Other industries, including wastewater treatment plants, contribute as well.
Moyle found that wild rice was sparse anywhere the sulfate concentration was 10 parts per million or higher. In 1973, in recognition of the grain’s cultural importance to the state, Minnesota adopted that as a standard specifically to protect waters that produce wild rice.
In a significant catch, however, with only one exception, the standard was never enforced, said Lotthammer — in part because no one was sure what a wild rice water actually was. “That’s what comes up every time,” she said.
Fast forward to the 21st century. The MPCA, partly because of questions raised by the Indian tribes and the U.S. Environmental Protection Agency (EPA), began to rethink its enforcement of the rule, and in 2010 decided to review it.
Industry groups, including the Minnesota Chamber of Commerce, were angered that the state was suddenly going to enforce the rule, and challenged Moyle’s science.
They said enforcing the standard could cost businesses and consumers millions of dollars and put the taconite industry at risk, as well as bringing a halt to the potential for a new copper mining industry. The chamber filed suit, but lost.
The Legislature tried to create a new standard, but the EPA overruled it, saying legislators couldn’t write a standard without the science to back it up.
Now, thanks to $1.5 million in state funding, the science is done. “We have, more or less, known that Moyle was correct,” Pastor said. “What we now know is why he was correct.”
Seedlings at risk
Sulfate by itself does not hurt wild rice. But when it gets down into the mud, microbes eat it and then it converts to hydrogen sulfide — that rotten egg smell familiar to anyone who’s found themselves tromping through a wetland. And sulfide is toxic.
“If conditions are right, it doesn’t take much … to have a serious mortality on seedlings,” said Pastor, who tested wild rice grown with different concentrations of sulfate in dozens of stock tanks.
Researchers also now understand what was always a puzzler — why wild rice sometimes appears to grow just fine in water that is high in sulfate.
It turns out that when water also contains dissolved iron, a chemical reaction renders the sulfide harmless.
The same processes affect all other aquatic plants except cattails, said Dan Engstrom, a research scientist with the St. Croix Watershed Research Station, who reviewed the results of tests conducted at 120 wild rice sites across the state.
“Wild rice may be the plant we worry about,” he said. “But it’s the whole ecosystem.”
Now, it’s up to regulators at the MPCA to figure out how to use that science.
“They’ve done a nice job,” said Tony Kwilas, director of environmental policy for the Minnesota Chamber of Commerce. ”It’s an important issue to our members, and we look forward to working with the agency.”
It is equally important to the Indian tribes and others who want to see those graceful stands of wild rice remain a common site across the landscape.