Despite deforestation that is hastening the pace of climate change and causing wildfires to rage out of control across the planet, there are still billions of acres available to plant new trees.
That's according to The Crowther Lab of ETH Zurich, which for the first time mapped out 2.2 billion acres of land around the globe that has the conditions for reforestation and could capture about two-thirds of carbon emissions caused by humans.
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Billions of acres available for reforestation
In a research report published in journal Science, the researchers led by Jean-François Bastin, a postdoctoral student at Crowther Lab, concluded there is enough land to support 4.4 billion hectares of trees, up from the 1.6 billion hectares in existence today. The researchers estimate there are 0.9 billion hectares that could act as canopy cover, storing 205 gigatonnes of carbon in areas that would naturally have woodlands and forests.
In order to map out where trees can be planted, the researchers built models using direct measurements of tree cover from protected areas where vegetation cover has largely been unaffected by humans.
By studying the entire range of environmental conditions, they were able to come up with a natural tree cover estimate across the globe which allowed them to come up with a predictive understanding of the potential of tree coverage without human activity.
Researchers look at natural tree coverage
"The focus on protected areas is intended to approximate natural tree cover. Of course, these regions are not entirely free of human activity, presenting slightly lower tree cover than expected in some regions or higher tree cover than expected in other regions because of low fire frequency, but these ecosystems represent areas with minimal human influence on the overall tree cover," wrote the researchers. "We then used a random forest machine-learning approach to examine the dominant environmental drivers of tree cover and generated a predictive model that enables us to interpolate potential tree cover across terrestrial ecosystems. The resulting map—Earth’s tree carrying capacity—defines the tree cover per pixel that could potentially exist under any set of environmental conditions, with minimal human activity."
Countries don't have a good idea of how much land is available
The researchers said their work underscores the need for better country-level forest accounting, which is necessary for developing effective reforestation strategies. They noted that about 10% of countries have committed to restoring an area of land that exceeds the total area for restorations by a lot while 43% of countries have vowed restoration in areas that are less than 50% of the available area.