Ever glanced up at an enormous tree and pondered at the numbers behind such a vast organism? How heavy it is, or how long all those branches are? Developments in laser scanning technology emerging from University College London’s Department of Geography – in collaboration with Oxford University, Sonoma State University in California, Ghent University in Belgium, and Wageningen University in the Netherlands – is helping answer these questions.

Previously, the best estimates for the full weight of selected trees required either actually cutting them down, or getting tied up in knots while undertaking various crude methods of diameter measurements. Rooted in hard science, this new terrestrial scanning approach instead uses laser equipment costing between £75,000 and £150,000, firing hundreds of thousands of pulses per second in order to pinpoint branches to an accuracy within millimetres from a range of nearly one kilometre. This then generates accurate 3D models.

One key aim of the research is to branch out into measuring how much carbon particular trees will consume during their full lifecycle, which is immensely informative in understanding the impact their presence (or otherwise) has in limiting the worst impacts of climate change. Many tropical trees around the world have been measured in this way, including in Brazil and Borneo, as well as giant sequoias in California. A 45m tall Moabi tree in Gabon was estimated to weigh around 100 tons, making it the largest tropical tree yet measured.

California sequoias (Image: Shutterstock)

The technology was also demonstrated last year during the BBC One show Judi Dench: My Passion for Trees, where detailed scans revealed the 200-year-old oak in Dench’s garden to weigh around 25 tons and contain over 260,000 leaves – equivalent to the surface area of three tennis courts.

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