The forest floor was nothing but patches of brown. No ferns, no brush, no flowers, and definitely no wildlife. Everything was dead except for rows of hand-planted baby trees.

This is what reporter Nate Halverson found while mushroom foraging in the California wilderness near Lassen Peak. He would learn the area had been sprayed with the controversial weed killer glyphosate, more commonly known by its brand name, Roundup.

This week on Reveal, Halverson’s yearlong investigation reveals that the US Forest Service and timber companies are spraying glyphosate in record amounts in California’s forests in an effort to regrow timberland that’s been decimated by years of megafires.

“The wedding of the chemical industry and the Forest Service has got to be seriously and deeply looked at,” Craig Thomas, a fire restoration expert, says about the spraying. The Forest Service is “addicted to herbicide use and glyphosate, and we need to get them into rehab.”

Read: We Are Bombarding America’s Forests With Roundup (Mother Jones)

Watch: The Secret Plan to Cover the World in Herbicide (Mother Jones)