If you want a perfect example of a fiendishly difficult problem, consider the dead zones in the Gulf of Mexico.

The dead zones are caused when nutrients from agriculture fertilizer or sewer systems get into the Mississippi River and then the Gulf. These nutrients help feed the algae blooms using up oxygen as they fall to the water bottom and decompose. Without significant mixing from waves or other turbulence, this lower layer of water can see such low oxygen levels that it no longer supports life.

It’s a long-standing concern, but so far, it’s been a complex issue to address.

A new set of researchers discussed their ideas in a new report in the Journal of the American Water Resources Association: Careful management of fertilizers on cropland in the Mississippi River drainage basin can help reduce the amount of harmful nutrients that flow downriver.

That’s not exactly a new conclusion, and there have been abortive efforts by states and federal agencies, pushed by environmental groups, to do just that. However, it involves millions of acres of cropland and a sheaf of different agencies of government, not to mention other interests in the enormous Mississippi basin.

As the researchers reported, only about a third of the reduction can be reached through these fertilizer management activities. The other two-thirds would require the construction of wetlands as well as having farmers plant cover crops — vegetation that helps keep soil in place. Both measures would help remove dead zone-causing nutrients before they get to the river.

“Just doing fertilizer management will not be enough,” said Eileen McLellan, senior scientist with the Environmental Defense Fund and lead author of the article.

That ought to be a dismaying result because of the difficulty of coordinating response to the issue of farm fertilizer alone. The other ideas, which could be added to a stronger farm program, are also very costly.

The U.S. Environmental Protection Agency has suggested that a 45 percent reduction in nutrients in the river is needed to get to an average annual dead zone size of 1,930 square miles, a goal set by the Mississippi River Gulf of Mexico Watershed Nutrient Task Force.

Last year, this dead zone of low oxygen was measured at 5,052 square miles across the coast of Louisiana.

A significant economic — and thus, political — challenge is in wetlands creation. The funding of restoration of land at the mouth of the river is already a huge challenge. Doing the same thing, albeit on a smaller scale, up the river adds new costs and difficulties.

The new report says that less than 1 percent of cropland in the Upper Mississippi-Ohio River Basin would be needed for the conversion to wetland to have an effect. Still, progress would remain dependent on steady but significant expenditures over a period of time, and coordination of federal, state and local entities. It is no small challenge.