Tree Image Gallery
Tree Image Gallery

Forests, like this one in France, cover 30 percent of the Earth. See more pictures of trees.

Marcel Mochet/AFP/Getty Images

Trees make o­ur lives more pleasant. They're beautiful to look at, and they can provide sh­ade or a good hideout. Forests cover 30 percent of our planet, concentrated mostly in 10 countries: the United States, Canada, the Russian Federation, Brazil, China, Australia, the Democratic Republic of Congo, Indonesia, Peru and India [source: United Nations Environment Programme].

Tree Image Gallery

That may sound like a lot of forest, but worldwide, our forests are disappearing. About 13 million hectares of forest -- an area roughly the size of Greece -- disappear every year. Deforestation happens because of population growth and increasing agricultural and industrial demands; trees are cut down to make room for new developments.

Why does it matter if trees are planted or cut down? Trees provide us with wood, fuel, food, medicine, latex and other products used in our daily lives. They also affect our climate. No, they can't make snow on a sunny summer day, but their very existence -- or removal -- makes a difference.

Climate isn't the same as weather. While weather is short-term, like the five-day forecast on the evening news, climate is the weather pattern over a long period of time, usually 30 years. And the climate of our planet is warming -- heating up by approximately 1 to 1 1/2 degrees in the past century [source: The Weather Channel].

In the next section, let's look at the ways trees positively and negatively affect our climate, and, in turn, our weather.