Unlike the wetter regions west of the Cascades, plant and animal life is less diverse but hardier due to the arid nature of the region. Plant life, though not suitable for truly arid regions to the south, have evolved several defenses against water loss, as well as adaptions related to the yearly fires that burn through the region. Trees, such as the ponderosa pine, have thicker bark and do not bleed sap as profusely as trees to the west. Likewise, this thicker bark doesn't burn very easily. In fact, the ponderosa requires small brush fires to burn through, as their cones are opened by the heat of the passing fires. Likewise, plants such as the black sagebrush and cheatgrass occur frequently within the region, especially among the shorter western juniper. There are also many different species of wildflower.