The public land management agencies are phasing in a radically new approach to land management. They are shifting from their focus on individual resources to a more holistic approach of managing whole ecosystems. Fire-excluded systems are prone to changes in composition and density and are susceptible to catastrophic fire and invasion by non-native species. The cause of the problem in many areas includes more than a century of fire exclusion and suppression along with increased human development at the wildland-urban interface. Grazing and logging have also contributed to this problem.