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Forests: Facts

What is a Forest?

Green Forest

How do you define a forest? A forest is a complex community of life in which trees are the dominant life-form. They can also have a huge population of woody plant life. Forests cover almost 1/3 of the earth's land surface. Five thousand years ago they covered over half the earth. Forests have been and still are important for many reasons.

Why are forests important? Healthy forests filter water, remove air pollution, absorb carbon, and provide homes for wildlife and plants. They prevent soil erosion and play a role in climate control. Forests are places of beauty and recreation, provide food, fuel and medicine for people all over the world. Probably most importantly, forests produce large amounts of oxygen that we need to breathe.

Forests are made up of three growth layers. The thick top layer is called the canopy. This is where the tops of the trees meet to form a roof that does not allow much sunlight to reach the layers underneath.

The layer just below the canopy is known as the understory, also called the lower canopy. Here small trees and bushes live. They receive very little light due to the canopy. They have been lucky to grow to this size due to the limited sunlight.


The forest floor is the third and lowest layer of the forest. Here you can find rich soils, small plants and animals, and grasses. Wildflowers can grow here too. The grasses and wildflowers can make good food for the animals that live in the forest. New little trees that have started from dropped seeds may or may not grow to maturity, depending upon the amount of sun and rain that reaches them through the canopy and understory.

Forests have different environments, depending upon the climate where they grow. There are three basic forest types in the world — tropical rainforests, temperate forests, and boreal forests. Kinds of trees, amount of rain, and animals vary for each type of forest.

You can learn more about the forests of the world at The Forest Biome.

Tropical Rain Forests

Rain Forest

Tropical rain forests (also spelled rainforests) occur near the equator. They have only two seasons — rainy and dry — and no winter. Rain forests are so-called because it rains very frequently. In some forests it can rain every day. In fact, in a number of rain forests, the rain is generated from the moisture and the plants in the forest itself and it cycles around and around. Some of the rain may never reach the ground but will lay on the leaves of the understory.

There are more types of trees in a rain forest than in any other area of the world. Insects are the largest group of inhabitants in the rain forest. Rain forests have their own populations of plants and animals that can vary from forest to forest. Sometimes it can vary within the same forest from area to area.

Learn more about tropical rain forests at

Temperate Forests

Forest Road

Temperate forests occur in eastern North America, northeastern Asia, and western and central Europe. They also occur south of the Equator. They have 4 seasons including winter.

Temperate forests consist of deciduous trees and sometimes evergreens. Deciduous trees include maple, ash, oak, hickory, beech, and birch. They have colorful leaves which fall to the ground each fall. Evergreens, such as spruce and fir, have needles instead of leaves. They never lose their needles, which have a special waxy coating to protect them in winter.

Expansive deciduous forests once covered most of the eastern half of what is now the United States, from northern New England to central Florida, and west to the Mississippi River. But much of this temperate climate forest has been cut down to clear land for crops and cities.

Learn more about temperate forests at Kids Do Ecology and NASA.

Boreal Forests

Winter Forest

Boreal forests, also known as taiga, occur between 50° and 60° north latitudes. Boreal forests can be found in Eurasia — Siberia and Scandinavia — and North America — Alaska and Canada.

Taiga is the Earth's largest land habitat, covering about 17 percent of the planet's land. Summers are short, moist, and moderately warm. Winters are long, cold, and dry. Precipitation is usually snow. Taiga is filled with evergreens such as pine, fir, and spruce. Fauna include woodpeckers, hawks, moose, bear, weasel, lynx, fox, wolf, deer, hares, chipmunks, shrews, and bats. The boreal forests are in danger of extinction due to over logging.

More about boreal forests at BluePlanetBiomes, Kids Do Ecology and NASA.

Idaho Forests

Pine Tree

More than 60% of Idaho is covered in forestland. Idaho's forests are found in the mountain regions. These forests are largely conifers or pine trees. Idaho's state tree, the Western White Pine, is found in the forests of northern Idaho. But a few deciduous trees, such as aspen or birch, can also be found in Idaho's forests.

Forests are found in high altitudes where snowpack and rain feeds the roots enough moisture to sustain these giant life forms. A 100 foot tall tree requires more than 11,000 gallons of water in one growing season. This water is recycled back into the environment when the tree releases oxygen and water vapor.

One large tree can provide a day's oxygen for four people!

Idaho is host to all or parts of 16 National Forests. To learn more about each of them, visit the Idaho Digital Atlas.

Forest Fires


One of the greatest threats to forests is fire. Fire can destroy not only the lives and homes of the forests' plants and animals, but those of the people who live nearby.

Can a forest ever recover from a fire? Yes it can, but, it can take long time! An average forest of trees is about 70–100 years old. And trees in some forests can be 4,000–5,000 years old.

Find out more about forest fires at the Science Trek Wildfire site and at the ESA.

What Forests Give Us

  • Oxygen — we need this for breathing every day
  • Ability to absorb carbon from the atmosphere
  • Clean air and water
  • Wood for furniture, houses and paper
  • Medications to treat cancer and asthma
  • Foods such as mushrooms and berries
  • Ability to regulate air temperature
  • Ability to affect local weather
  • Homes for animals
  • Recreation
  • Peaceful, relaxing setting
  • Ability to store water
  • Fuel

Want to learn more about trees? Check out Science Trek's website on Trees.

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