
So it’s clearly a vast area, but what is the general state of health of these ecosystems?
The region’s condition overall remains good, but where the development is happening, it is as profound and intense and fast as you could possibly make it. There will never ever be any, in my personal opinion, return to a functioning ecosystem state for any of those lands that have been developed and urbanized in the way that they're currently being urbanized.
Having said that, there’s a lot of the Yucatán Peninsula that remains in absolutely wonderful, gorgeous, pristine condition, and I want to highlight that there is a lot of traditional land use across the whole region. It's valuable to appreciate that people who live on the land and that it is their land, that we are not imposing an outside standard onto it. There's perhaps this idea that if something becomes a biosphere reserve that everyone who lives there in the present day has to be removed from the land and that's not how it works.
For more on Patricia’s work check out this video on cave science, which explores some of her geomicrobiology and geobiology projects in the cenotes.
In the next part of our miniseries, Parley Mexico coordinator Judith Adriana Morales López explores the hidden cenotes that lie beneath towns and cities — and how locals are working to protect them.
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