Forests Cover 9 Percent More Of Earth Than Thought

You think it would be pretty hard to miss a forest, but it turns out that there are far more trees covering the planet than previously thought. Researchers have found that globally, forest cover is 9 percent higher than earlier estimates.

These new forests, which are enough to blanket two thirds of Australia, have been found hiding in plain sight. While tropical forests may be well studied, scientists turned their attention to the oft overlooked dryland forests. In these regions, more water is lost to evaporation and transpiration of the trees that is gained in rainfall, meaning that forests are less dense than their tropical counterparts closer to the equator.

Traditionally it has been pretty difficult to get an idea of how much forest there is covering the worlds dryland. This is because previous satellite images have only had a resolution of somewhere in the region of tens of meters to each pixel. As the forests in these regions are typically quite sparse, the low resolution has meant that its been tricky to tell the difference between, say, a shadow and a tree.

Jean-Franois Bastin et al. 2017

But by using a new set of ultra-high resolution satellite images provided by Google Earth, a team of researchers from 15 institutions have been able to effectively analyse over 200,000 dryland plots, each with a resolution of around one meter (3.3 feet) to one pixel. This has given them a much better idea as to the true extent of dryland forests, and they found that they covered 40 percent more land than previously thought, bumping up the total forest cover globally by an impressive ninepercent.

After discovering what they thought was new woodland using the satellite images, they then cross referenced it with field information to make sure they were correct. On every single permanently inhabited continent forests were found to cover more dryland than thought. This was most prominent in Africa where the study, published in Science, doubled the amount of known dryland forest.

The addition of some 467 million hecatres of woodland is thought to have a significant impact on our understanding of carbon cycling, which in turn has a knock on effect on the worlds carbon budget. The researchers estimate that with the number of trees in these forests, it will increase the total global forest carbon stocks by between 15 and 158 gigatonnes of carbon, a not so insignificant increase of between two and 20 percent.

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