In what Mexican and U.S. officials are calling an environmental catastrophe, up to 40,000 migratory birds have died since November after drinking contaminated water at an irrigation reservoir.
Hundreds more are dying every day, raising concerns that nearby residents may be exposed to the same toxic hazard.
As environmental groups fill mass graves on the banks of the government-owned Silva Reservoir, farmers and industry leaders bicker about what poison caused the disaster. Scientists blame the contamination on wastewater flowing from the vast tannery industry in nearby Leon, a city of more than 867,000 people.
“These are migratory birds and they’re coming from Canada and the United States. They fly long distances to find their tomb in the Silva Reservoir,” said Homero Aridjis, leader of El Grupo de los Cien, Mexico’s most prominent environmental organization.
The dead birds include American coots, American avocets, blacknecked stilts, mallards, ruddy ducks, northern shovelers, and both blue- and green-winged teals, biologists say. None is classified as an endangered species.
Local doctors are reporting cases of skin rashes, headaches and intestinal problems among children who have played in the water or handled dead or sick birds.
Industrial wastewater continues to flow into the 7-square-mile reservoir, and despite the overpowering stench it is still being used to irrigate wheat, corn and bean crops.