On a hot, sunny day in California, I crawled into the tiny cockpit of a small Cessna aircraft to fly around one of the state’s most active volcanoes, Mt. Lassen.

Video by Peter Berger

I wasn’t looking for lava. The volcano in Lassen Volcanic National Park hasn’t erupted in more than 100 years. Instead, I was looking for the telltale signs of herbicide spraying across vast stretches of forestland. I’d already seen it from the ground: seemingly endless expanses of land devoid of plant life because glyphosate—a.k.a. Roudup—or similar herbicides were deployed to kill everything except young tree saplings being grown for timber. But it was hard to fully get a sense of the scale.

What would it look like from the sky?

I knew record amounts of glyphosate were being sprayed in California’s forests, much of it in the wake of the megafires that have hit the state in recent years. For our Mother Jones investigation, my colleague Melissa Lewis and I analyzed more than 5 million state records and found that the state’s fastest growing market for the controversial chemical was to spray forestlands.

That’s when the scale of the destruction hit me.

As the cramped little plane took off from an airfield in Chico, with me sitting in........

© Mother Jones