At this very moment a shower of laser pulses is reaching Earth from the International Space Station.
And its objective is to reveal even the most intimate secrets of the planet’s forests.
The GEDI mission, jointly developed by NASA’s Goddard Space Flight Center and the University of Maryland, enables unprecedented 3D mapping of forest areas right down to the sites most remote.
“It is a satellite the size of a refrigerator, it weighs about 500 kilos and is docked or connected to one of the modules of the International Space Station”, Spanish scientist Adrián Pascual, member of the GEDI scientific team, expert in mapping and management of forest ecosystems and professor at the University of Maryland, explained to BBC Mundo.
Mission data is essential to understand how much carbon forests store and what impact to deforestation in the fight against climate change.
But the future of GEDI is uncertain and currently a campaign seeks to ensure the continuity of the mission.
How GEDI works
GEDI is the English acronym for Global Ecosystem Dynamics Investigation or Research on the Global Dynamics of Ecosystems.
The heart of the program is an instrument that shoots laser beams and is linked to the International Space Station, ISS, from 600 .
“The ISS orbits the Earth non-stop. And our GEDI satellite is emitting laser pulses all the time”, said Pascual.
These energy pulses allow us to determine not only the height of the trees but also the structure of the forests.
“When that pulse of energy reaches the Earth it collides with the first element that finds, which is the top of the trees and continues to progress until it hits the ground”.
“The sensor measures the difference between when it detects the tops of the trees and the ground. And converting that time period into distance we are able to estimate the height of the vegetation“.
To reveal the composition of the forest, GEDI researchers study changes in the patterns of energy waves.
“We are thus able to estimate different levels of vegetation and that gives us an idea not only of the height of the forest, but also of its structural complexity”.
GEDI uses a remote sensing technology called LIDAR, which basically consists of pointing a laser at a surface and measuring the time it takes to return to its source.
It is not a new technology. “But this technology has never been put on a satellite and taken to the International Space Station and run over 193 km high to specifically monitor forests”, says Pascual.
Carbon: the key data
Trees capture CO2 or carbon dioxide from the atmosphere carbon, one of the main greenhouse gases responsible for climate change.
And they store a large part of that carbon, preventing it from being released into the atmosphere.
“When trees grow they increase their biomass. And approximately 10% of that biomass, of the wood of those trees, is carbon“, pointed out Pascual.
“It calculates more or less than an average size tree, the most general that can be thought, fixes some 25 kg of carbon dioxide per year”.
“We use GEDI then to know what is the stock, the carbon storage that currently exists in all the world’s forests”.
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The data and maps generated through from GEDI are publicly available.
And they are vital for governments around the world to realistically know what their cap is. carbon storage capacity.
“In the case of many ecosystems, it is not known how tall the trees are or what the forest is like,” explained Pascual.
“There are areas in the Amazon or in remote places, where we do not know how tall the trees are and what the distribution of biomass is like“.
GEDI makes it possible to detect and quantify changes in biomass resulting from forest fires or illegal logging.
The GEDI data also reinforces the importance of preserve the world’s mature forests, instead of prioritizing only new forest plantations.
Many countries include tree planting in their CO2 emission reduction plans.
“It is true that more trees must be planted as part of the solutions to combat climate change, through restoration projects on zon that are degraded and that have the potential to re-vegetate,” said Pascual.
However, “for many small trees to replace the carbon stored in a very large tree, many small trees are required, time, and that there are no phenomena in the middle such as a felling, a fire or an attack of pests”.
“No we can fall into the trap of thinking that we can replace large carbon stocks like in the Amazon, where there is a large amount of carbon stored, through plantations and restoration projects.”
El Furthermore, the carbon stored in forests is not only found on the ground.
“Under it, in the roots of the trees, the amount of carbon can be up to almost double what we are able to predict with GEDI. That is why it is vital to protect the ‘lungs’ of the Planet”.
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The campaign to save GEDI
Developing GEDI and understanding how its technology works from a space station took about 10 years of previous work. Numerous scientific studies were led by researchers such as Ralph Dubayah, GEDI principal investigator and professor at the University of Maryland.
The mission is scheduled to be operational only until the end of 2023, when GEDI would be replaced by another instrument on the International Space Station.
Both researchers and government representatives are currently supporting a campaign to extend GEDI’s life in space.
One of the scientists who is not part of the mission but uses its data is Flávia de Souza Mendes, a Brazilian scientist based in Germany and a member of the research group RSATE (Remote Sensing Applied to Tropical Environment
For Mendes, GEDI plays a crucial role in mitigating climate change.
“Climate change will affect more people and countries from unrepresented and low-income groups. Free GEDI data can make a difference in supporting policymaking and research in low-income countries.”
On the other hand, “the carbon market is very hot right now and many companies are emerging that calculate the carbon stored in the forest or in reforestation and afforestation projects to sell carbon credits”.
Adrián Pascual told BBC Mundo that “ there is a strong push from the international community to be able to keep GEDI longer. Because every week that it is up there we have thousands and thousands more observations that allow us to arrive at better estimates of the height of the vegetation and biomass”.
“It is a very big opportunity that we have to be able to maintain it for a few more months or years, because we really do not know when another possibility like this will exist again.”
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