Savanna is a grassland-type habitat that covers large areas of Southern Guam. It develops on volcanic soil and usually non-flat areas. Savanna is dominated by dense, tall, sharp swordgrass (Miscanthus). Also present are Dimeria and other grasses, and some scattered Casuarina and Pandanus trees. The savanna is often swept with uncontrolled, often deliberately started, grass fires. As a result, susceptible trees are killed and grass species expand their total area. Currently, savanna covers more than a fifth of all land in southern Guam.