The "perverted philosophy" of spontaneous development zones in which fallen tries are left on the ground is also at fault, President Milos Zeman said today about the fire that engulfed the Bohemian Switzerland national park, north Bohemia, a month ago. It mainly spread to thousands of dried-up trees attacked by the bark-beetle that were left in the forests, Zeman said at the start of the Zeme zivitelka agricultural trade fair.