This is the kind of news that makes us groan. A new study of arboreal density around the globe indicates humans are directly responsible for killing almost half the trees on the planet. This latest report confirms the devastation we already knew, but in a very real way, since this study is the first of its kind to be derived from actual data, giving us a more accurate picture of the Earth’s forests than ever before.
Like many scientific reports, there is good news and bad news in this one, which was just published in the journal Nature. This study is the first-ever data-driven global tree census, so it provides the most accurate count of trees to date. Researchers calculated there are some 3.04 trillion trees on Earth today, which breaks down to approximately 422 per person. That’s good news, because it surpasses previous estimates that put the figure at just a fraction of that. The bummer, though, is that the current number of trees represents a 46 percent decline since humans started cutting them down.
Arriving at the new tree density figures was a feat partly of mathematics and partly of wizardry. Researchers collected 429,775 ground-sourced measurements of tree density from every continent except Antarctica (because, you know, there are no trees there). They combined that information with satellite data on climate, topography, and human land use. The resulting models predicted tree density around the globe down to a single square kilometer.
Comparing those tree density predictions with spatial maps of forest loss, the researchers calculate that humans are removing approximately 15.3 billion trees each year, with the highest rates of decline happening in the tropics. Forest regrowth accounts for a little more than 5 billion trees per year, making for a net loss of around 10 billion trees annually. That’s a lot of tree killing we’re doing, people.
Images via Shutterstock and Crowther, et al 2015