Since 2015, wildland firefighter and forester ­Patrick Haggerty of Wenatchee, Washington, has taken 900 local middle school students to explore the surrounding mountains, learning about wildfire risks. The Northwest is a fire-prone area, so Haggerty asks the students, “How many of you have ever been evacuated from home because of wildfires?” He always has several from each class raising their hands. During a hike, students view two kinds of forests. One is lush, with abundant trees towering over thriving shrubs and grasses. The other is patchy, with minimal ground vegetation and wide spaces between trees. “Which is healthier?” he asks. Thick greenery usually gets the nod. It’s often the reverse. Why? Consider the “fire triangle” of fuel, oxygen and heat. Remove any one of these, and the fire dies.