Oil absorbent material alongside the Yellowstone River in Laurel, Mont., July 6. (Jim Urquhart/AP)

The water near their farms is now coated with puddles of crude oil, and thick patches of the oil are discoloring the fields along the river.

Farmer Mike Scott told CNN, “I don't know what oil will do to the microorganisms that actually grow stuff. I am also worried that the remediation efforts will take forever, take 50-to-60 percent of this place out of production for an indefinite future.”

The oil spill came at a particularly bad time for Montanans, according to the Natural Resources Defense Council. The river is now at high flood, which causes the oil to be carried into neighboring fields and yards. The high flood causes the oil to be pushed downstream, which may cause it to affect bird habitats, and to be pushed into branch streams, which may cause it to affect harbor fish spawning grounds.

It was a bad week for Yellowstone National Park, with the oil spill occurring happening several days before a man was killed by a mother grizzly after he and his wife apparently surprised the bear and her cubs.