Plant a trillion trees to fight global warming, urge scientists
The most effective way to fight global warming is to plant a trillion or more trees, according to a study.
And there's enough room, Swiss scientists say.
Even with existing cities and farmland, there's enough space for new trees to cover nine million square kilometres, they reported in journal 'Science'. That area is roughly the size of the United States.
The study calculated that over the decades, those new trees could suck up nearly 750 billion tonnes of heat-trapping carbon dioxide from the atmosphere.
That's about as much carbon pollution as humans have spewed in the past 25 years.
Much of that benefit will come quickly because trees remove more carbon from the air when they are younger, the study said. The potential for removing the most carbon is in the tropics.
"This is by far - by thousands of times - the cheapest climate change solution" and the most effective, said study co-author Thomas Crowther, a climate change ecologist at the Swiss Federal Institute of Technology in Zurich.
Six nations with the most room for new trees are Russia, the US, Canada, Australia, Brazil and China.
Before his research, Dr Crowther figured that there were other more effective ways to fight climate change besides cutting emissions, such as people switching from meat-eating to vegetarianism.
But, he said, tree planting is far more effective because trees take so much carbon dioxide out of the air.
The researchers used Google Earth to see what areas could support more trees, while leaving room for people and crops.