Still, the study suggests that tree planting could be a relatively cheap, incredibly effective way to begin combatting climate change.
This March 18, 2011 picture shows a dense forest of Douglas fir, madrone and oak on a steep hillside on federal forest land outside Ruch, Oregon. According to research published July 5th in the journal Science, a worldwide tree planting program that does not encroach on existing agricultural land or urban areas could remove two thirds of all the emissions that have been pumped into the atmosphere by human activities over the past 200 years, a figure the scientists describe as "mind-blowing".
"It is no doubt a monumental project, which is exactly the dimensions of the project of climate alternate".
"Every other climate change solution requires that we all change our behaviour, or we need some top-down decision from a politician who may or may not believe in climate change, or it's a scientific discovery we don't yet have", he told the Thomson Reuters Foundation. "I get uneasy when we start talking about managing billions of extra acres of land, with one goal in mind: to store carbon".
Planting trees to this magnitude would decrease Co2 levels in the atmosphere by approximately 25% - a pretty damning claim that even if we are nearly beyond the point of restoration, could significantly lessen the severity of climate change consequences in the future. "We now have definitive evidence of the potential land area for re-growing forests, where they could exist and how much carbon they could store".
The Crowther Lab website has a global map with advice on which types of trees and how many can be grown in gardens.
The researchers found Earth could support an additional 1.6 billion hectares more trees than it now has, to make for a total forest area equaling 4.4 billion hectares of continuous tree cover.
The study's calculations make sense, said Chris Field, an environmental scientist at Stanford University in California who also wasn't part of the study. That is 1.6 billion more than the now existing 2.8 billion hectares.
Right now there are estimated to be almost 44 million square km of forest cover on Earth, and there's enough room to add another 9 million square km of trees - a US-sized chunk of land - to sequester even more carbon. The greatest po-tential can be found in just six countries: Russian Federation (151 million hectares); the United States (103 million hectares); Canada (78.4 million hectares); Australia (58 million hectares); Brazil (49.7 million hectares); and China (40.2 million hectares).
The study is the first to quantify how many trees the Earth can support, where they could exist and how much carbon they could store.
The new data would help them refine their targets, he said.
In layman's terms, there is an area the size of the USA available for tree restoration. "It's not telling us at all how to implement it". "Restoring trees at [low] density is not mutually exclusive with grazing".
They also took into consideration the human-related factors that could skew the estimates, such as farmland or other non-forest green spaces.
But if there's a silver lining, it's that we know the solutions. Furthermore, Crowther Lab are supporting the creation of a global coalition that will bring targeted innovation to the opportunities and challenges identified by the Report. For one, a global tree-planting effort is somewhat impractical. This was made possible because of a unique global dataset of forest observations and the free mapping software of Google Earth Engine. They used this to approximate the natural level of tree cover in each ecosystem.