Much of the wildlife on earth could not exist without trees. In addition to releasing oxygen into the air for animals to breathe, trees provide homes and food for many animals. Trees are also important because they provide shelter from the wind, aid in preventing soil erosion, and enrich the soil with their decaying leaves.

Trees have many commercial uses. Their wood yields thousands of products, including paper, medicines and other chemicals, and lumber. Trees also provide food, such as fruits, spices, and nuts. Bark from the roots of the sassafras yields a tea and oils, and various chemicals are derived from the roots of the longleaf pine. Some tree bark yields such substances as cork, tannins, and cinnamon, as well as various kinds of drugs and dyes. Some leaves, such as those of the palmyra palm, provide fibers that are woven into twine, rope, and mats. Fluids from trees yield many useful products, including rubber, maple syrup, and turpentine.

Trees are also valuable for ornamentation. They line streets and adorn gardens, making them cooler and more comfortable in summer by providing shade. Among favorite shade trees in the United States are the locust, oak, elm, beech, linden, maple, birch, willow, ash, and sweet gum. Trees cultivated for their ornamental flowers include the tulip tree, horse chestnut, locust, crab apple, and catalpa.