There are many reasons to be thankful for trees. Besides being beautiful and giving shade, they provide habitats for animals, and they are essential for the production of oxygen, which is vital 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: boreal, temperate and tropical. Boreal forests are located the farthest north, temperate forests grow in the mid-latitudes and tropical forests are found closer to the equator. Countries with the largest forested area include Russia, Canada and the United States.
Forests are concentrated in particular places because trees require specific conditions to thrive. Fertile soil, nutrients, sunlight and rainfall are all important for tree growth. In places where the soil is poor, tree growth may be stunted or not occur at all. For instance, trees atop mountains are typically much smaller than those at lower elevations, where the soil is better. Likewise, places that do not receive much sunlight or rainfall typically have few trees. Temperature also matters—most trees do not do well in extremely hot or cold areas. Trees are a bit like Goldilocks: They want conditions that are just right.
Even when trees do have the necessary conditions, they can 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. The mountain pine beetle kills trees by clogging their connective tissues.
Fires and Tree Removal are Harmful to Forests
Another threat to forests is fire. Lightning strikes from thunderstorms can set entire forests ablaze, 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. However, as drought and high temperatures have become more common, forest fires are becoming larger and more dangerous.
Less common problems include landslides, earthquakes and volcanic eruptions. In May 1980, the explosive eruption of Mount St. Helens in the U.S. state of Washington sent out a shockwave. It toppled thousands of trees and stripped others of their branches. The eruption also triggered a series of volcanic mudflows. They ripped trees from the ground and scattered them across the land.
Human activities take a serious toll on forests. Some forests are cut down for timber, to make room for new trees or to simply clear the land. In other cases, forests are cut down to make room for livestock. Tree removal is occurring in many regions, and it can be devastating for ecosystems. Swaths of razed forest are more likely to experience erosion because tree roots are no longer holding the soil in place. Furthermore, 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 around the globe who live in or near forests. Many of these people rely on forests for their food and shelter.
Trees are not distributed equally around the planet. Some regions have more forest resources than others, and this inequality has important effects. To begin with, in areas that lack 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 large animals. Aside from this, they also miss out on the simple pleasure of being in the forest.