More than 3 trillion trees exist on Earth – roughly 422 per person – but the total number of trees has plummeted by 46 per cent since the start of human civilisation.The new estimate of more than 3 trillion trees on Earth is about seven and a half times more than some previous estimates of 400 billion. An international team of researchers mapped tree populations worldwide at the square-kilometre level using a combination of satellite imagery, forest inventories, and supercomputer technologies.