Colombia years, the dead grasses have been burned simply to remove their useless mass. The result of burning is that most trees are killed, leaving an open environment in which grasses thrive. Savannas are natural pasturelands, but overgrazing can lead to soil erosion. These grasslands are by no means tree free. Trees often grow along the banks and floodplains of the stream courses, where they are protected from fires. Drought-tolerant species of palms and other trees also grow scattered about the open plain. As noted, the sweeping grasslands of the Oriente make up Colombia’s main cattle-ranching area, although extensive areas are overgrazed. Desert plants grow in the tierra caliente where rainfall is too low to support savanna grasses. The Guajira Peninsula is such a location. Plants there are able to survive because they need only small amounts of nutrients and water. Desert grasses grow in widely spaced clumps. Certain small bushes are xerophytes (from Latin for “dry plants”). They have the ability to reduce moisture loss through leaves and stems. Other plants, such as cacti and agaves, are succulents. They have special “spongy” cells that store precious water. As in all dry lands, the amount of rainfall is meager, so farming is difficult, even in the most favorable localities. Some of the country’s poorest farmers eke out a living in the arid Guajira region. The tierra templada is pleasant for plants because the mod- erate elevations of 3,000 to 6,000 feet (915 to 1,829 meters) compensate for the high temperatures of the low latitudes. A lush evergreen cloud forest grows in this zone. Here, the dense forest creates a closed canopy. Below, colorful orchids, delicate ferns, and thousands of other plants grow. Vines hang from many trees, as do the dangling roots of epiphytes (plants that gain their nourishment from the air). Alluvial (stream) deposits create fertile soils in the valleys. The agreeable climate and fertile valleys of the Andes support Colombia’s densest populations. Geographers refer to this region of South America as the “Coffee Zone” because coffee is a typical commercial crop grown there.