There are many reasons to be thankful for trees. Besides being beautiful and giving shade, they provide habitats for animals. They are essential for the production of oxygen, which is needed for life on Earth. Trees supply important products like wood, paper, fruit and nuts. The livelihoods of more than 1.5 billion people worldwide depend on trees.
Unfortunately, only about one-third of Earth's surface is forested. Forests tend to fall into one of three types based on their location. There are boreal, temperate and tropical forests. Boreal forests are located the farthest north, while temperate forests grow in the mid-latitudes. Tropical forests are found closer to the equator. Countries with the largest forested area include Russia, Canada and the United States.
Forests are located in certain places because trees need specific conditions to thrive. Fertile soil, sunlight and rainfall are all important for tree growth. In places where the soil is poor, tree growth may be limited. The same is true of places that do not receive much sunlight or rainfall. Temperature also matters. Most trees do not do well in extremely hot or cold areas. Trees require conditions that are just right.
Even when trees do have the necessary conditions, they are not always safe. Trees can still be hurt by natural threats such as pests. One serious pest is the mountain pine beetle (Dendroctonus ponderosae). It has destroyed more than 260,000 square kilometers (100,000 square miles) of forest in the United States and Canada.
Another threat to forests is fire. Lightning strikes can set entire forests on fire, and heavy winds can quickly spread a fire. Forest fires have become an increasingly frequent problem in the western United States. Fires have always been part of the natural cycle in forests. Droughts and high temperatures have become more common, though. As a result, forest fires are becoming larger and more dangerous.
Less common problems include landslides, earthquakes and volcanic eruptions. In May 1980, Mount St. Helens erupted in the U.S. state of Washington. It sent out a shockwave and toppled thousands of trees. The eruption also triggered a series of volcanic mudflows. They ripped trees from the ground and scattered them across the land.
Human activities hurt forests as well. Some forests are cut down for wood, to make room for new trees or to simply clear the land. In other cases, forests are cut down to make room for farm animals. Tree removal is occurring in many regions, and it can be harmful to ecosystems. Cutting down forests reduces biodiversity. It destroys native habitats and forces animals to flee to find new shelter. Cutting down forests is also harmful to the native people who live in or near forests. Many of these people rely on trees for their food and shelter.
Trees do not grow equally around the planet. Some regions have more forests than others, and this inequality has important effects. In areas without forests, there are no forest products to be harvested and sold. People in those areas also miss out on secondary benefits. They miss out on money from tourism and fees from hunters going after animals. They also miss out on the simple pleasure of being in the forest.
