2 September 2015, Theguardian news - Scientists have already calculated how many fish there are in the sea (230,000 species), and how many species there are on the planet overall (8.7m). Now they have had a crack at counting all of the world's trees.
Using a combination of satellite and ground measurements, researchers estimated that there are just over 3tn trees on the planet, over seven times as many as the current, non peer-reviewed reckoning that relied on satellite images alone.
New assessment has found people are now responsible for the loss of 15bn trees a year. Photograph: David Sillitoe for the Guardian
But people are having an "overwhelming" impact on the world's forests, according to the international team from 15 countries. Human activities have led to the loss of nearly half the world's trees (45.8%), the study found.
Today, people are responsible for the loss of around 15bn trees a year due to deforestation and demand for farmland, a figure that the authors said was "considerably higher" than just a century ago.
"The scale of the human impact [we found] was astronomical. The number of trees cut down is almost 3tn since the start of civilisation," said Thomas Crowther of Yale University, the lead author of the study, published in the journal Nature on Wednesday.
"I didn't expect human activity to come out as the strongest control on tree density across all of the biomes [habitat types]. It was one of the dominant regulators of the number of trees in almost all of the world. It really highlights how big an impact humans are having on the Earth at a global scale," he said.
