Why Cenote Conservation Matters
Cenotes are not just swimming holes — they're windows into the largest underground freshwater system in the world. The Yucatán Peninsula has no rivers or lakes on its surface. All fresh water flows underground, through a vast network of limestone caves and channels that connects cenotes to each other and, ultimately, to the Caribbean Sea. This aquifer provides drinking water to over four million people across the peninsula.
When a cenote is contaminated, the contamination doesn't stay local. It travels through the underground system, affecting other cenotes, wells, and coastal ecosystems kilometres away. Protecting cenotes means protecting the Yucatán's entire water supply.
The Threats
Chemical Contamination
Sunscreen, insect repellent, shampoo, and other personal care products wash into cenote water and are nearly impossible to remove from a cave system. Oxybenzone — the active ingredient in most standard sunscreens — is toxic to freshwater microorganisms at concentrations as low as 62 parts per trillion. With hundreds of visitors per day at popular cenotes, the cumulative effect is significant.
This is why every cenote requires biodegradable sunscreen and a shower before entry. It's not a suggestion — it's the most impactful thing any visitor can do.
Overdevelopment
The Riviera Maya is one of the fastest-growing tourism corridors in the world. As hotels and resorts expand, construction breaks into the limestone substrate, disrupting cave systems and introducing concrete, chemicals, and sewage into the aquifer. Some cenotes that were pristine a decade ago now show elevated levels of nitrates and coliform bacteria.
Sewage and Agricultural Runoff
Much of the Yucatán's waste water is processed through septic systems that drain directly into the limestone — and from there into the aquifer. Large-scale pig farming in the Yucatán interior contributes significant nitrogen and phosphorus runoff. These nutrients promote algae growth in cenotes, reducing water clarity and displacing native species.
Solid Waste
Plastic bottles, food wrappers, and other refuse thrown into or near cenotes persist for decades in the cave environment. Underwater cave cleanups have recovered everything from tyres to refrigerators from cenote systems.
Cave Formation Damage
Stalactites and stalagmites in cenotes formed over thousands to millions of years in air, before the caves flooded at the end of the last ice age. A single touch deposits oils that permanently stain the mineral surface. A careless kick can break a formation that took 100,000 years to grow. This damage is irreversible.
What Scientists Are Doing
Researchers at institutions across Mexico — including UNAM, CINVESTAV, and the Gran Acuífero Maya project — are mapping the underground cave systems, monitoring water quality, and studying the unique species that live in cenote environments. The Yucatán's caves are home to endemic species found nowhere else on Earth, including blind cave fish, cave-adapted crustaceans, and unique microbial communities.
The Gran Acuífero Maya initiative has mapped over 1,500 km of underwater cave passages and advocates for aquifer protection at the government level. Their work has demonstrated that the underground systems are far more interconnected than previously understood — pollution at one point can travel surprising distances.
What Visitors Can Do
Before Your Visit
- Buy biodegradable sunscreen before you arrive. Apply it at least 20 minutes before reaching the cenote so it absorbs into your skin rather than washing off in the water.
- Skip the insect repellent on cenote days, or apply DEET-free alternatives at your accommodation and let them absorb fully.
- Choose community-managed cenotes when possible. Revenue from these cenotes goes directly to the Maya communities that steward them, creating an economic incentive for conservation.
At the Cenote
- Shower thoroughly before entering, even if nobody is watching.
- Don't touch rock formations. Not the walls, not the stalactites, nothing.
- Stay on marked paths. Trampling vegetation around cenote openings accelerates erosion.
- Take all waste with you. If there's no bin, it goes back in your bag.
- Don't feed the fish or turtles. Human food disrupts their diet and behaviour.
After Your Visit
- Leave reviews that mention conservation. When cenote operators see that visitors value environmental practices, they invest in them.
- Support conservation organisations. The Gran Acuífero Maya project and local ejidal (communal land) cooperatives accept donations that fund cave mapping, water monitoring, and community conservation programs.
- Talk about it. The biggest threat to cenotes is that most visitors don't understand what they are — they see a swimming pool, not a critical freshwater ecosystem. Sharing what you've learned makes a difference.
The Balance
Tourism isn't inherently bad for cenotes. Done responsibly, it provides the economic justification for communities to protect cenotes rather than allow them to be used as dumps or drained for agriculture. The cenotes around Homún, for example, are in far better condition today than they were 20 years ago, precisely because ecotourism has given communities a reason to invest in their protection.
The challenge is scale. A cenote that handles 50 visitors a day can maintain its ecosystem. A cenote that handles 500 cannot — not without serious infrastructure for water treatment, waste management, and access control. As cenote tourism grows, the need for regulation and visitor responsibility grows with it.
Browse all cenotes and choose ones that align with responsible travel.