About 1.6 million acres of grassland was removed from the Conservation Reserve Program (CRP) in 2013, which allowed the land to be planted to crops including corn, soybeans or wheat, reported “Environment & Energy News " pulling news from the NPR website.

The decline is in part due to Congress' cuts to the conservation program's budget, as well as the high price of grain that make it lucrative for farmers to plant more corn, soybeans and wheat. And ecologists have complained that the CRP-acre number does not account for other land that has been tilled and farmed on for the first time.

"I've seen things that I never thought I'd see here in South Dakota," said Carter Johnson, an ecologist at South Dakota State University. "With these land prices going up, there actually are people out there with Bobcats and front-end loaders, pulling out the rocks in hundreds of acres of land that's been in pasture all these years," reported Dan Charles per news on the NPR website.