The researchers calculated that under the current climate conditions,
Earth’s land could support 4.4 billion hectares of continuous tree
cover. That is 1.6 billion more than the currently existing 2.8 billion
hectares. Of these 1.6 billion hectares, 0.9 billion hectares fulfill
the criterion of not being used by humans. This means that there is
currently an area of the size of the US available for tree restoration.
Once mature, these new forests could store 205 billion tonnes of carbon:
about two thirds of the 300 billion tonnes of carbon that has been
released into the atmosphere as a result of human activity since the
Industrial Revolution.