TRAVERSE CITY, Mich. (AP): A scientific report says reducing phosphorus runoff into Lake Erie enough to prevent harmful algae outbreaks will require big changes on the region’s farms.

The University of Michigan Water Center study says current efforts are falling short of what’s needed to achieve a 40 percent drop in runoff. The U.S. and Canada agreed on that target in February.

Excessive phosphorus is causing massive algae blooms, one of which forced a two-day tap water shutdown in Toledo, Ohio, in 2014.

The report says too few farmers are using voluntary best-management practices to stop runoff and stronger measures are needed, such as converting thousands of acres of cropland into grasslands.

The Ohio Farm Bureau Federation says that could put some farmers out of business.