LiDAR shows increasing usefulness in forest monitoring


Measuring how much carbon is stored in the world’s forests is a challenging task and, unlike measuring deforestation, which may be done using commonly available satellite measurements, can be relatively resource-intensive, especially to achieve high levels of accuracy. However, a new study from the National Academy of Sciences has raised the possiblity of more widespread use of aerial and satellite data, making the task easier. LiDAR (Light Detection and Ranging) data from a survey plane was combined with satellite and ground data to build a forest map covering 11m square acres. LiDAR technology is able to measure tree height and this data can then be used to construct 3D maps of forest carbon stock. According to Greg Asner, lead author of the study, told Reuters: ‘What we’re showing here for the first time is an ability to not only map the carbon … that is in the forest, but also use a technique that allows us to estimate the emissions…In terms of an international climate treaty, that’s the big one.’

Ruth DeFries, from Columbia University, points out that the level of detail makes the survey ‘a wonderful demonstration of the ability to monitor carbon stocks, which is required to implement policies such as REDD’, reports the New York Times.

Meanwhile another LiDAR unit, this time mounted on NASA’s ICEsat satellite, has been used to produce the first map of global canopy heights. The process, which took seven years and covered 2.4 per cent of the earth’s forests, generated vertical cross-sections of various forests. Michael Lefsky, from Colorado State University, then merged this dataset with global data from the Moderate Resolution Imaging Spectroradiometer, an instrument mounted on board two other NASA satellites. The map leads the way for more detailed survey techniques in the future, as more sensor technology is developed.

Laurent Rathborn, London.

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