In the northern lands close to the Arctic, and on the upper slopes of high mountains all over the world, a unique biome called the tundra is found. The word tundra comes from a Finnish word "tunturia," which means barren land. In this cold, dry, windy region where trees cannot grow, the often bare and rocky ground will support only hardy, low-growing plants, such as mosses, heaths, and lichens (LY-kens), which give it a greenish-brown color. During the brief spring and summer, flowers burst into bloom with the warmth of the Sun, dotting the landscape with color.

Tundra covers about 20 percent of the Earth's surface. Although almost all tundra is located in the Northern Hemisphere (the half of the...