Before European settlement, healthy stands of widely spaced ponderosa pines and Douglas-firs covered the montane ecosystem. These open forests likely persisted because lightning-caused and human-set fires eliminated some young trees, pine needles, cones, limbs, and dead snags from the understory. After 1900, people began suppressing fires within the forests, increasing their density. Wildfires in thick forests are difficult and expensive to control, threaten people and property, lead to erosion and flooding, and can sterilize soils. Forests can be protected from dangerous fires through public education in wildfire prevention, forest thinning that opens spaces between trees to mimic the original forest structure, reduce the risk of hard-to-control crown fires, promote vegetation diversity, and provide wildlife habitat, and prescribed fires that decrease or eliminate flammable material in the forest understory without harming healthy, mature trees. These burns must be done regularly and carefully monitored. Burned plant material acts as a fertilizer and makes an area less susceptible to damage by future wildfires, insects, and diseases. In the long run, combining all three elements most effectively ensures the health of managed forests.