Scientists divide the Earth’s land into what are called vegetation regions. These areas have distinct types of plants, soil, and weather patterns. Vegetation regions can be divided into five major types: forest, grassland, tundra, desert, and ice sheet. Climate, soil, the ability of soil to hold water, and the slope, or angle, of the land all determine what types of plants will grow in a particular region.
Forests are areas with trees grouped in a way so their leaves, or foliage, shade the ground. Forests can be found just about anywhere trees can grow, from below sea level to high in the mountains. From tropical rain forests near the Equator to boreal forests in cold climates close to the Arctic Circle, different types of forests can be found all over the world.
One way to classify different types of forests is by the type of trees a forest has. Deciduous forests have trees with green leaves that change color in the fall and drop altogether in the winter. Trees that are common in deciduous forests are oak and maple. The northeastern United States is covered in deciduous forest, and tourists flock to the area every autumn to experience the orange, yellow, and red leaves blanketing the region.
Evergreen forests have trees with leaves that stay green all year long. One of the places evergreen forests can be found is on the opposite side of the North American continent—in the Pacific Northwest, which includes the Canadian province of British Columbia and the U.S. states of Washington and Oregon. The Pacific Northwest is full of evergreen trees like fir.
Sometimes forests are classified by the type of leaves on their trees. Trees in broad-leaved forests have wide, flat leaves. Tropical rain forests are a type of broad-leaved forest. Tropical rain forests, such as Brazil’s Amazon Basin rain forest, are found near the Equator. They contain more than half of the world’s biodiversity, or variety of plant and animal species.
Coniferous forests have trees with cones and needles instead of leaves. Coniferous forests have the tallest (coast redwood), largest (giant sequoia), and oldest (bristlecone pine) trees in the world.
Many forests are mixed, meaning they have both broadleaf and coniferous trees. The eucalyptus forests of Australia are mixed forests, for instance. The evergreen eucalyptus trees are mixed with deciduous trees like beech.
Grasslands are, as their name suggests, flat and open areas where grasses are the dominant type of vegetation. Grasslands can be found on every continent except Antarctica.
Climate plays a role in the type of grassland you get. In cool, mild climates, like northwest Europe, grasslands are dominated by tough vegetation, such as oats, that thrives all year. Some of these grasses are so tough and hardy that they are considered weeds.
In warmer climates, seasonal vegetation survives better. Temperate grasslands exist where there are seasonal variations in temperature over the course of the year: hot summers and cold winters. Different grasses thrive in different temperatures here. Temperate grasslands exist from the prairies of North America to the veld, or rural grassland, of South Africa.
Tropical grasslands are called savannas. They do well in weather that is warm year-round and usually pretty dry. The most famous savannas are in Africa. Serengeti National Park, in Tanzania, has three distinct types of savanna grassland: long grass, intermediate grass, and short grass. This part of the Serengeti is known as the Serengeti Plains, and it supports wildlife from aardvarks to zebras.
Grasslands are important for milk and dairy production; dairy cows are happiest, and most productive, in areas in which they can munch on grass all day.
Tundra is an area where tree growth is difficult because of cold temperatures and short seasons. Vegetation in tundra is limited to a few shrubs, grasses, and mosses. Scientists estimate roughly 1,700 different species live in the tundra, which isn’t much compared to forests and grasslands. The ground is often too cold for plants to set down roots, and without plants, few animal species can survive.
There are two types of tundra: alpine tundra and arctic tundra. Alpine tundra is separated from a forest vegetation region by the tree line, the area beyond which conditions are too harsh or cold for tree growth. The weather in alpine tundras is cold, snowy, and windy. Most of the Tibetan Plateau, the so-called “roof of the world” located in Tibet, China, and India, is alpine tundra. Animals like mountain goats live in this vegetation region.
Arctic tundra occurs in the far-northern hemisphere of the Earth. It has a bare landscape and is frozen for much of the year. Here, the tundra can include permafrost, or soil that is permanently frozen. Russia and Canada have huge areas of arctic tundra. During the summer, the permafrost thaws just a bit, allowing some plants to grow in the wet, marshy ground. You won’t find many mammals in the arctic tundra, but thousands of insects and birds show up every year and enjoy the marshes before they freeze. Among the few mammals that actually thrive in the arctic tundra are caribou and polar bears.
Deserts have almost no precipitation, or rainfall. In fact, deserts are specifically defined as areas with an average annual precipitation of less than 10 inches per year. Deserts usually have really high daytime temperatures, low nighttime temperatures, and very low humidity.
Desert soil is often sandy, rocky, or gravely. Plant life is highly specialized to adapt to these coarse, dry conditions, with long roots, small leaves, stems that store water, and prickly spines that discourage animals from touching or eating them. Cactuses, which are native to deserts in North and South America, are an example of this kind of plant. Despite the barren look of hot deserts, they are full of animal life. Most desert animals, such as lizards or snakes, are nocturnal, meaning they are active at night. Nocturnal animals take advantage of the cooler nighttime temperatures of the hot desert.
Not all deserts are hot and sandy, however. The largest desert in the world is the Antarctic Desert, which takes up most of the continent of Antarctica. In the Antarctic Desert, ice sheets cover barren rock. Few animals can live in the Antarctic Desert. Those that do are often microscopic, such as lice.
The interesting thing about the ice sheet “vegetation region” is that there really isn’t any vegetation there at all! An ice sheet is a large stretch of glacier ice that covers the land all around it for more than 50,000 square kilometers (20,000 square miles). Currently, the only ice sheets are in Antarctica and Greenland. Don’t confuse the ice sheets, called polar ice caps, with other ice shelves or glaciers; an ice sheet is much, much bigger.
Ice sheets are important research sites for scientists. The Antarctic ice sheet is a record of Earth’s atmospheric changes. By looking at layers in the ice, scientists can keep track of different levels of pollution or volcanic gases in the atmosphere. The 1883 eruption of the Indonesian island volcano of Krakatoa can be located and dated by the distinct air bubbles in the Antarctic ice sheet, for instance.
Scientists are also studying ice sheets to measure the rate of melting ice. Parts of the Greenland ice sheet were once thought to be permanent, but they are now melting at a fast pace.