(Tierramérica) – The booming tourist industry along Mexico’s Caribbean coast, particularly in the area of Cancún and the “Riviera Maya,” is polluting the world’s largest underwater cave system and harming the world’s second largest coral reef, a new study has found.
Pharmaceuticals, cocaine residues, shampoo, toothpaste, pesticides, chemical run-off from roads and many other pollutants have been found in the immense system of underground rivers and aquifers south of the resort city of Cancún, located on the Caribbean coast of Quintana Roo state.
“There is little question the pollutants we detected have come from human activity along the coastal region,” said Chris Metcalfe, a researcher with the United Nations University’s Institute for Water, Environment and Health.
The British journal “Environmental Pollution” published a study by the Institute this month, titled ” Contaminants in the coastal karst aquifer system along the Caribbean coast of the Yucatan Peninsula.”
Metcalf told Tierramérica that pit latrines, septic tanks, leaking sewer lines and golf courses were the most likely sources of groundwater pollution.
The flow of groundwater takes much of this pollution into the coastal zone and the region’s famous Mesoamerican Barrier reef, the second largest in the world, after the Great Barrier Reef off Australia.
Land-based pollution is just one of the impacts on the coastal reefs, Metcalf said. Overfishing, coral diseases, and climate change have also contributed to an estimated loss of up to 50 percent of coral since 1990.
“Without serious attention to preventing groundwater contamination, tourist development will kill the goose that laid the golden egg,” Metcalf said.
That may already be happening. Divers have noticed the decline in the region’s reefs, says David Placencia, coordinator of reef monitoring for the Centro Ecológico Akumal (CEA), a non-governmental organisation in Akumal, 100 kilometres south of Cancún.
“They say they won’t be coming back,” Placencia told Tierramérica.
Studies by CEA found that a key reef-building species, Montastraea annularis, has suffered a dramatic decline. Twelve years ago it comprised 45 percent of the reefs around Akumal but in 2010 it had fallen to less than nine percent, he said.
Nutrients and contaminants from sewage promoted the growth of algae, which smother the corals, said Placencia.
There is no sewage treatment in the area, so the polluted runoff goes directly into the groundwater. “There definitely has been a big change in the reefs here,” he added.
The state of Quintana Roo is unique in that there are almost no streams or rivers on the surface because the region is comprised of very porous limestone. Instead, the world’s largest network of underground rivers, caves and sinkholes known as “cenotes”, and aquifers underlies the region. Much of this freshwater flows towards the coast and into the Caribbean Sea.
With a projected 10-fold increase in population through 2030, all of these problems are likely to worsen, according to the study by Metcalf and his colleagues.
When the Mexican government created the state of Quintana Roo in 1970, the region was entirely jungle and coastal mangroves, with a few small Mayan villages. Cancún was an uninhabited barrier island but is now a city with an estimated population of 700,000 and receives two to three million tourists each year. And the tourist development zone now extends 130 km south to Tulum.
Metcalf’s study sampled groundwater at five inland locations between Playa del Carmen and Tulum, well away from the biggest tourism developments.
“The levels of contaminants found are below those that are a human health hazard,” he said. One of the reasons for the low levels is the large volume and high flow rate of the groundwater.
However, most of the water flows toward the coastal zone and into the reef areas, and those low concentrations of contaminants accumulate there, he said.
By looking for caffeine residues, metabolites of nicotine and the ingredients of personal care products, the study proves that human sewage is getting into the region’s underground water supply.
One test site near a small golf course contained pesticides and herbicides consistent with those used in turf management, he said.
In addition, petroleum products were widely found and the source is likely the main highway that runs through the region, along with other roads and parking lots, he said.
“These findings clearly underline the need for monitoring systems to pinpoint where these aquifer pollutants are coming from,” he said.
“This is a solid study,” stated Brigitta van Tussenbroek, of the Autonomous National University of Mexico’s sea sciences institute.
Her own research has found high levels of nitrogen and phosphorus from wastewater in Puerto Morelos Reef Lagoon and the Nichupte Lagoon System in Cancún itself.
Van Tussenbroek told Tierramérica that she endorses the recommendations in Metcalf’s report about the need to build adequate wastewater treatment infrastructure and to end injections of treated sewage into saltwater below the freshwater aquifer.
Impermeable liners should be installed beneath golf courses and other grass-grown areas to restrict the leaching of contaminants, as well as in drainage canals, retention ponds and treatment systems to deal with the subsequent runoff.
“And such liners are especially needed under domestic waste dump sites,” Van Tussenbroek said.
Metcalf, meanwhile, stressed that it is difficult to comment on local government monitoring or environmental controls because there is little data available. Nor is it clear how well existing rules are enforced.
Tourism is king in Quintana Roo, and rules and regulations are ignored in favour of new development, said CEA’s Placencia.
Although it is illegal to harm coastal mangroves because they play a key role in keeping reefs healthy, their destruction continues nonetheless.
Without good ecosystem maps to identify where mangroves are located, developers bulldoze those ecosystems on their property and then claim their property never had mangroves, he said.
“And if they are charged with environmental violations, they just pay the fine and keep building,” Placencia said.
*This story was originally published by Latin American newspapers that are part of the Tierramérica network. Tierramérica is a specialised news service produced by IPS with the backing of the United Nations Development Programme, United Nations Environment Programme and the World Bank.