1 August 2017

Scanning trees with laser beams

The Science Festival is back at Kew Gardens this weekend, 4–6 August! Science Festival intern Mair Bosley delves into the science behind one of our fantastic festival stalls, to help us see the wood for the trees.

By Mair Bosley

Lidar scan of trees

After the success of the Wakehurst Science Festival in July, the upcoming Kew Science Festival is sure to go down a storm, and I’m even more excited now I’ve seen what our scientists are bringing into the gardens.

I spoke to Kew scientist Amanda Coopera, in the Bioinformatics and Spatial Analysis team, to discuss the future of tree science and the technology that found Borneo’s tallest measured trees – at six sperm whales high! 

What is LiDAR?

LiDAR, which stands for Light Detection and Ranging, is cutting edge technology that enables scientists to accurately measure the height, volume, and structure of trees and forests, with up to 90% higher accuracy than traditional methods. The name originated as a mix of ‘light’ and ‘radar’ and, as it suggests, uses a high frequency laser beam to record distances. Using the same principle as bats with echolocation, the laser beams from the device and bounces back from the target. The LiDAR sensor measures the reflected pulses and calculates how far the laser has travelled. Once the scanner has sent out thousands upon thousands of pulses, it can use this information to build a 3D image of the tree and its surroundings. 

In 2016, a team from the Carnegie Institute used airborne LiDAR technology to measure trees in the heart of Borneo. They discovered the tallest tropical tree which is a behemoth measuring 94.1 metres. This surpassed measurements made by researchers from the University of Cambridge, who previously recorded trees in Borneo measuring 89.5 metres, using laser scanning technology. With such precise measurements, and the availability of airborne laser scanners, we can set our sights on LiDAR tree mapping becoming one of the most important techniques in the field.

Why is this important?

This improved ability to measure and create accurate 3D images of trees has important significance. As the world’s attention is increasingly focussed on habitat destruction, increasing CO2 levels and climate change, accurate and efficient tree measurement techniques have become vital for allowing science to progress.

Trees play a vital role in removing CO2 from the atmosphere and converting it into stored carbon, but in order to measure how much carbon is stored in a tree, we need to know the tree’s mass. With the volume measurements from a laser scanner and an idea of the tree density, we are able to make that calculation. Before this technology, the only way to determine a tree’s mass, beyond estimation, was to chop it down and weigh it. Measuring carbon storage through LiDAR is incredibly useful for conservation planning and tree valuation. Schemes like REDD+ (Reducing Emissions from Deforestation and Degradation), for example, use carbon storage as a currency to foster sustainable forest management.

As well as volume, a measure of how complex a tree’s structure is can be very important for conservation measures, as high structural complexity often means high biodiversity and many habitat niches for other species. This can be very hard to estimate visually so LiDAR scanning provides reliable data to work from, to determine the most important habitats in a forest.

Kew researchers are starting to deploy this technology to the field to provide better information about critical habitats in support of conservation. Kew’s terrestrial based LiDAR has been used at a number of sites in Peru, focusing on heavily degraded desert ecosystems along the Peruvian coast.

We can also measure human impacts on habitat by taking measurements of trees and comparing them over space and time. This can help to work out the best way to manage human and wildlife interactions in the future to minimise damage to ecosystems and species.

At the Kew Science Festival

With the help of our scientists at Kew, we will have our very own LiDAR laser scanner set up at the Science Festival. You will get the chance to see it in action, creating 3D images of three target trees in the gardens. You will also have the opportunity to measure trees yourself – can you be as accurate as the laser scanner? Construct a clinometer the old-fashioned way and find out.

There will also be some exhilarating drone footage from the tree tops so you can have a birds-eye view of the trees, getting a taste of what it is we are trying to measure. Then you can experience a fly-around with the LiDAR data to see how it compares. Be one of the first to discover this cutting edge technology, and prepare to be impressed!

Read & watch