Marine Life & Conservation
The Yucatan Cenotes – A paradise under threat from tourism
An interview with Sam Meacham by Jeff Goodman
A few years ago I made a film for the BBC called ‘Secrets of the Maya Underworld’ and was about the Cenotes and forests of the Yucatan Peninsula, Mexico. Previously I had always promised myself not to ever cave dive as I had a fear of being lost or trapped far underground with no escape route. Then a few very good friends told me of the Cenotes and the incredible wildlife that was associated with them. I had to see for myself.
It was then I met Sam Meacham, an American living near Cancun. He had been exploring the caves and passageways of the Yucatan Peninsula for the previous 18 years and now to date has discovered with other divers 252 known caves and cave systems in that region with a total of 1,103.3 km or 685.5 miles of surveyed passageway between them. Two of the five longest caves on the planet Sistema Sac Actun and Sistema Ox Bel Ha are found close to the town of Tulum.
The Yucatán Peninsula was once a shallow coral reef and now over a few million years has become a porous limestone shelf covered with forest and wildlife. There are no visible rivers; all the fresh water rivers are underground. Being porous, caverns and caves formed where the fresh water collects – hence the Cenotes or water sinkholes.
Recently, the Cenotes have become a great dive destination and the eastern Yucatan coastline an ever developing tourist area for sun worshipers and beach goers. The seemingly uncontrolled developments are taking their toll on this unique ecosystem.
I recently got back in touch with Sam to see if things were improving.
Jeff: Can you just tell us exactly what the Cenotes are and what is so special about them?
Sam: Cenotes are karst sinkholes that occur in Mexico’s Yucatan Peninsula. The Cenotes are windows into the freshwater aquifer of the region and the entrances to the very complex flooded solution cave systems along the Caribbean coastline.
Jeff: The underground water systems give life to the forests above where wildlife is obvious to find, but is there life in the caves as well?
Sam: Most people think of the cave environment as a very sterile place. In fact, there are over 40 life forms so far identified that live in the dark recesses of these caves. The majority are crustaceans and they are all considered extremeophiles because of the conditions they live in. The Cenotes themselves are also magnets for life; this includes a number of freshwater tropical fish species, crocodiles, turtles in the water and birds and mammals (including jaguars) at the surface.
Jeff: How long has man know about the Cenotes?
Sam: There is growing evidence that the caves and Cenotes were accessed by humans during the last ice age, which was 8000-10000 years ago.
Jeff: Did the Maya have any idea about the complexity of the underground waterways?
Sam: It is hard to say if the Maya realized that some of the Cenotes were connected by the intricate and complex cave systems. Many of the underground rivers flow out to the sea in very impressive upwellings; perhaps they put two and two together when they observed this. It was not until the 1980’s that cave divers really began to probe the depths of the Cenotes and really revealed just how complex and extensive they were.
Jeff: Are the Cenotes and reliant ecosystems in any threat now due to the commercial tourist developments?
Sam: There is a very real and continuing threat from the development of the tourism industry along the coastline. Karst landscapes like the Yucatan are very susceptible to contaminants that leach through the porous limestone and into the aquifer.
Jeff: What are the main issues?
Sam: The main issues we face are contamination from solid waste (garbage) and sewage. Once contaminants hit the aquifer there is the high potential for them to be transported through cave conduits and out to the Caribbean Sea. High concentrations of contaminants cause algal blooms that cover the Mesoamerican Reef and kills the corals. If we lose the reef, we lose the protection to the beaches. If the beaches erode, where will the tourists go? Effectively, we risk killing the goose that lays the golden egg.
Jeff: Is anyone listening to the conservation needs of the area or is commercialism taking its full toll?
Sam: Well, I think worldwide conservation efforts are always facing an uphill battle and this area is no exception. But I do think there is a great deal more awareness about the existence and importance of the flooded caves. My personal belief is that the outreach and education about the caves is the only way we can engage the public and effect change.
Jeff: As Divers, how can we help preserve this unique ecosystem?
Sam: If you dive in the Cenotes, it is a great opportunity to perfect your skills particularly your buoyancy and trim. Really, any time you go diving you should be perfecting your skills. We, as divers, are privileged visitors to the underwater environment and must make every effort to protect it.
Jeff: If readers want to learn more where can they get further information?
Sam: Here are a few websites:
Marine Life & Conservation
New report shows simple measures needed to cut beach plastic pollution
The Marine Conservation Society has launched its annual State of our Beaches 2023 report, highlighting the need for less single-use plastic items and more refillable options.
The charity’s beach cleaning programme, now in its 30th year, asks volunteers to record all litter that they find within a 100-metre stretch of beach. By gathering vital data from across the UK and Channel Islands, the charity creates change for cleaner seas and a healthier planet through policy and industry change. Last year, over 148 kilometres of beach were surveyed by volunteers, who removed 17,208kgs of litter from our coast.
Using data collected by over 14,000 volunteers, the State of our Beaches 2023 report shows that half of all litter collected came from public sources – either dumped, blown or washed onto our beaches.
Drinks-related litter, such as plastic bottles, caps and cans were one of the most found items, with an average of 16 found per 100 metres of beach surveyed. This figure is up 14% compared to the charity’s 2022 report.
Plastics caps and lids were recorded on 89% of surveys, with over 30,000 found in total. Plastic bottles were also commonly collected, with 73% of surveys finding this single-use item – a 4% increase compared to 2022. The charity’s inland litter pick survey, Source to Sea, also reported finding plastic bottles on 92% of cleans.
