Scientists are aksing: What is the best way to fight climate change? A new study says: Plant many trees; one trillion trees, maybe more. Swiss scientists say there is enough room for that many trees. In their report in the journal Science, they say there is enough space on the earth, which could cover nine million square kilometers, an area the size of the United States.
Trees take carbon dioxide（二氧化碳）out of the air, and in return, put oxygen back into the air. The study estimated that over a long period of time, the trees could take in almost 750 billion tons of carbon dioxide from the atmosphere. That is about as much carbon as humans have put into the atmosphere in the past 25 years. What is so bad about carbon dioxide? The gas traps heat, causing temperatures to rise.
Much of the gain from planting trees will come quickly because trees remove more carbon from the air when they are younger, the researchers said. The place that has the best possibility for removing the most carbon is the tropics—the area close to the equator. This method would also have the lowest cost, says the study co-author Thomas Crowther, a climate change ecologist at the Swiss Federal Institute of Technology in Zurich. This is by far, the cheapest and the most effective climate change solution, he said. The six nations with the most room for new trees are Russia, the United States, Canada, Australia, Brazil and China.
Before his study, Crowther thought that there were other more effective ways to fight climate change besides cutting emissions（排放）. For example, people could change their diets by no longer eating meat. But, he said, tree planting is far more effective because trees remove so much carbon dioxide from the air.
