The planet of the trees has given way to the planet of the apes. The Earth has lost more than half of its trees since humans first learned how to wield the axe, scientists have found.
A remarkable study has calculated that there are about 3 trillion trees on the planet today but this represents just 45 per cent of the total number of trees that had existed before the rise of humans.
Using a combination of satellite images, data from forestry researchers on the ground and supercomputer number-crunching, scientists have for the first time been able to accurately estimate the quantity of trees growing on all continents except Antarctica.
Previous guesses at the global number of trees were in the range of 400 billion, or about 61 trees for every person on Earth. However, the latest, more accurate study, based on 400,000 estimates of tree densities around the world, puts the total at 3.04 trillion, or roughly 422 trees per person.
However, although the actual number of trees may be about eight times higher than previously thought, the scientists warned that we are cutting them down at the rate of about 15 billion a year, with the highest losses in the tropics where some of the oldest and biggest trees live.
The scientists calculate that there are 1.39 trillion trees growing in tropical and sub-tropical forests, about 0.61 trillion in temperate regions such as the US and Europe and 0.74 trillion in the boreal forests in the higher, more northerly latitudes of Canada and Siberia.
Mapping trees globally will help us to understand the critical role they play as part of Earth’s life-support system, explained Thomas Crowther of Yale University in New Haven, Connecticut, the lead author of the study published in the journal Nature.
“Trees are among the most prominent and critical organisms on Earth, yet we are only recently beginning to comprehend their global extent and distribution,” Dr Crowther said.
“They store huge amounts of carbon, are essential for the cycling of nutrients, for water and air quality, and for countless human services. Yet you ask people to estimate, within an order of magnitude, how many trees there are and they don’t know where to begin,” he said.
“I don’t know what I would have guessed, but I was certainly surprised to find that we were talking about trillions,” he added.
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