However, the charity’s State of Our Beaches 2023 report also indicates that some types of litter are on a downward trend. Although still in the top 10 litter items, disposable plastic cutlery, trays and straws were found on 5% fewer beaches across the UK, showing that bans on these plastic items between 2022 – 2023 could be working. The presence of plastic cotton bud sticks also dropped by 14%.
Lizzie Price, Beachwatch Manager at the Marine Conservation Society, said, “Half of the litter found on our beaches originates from public sources, underscoring the pressing issue of single-use plastic. Evidence shows that refillable alternatives and litter return schemes effectively reduce rubbish, as demonstrated by the decline our data has shown in items like plastic bags and disposable cutlery.
“Urgent and decisive action from UK governments is needed to accelerate our shift towards a circular economy, where we reuse, repair and recycle. The public needs greater access to refillable products and systems need to be implemented in which manufacturers are responsible for their waste.”
Governments across the UK have committed to delivering deposit return schemes from October 2025. However, the proposed scheme in England does not include glass items, despite glass being found on 52% of beaches in 2023. The charity is calling for governments across the UK to introduce compatible all inclusive deposit return schemes as soon as possible. This would see aluminium cans, and plastic and glass bottles have a 20p deposit which would be returned when recycled which would reduce drinks-related pollution.
Businesses are, however, starting to take refillable and reusable options into their own hands. Supermarket chain, Aldi, the largest corporate funder of the charity’s 2024 Beachwatch programme, is already leading the charge in refillable items by trialling refillable options for cereals and porridge oats in their stores over the past 5 months.
Plastics and Packaging Director, Luke Emery, from Aldi, who are running 4 beach cleans for staff and volunteers in 2024, said, “We are continually working to reduce single-use plastics and packaging, and making unpackaged product options more commonplace for our customers is a key part of this. We are really pleased with the uptake of our refillable range so far by customers. Not only are we making sustainable shopping more accessible, but we also offer refill products for a better price than the packaged alternative, helping our customers save money.”
Marine litter is one of the biggest threats to our seas, with plastic breaking down over time into microplastics and threatening marine life which can ingest or become entangled in them. The Marine Conservation Society is urging the UK Government to move faster on its policies to cut down plastic waste and prevent items from reaching our seas.
To find out more about the charity’s beach cleans and how to get involved, please visit mcsuk.org/beach-cleans
Blogs
Guarding Against Coral Invaders
Protecting (Dutch) Caribbean Reefs from Unomia stolonifera
Recent reports highlight the concerning spread of the invasive soft coral, Unomia stolonifera, currently devastating Venezuela’s marine ecosystems and detected in Cuba. With the potential threat of its expansion to the (Dutch) Caribbean islands, urgent action and awareness are essential to safeguard marine biodiversity and local economies from possible catastrophic consequences.
Invasive species are animals or plants from another region of the world that don’t belong in their new environment. These species can have major ecological effects by decimating native flora or fauna. They can also cause large economic losses and impact human health. Invasive species also pose a significant threat to marine ecosystems worldwide, including the Dutch Caribbean. Among these invaders is the octocoral species Unomia stolonifera or “Pulsing Xenia”, originally from the Indo-Pacific. With its rapid growth and lack of natural predators, this species can outcompete native species and disrupt fragile marine habitats such as seagrass beds and coral reefs.
Background
The invasive soft coral U. stolonifera was first identified in 2014, off the coast of Venezuela. It is believed to have been introduced via the illegal aquarium trade. Since this species can reproduce sexually and asexually (or fragment), even small pieces can regenerate to spread. Once introduced it quickly took over shallow reefs and hard substrate at depths of 0-50 meters, outcompeting local corals and seagrass for space. Follow on surveys found that this coral species exhibited average percentage cover as high as 80%, vastly outcompeting native corals. In highly colonized areas, fish are disappearing due to loss of habitats.
In 2022, during a survey conducted in Cuba by the University of Havana, an unknown octocoral was discovered which was later identified as the invasive Unomia stolonifera. It is suspected that the coral larvae arrived in ballast water from fossil fuel ships originating from Venezuela, as nearby sites adjacent to Venezuelan ports have been heavily affected by the invasion.
How to help
Prevention through continuous monitoring, particularly in high-risk areas such as marine harbors and oil facilities, is paramount. Early detection plays a pivotal role in mitigating the threat posed by Unomia stolonifera.
The public’s involvement and awareness are also vital. Local communities, recreational divers, tourists, and all stakeholders are urged to participate in early detection efforts by reporting sightings (photo, location and date) of this invasive coral to their respective Protected Area Management Organization (PMO’s)- the Fundacion Parke Nacional Aruba (FPNA), STINAPA Bonaire, CARMABI Curaçao , Saba Conservation Foundation (SCF), Nature Foundation St. Maarten (NFSXM) and St. Eustatius National Parks (STENAPA). If an invaded area is confirmed, follow the recommendations by the local PMO’s.
Keys to Success
Despite the challenges, early detection is key to mitigating the threat posed by Unomia stolonifera. With continued vigilance, research, and community engagement, there is hope for containing this potential issue before it becomes a major threat.
About the DCNA
The Dutch Caribbean Nature Alliance (DCNA) supports (science) communication and outreach in the Dutch Caribbean region by making nature related (scientific) information more widely available through amongst others the Dutch Caribbean Biodiversity Database, DCNA’s news platform BioNews and through the press. This article contains the results from several scientific studies but the studies themselves are not DCNA studies. No rights can be derived from the content. DCNA is not liable for the content and the in(direct) impacts resulting from publishing this article.
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