We at rapidlasso have long been big fans of the biomass and biodiversity work done by Greg Asner’s group and their Carnegie Airborne Observatory. They were, in fact, the earliest “power-users” of the BLAST extension of LAStools and helped finding all the bugs when rasterizing billions of LiDAR points collected during large-scale surveys in the Amazon into Digital Elevation Models (DEMs) with blast2dem. Below a video fly-through of some of the LiDAR they collected.
A few days ago, Greg Asner together with his colleagues Joseph Mascaro, Stuart Davies, Alex Dehgan, and Sassan Saatchi published a thought-provoking article called “These are the days of lasers in the jungle” which is essentially a “call for action” to map the world’s tropical forests with a fleet of airplanes outfitted with advanced LiDAR to rapidly and to accurately assess global forest carbon stocks.
Why would anyone want to do this? In order to properly quantify actual emissions savings for REDD+ (Reduced Emissions from Deforestation and Degradation). REDD+ is a tropical forest carbon accounting program of the United Nations Framework Convention on Climate Change that aims to compensate tropical countries for reducing carbon emissions from deforestation and forest degradation that account for roughly 10 percent of global greenhouse gas emissions. The key to implement such a program is the ability to accurately and affordably estimate the actual emissions savings and a worldwide LiDAR inventory of tropical forests will accomplish just that argues the paper. This “call for action” has since been picked up by Mongabay – a site that examines emerging trends in climate, technology, and finance on conservation and development.
Interesting is the price tag that they estimate, which is a fraction of the cost of a typical Earth observation satellite mission, They claim: “Our ambitious plan can be accomplished for far less than what we have already spent on avoided deforestation. Aircraft leasing, data collection and processing costs for 30 days of flying can reasonably be limited to USD 500,000 Using this monthly sampling unit, collecting at an average of 100,000 hectares per day, a fleet of ten aircraft could do the job in four years at USD 250 million, or just 5% of pledged REDD + funding.”
The authors state “The time has come for a brute-force effort to directly assess the carbon stock for all of the world’s tropical forests by 2020” because “airborne LiDAR is uniquely suited for this role because it can be collected, standardized, reported and verified in a simple manner by both a landholder and any third party”. Should such a campaign turn out to be a viable option to implement REDD+ we hope full waveform LiDAR – not just discrete returns – will be collected.
Waveform digitizers have become popular because they can capture the reflection of the emitted laser pulse with much more detail than a discrete return system. The intensity of the signal returning to the plane is digitized up to one billion times per second, giving a vertical resolution of one digitized amplitude each 15 centimeters. As this can capture the interactions between each laser pulse and the vegetation with much greater detail, it would seem that having full waveform instead of discrete returns will prove especially useful for biomass studies. A future blog post will talk about our own experiences of scanning tropical rainforest to produce full waveform LiDAR in PulseWaves format.
Another approach with a similar objective is being taken by NASA with their future GEDI space LiDAR. The Global Ecosystem Dynamics Investigation (GEDI) instrument will be the first to systematically probe the depths of the forests from space to reveal their 3D structure, as depicted in the artist’s concept below, and provide crucial information about the impact that trees have on the amount of carbon in the atmosphere. “One of the most poorly quantified components of the carbon cycle is the net balance between forest disturbance and regrowth”, said Ralph Dubayah, the GEDI principal investigator at the University of Maryland. “GEDI will help scientists fill in this missing piece by revealing the vertical structure of the forest, which is information we really can’t get with sufficient accuracy any other way”. The instrument will be built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Not sure about the price tag.
Until either of these projects become reality, “enjoy” this video by Carnegie Airborne Observatory of a 3D flyover that shows rapidly expanding palm oil plantations in the Peruvian Amazon rainforest that are contributing to deforestation.