- Alejandra Martins
- BBC News World
7 hours ago
Credit, NASA, Goddard Space Flight Center
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GEDI fires pulses of energy at the Earth’s surface 242 times per second
Right now, a shower of laser pulses is coming down to Earth from the International Space Station (ISS).
And their goal is to unveil even the most intimate secrets of the planet’s forests.
The GEDI mission, jointly developed by NASA’s Goddard Space Flight Center (US space agency) and the University of Maryland, USA, enables unprecedented 3D mapping of forested areas even in the most remote locations.
“It’s a satellite the size of a fridge, it weighs about 500 kilograms and it’s docked or linked to one of the International Space Station’s modules,” Spanish scientist Adrián Pascual told BBC News Mundo, the BBC’s Spanishlanguage news service , member of the GEDI science team, specialist in mapping and management of forest ecosystems and professor at the University of Maryland.
Mission data is critical to understanding how much carbon forests store and the impact of deforestation in the fight against climate change.
But GEDI’s future is uncertain and a campaign is currently trying to ensure the continuity of the mission.
How does GED work?
GEDI is the abbreviation for Global Ecosystem Dynamics Investigation.
And at the heart of the program is an instrument that shoots laser beams and has been docked with the International Space Station since 2019.
Credit, NASA, Goddard Space Flight Center
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The rain of laser pulses can be used not only to determine the height of trees, but also the structure of forests.
“The ISS orbits the Earth continuously. And our GEDI satellite continuously emits laser pulses,” explains Pascual.
With these energy impulses, not only the height of trees, but also the structure of forests can be determined.
“When this pulse of energy reaches the earth, it hits the first element it hits, which is the treetops, and continues to travel until it hits the ground.”
“The sensor measures the difference between the moment the treetops and the ground are detected. And by converting that time interval into a distance, we can estimate the height of the vegetation.”
To uncover the composition of the forest, GEDI researchers are studying changes in energy wave patterns.
“In this way, we can estimate different degrees of vegetation and thus not only get an idea of the height of the forest, but also of its structural complexity.”
Credit, Kindness Adrián Pascual
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“Studying forests all over the world with the same instrument and generating trillions of observations is something really unique,” says Adrián Pascual
GEDI uses a distance detection technology called LIDAR, which basically consists of aiming a laser at a surface and measuring the time it takes to return to its source.
However, it is not a new technology.
“But this technology has never been put on a satellite and taken to the International Space Station and used at more than 400 km altitude to specifically monitor forests,” explains Pascual.
Credit, Getty Images
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About 50% of the biomass in the wood of trees is carbon
Carbon: the fundamental data
Trees absorb CO2 or carbon dioxide from the atmosphere, one of the main greenhouse gases responsible for climate change.
And they store much of that carbon, preventing it from being released into the atmosphere.
“As trees grow, their biomass increases. And about 50% of that biomass, the wood of those trees, is carbon,” says Pascual.
“It is estimated that a mediumsized tree, the most common one imaginable, captures about 25 kg of carbon dioxide per year.”
“We use GEDI to know what is the stock of carbon currently present in all the world’s forests.”
The role of GEDI in the fight against climate change
The data and maps generated from GEDI are publicly available.
And they are critical for governments around the world to realistically know what their carbon storage capacity is.
Credit, Kindness Adrián Pascual
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GEDI Data Visualization Colors represent tonnes of air biomass per hectare on the top map, while the bottom map shows the GEDI biomass model’s prediction error
“In many ecosystems, you don’t know how tall the trees are or what the forest is like,” says Pascual.
“There are regions in the Amazon and in remote places where we don’t know how tall the trees are and how the biomass is distributed.”
GEDI makes it possible to detect and quantify changes in biomass caused by forest fires or illegal logging.
The GEDI data also underscores the importance of preserving the world’s mature forests, rather than just prioritizing new forest plantations.
Many countries include tree planting in their plans to reduce carbon emissions.
“It is true that there is a need to plant more trees as part of the solutions to combating climate change, through projects to restore degraded areas with the potential to have vegetation again,” says Pascual.
“But for many small trees to replace the carbon that a very large tree has stored, it takes time for many small trees, and in the meantime there are no phenomena such as felling, fire or pest infestation.”
“We cannot fall into the trap of thinking that we can replace large carbon stocks like in the Amazon, where there is a large amount of stored carbon, with plantations and restoration projects.”
In addition, the carbon stored in forests is not only found above ground.
“Below, in the roots of the trees, the amount of carbon could be almost double what we can predict with GEDI. That’s why it’s important to protect the planet’s ‘lungs’.”
Credit, Getty Images
The campaign to save the GEDI
Developing GEDI and understanding how its technology works from a space station took nearly 20 years of groundwork. Numerous scientific studies have been conducted by researchers such as Ralph Dubayah, principal investigator of GEDI and professor at the University of Maryland.
The mission is only scheduled to operate until the end of 2023, when GEDI will be replaced by another instrument on the International Space Station.
Both researchers and government officials are currently supporting a campaign to extend the lifespan of GEDI in space.
Credit, NASA, Goddard Space Flight Center
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GEDI has been docked with the International Space Station since 2019
One of the scientists not part of the mission but using their data is Flávia de Souza Mendes, a Germanybased Brazilian scientist who is part of the RSATE (Remote Sensing Applied to the Tropical Environment) research group.
For Mendes, GEDI plays a crucial role in climate protection.
“Climate change will affect more people and countries from underrepresented and lowincome groups. Free GEDI data can make a difference in supporting policymaking and research in lowincome countries.”
On the other hand, “the CO2 market is currently very heated and many companies are emerging that calculate the CO2 stored in the forest or in reforestation and forestry projects in order to sell CO2 certificates”.
Adrián Pascual told BBC News Mundo that “there is strong pressure from the international community to be able to maintain GEDI for longer”.
“Because it’s up there every week, we have thousands and thousands of observations that allow us to make better estimates of vegetation height and biomass.”
“There’s a huge chance we’ll have to keep him for a few more months or years because we really don’t know when we’re going to have another opportunity like this.”
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