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Everyone knows lungs are important to people. Do you know what are the lungs of the earth? Forests. The earth can’t breathe without them. It needs      forests to remove carbon dioxide from the air     to make oxygen. In many     , such as New Zealand, Canada, and Brazil, forests were cut down to      wood to build houses. Many young volunteers around the world      working in their holidays to plant new trees to replace them.
These young people face many       when they plant new trees. The weather may be hot and dry or it may be cold and wet. There are often many insects       bite these planters on their legs, arms, and faces while they work. They carry heavy bags of small trees, and working in the mountains can be dangerous.
Tree planters are     the world. They plant different types of trees so that birds and animals can live in the forests. Even though tree     is difficult, they love their work. They believe that in 50 years their    trees will become beautiful forests.