Alejandra Martin’s BBC News World
Right now, a barrage of laser pulses is reaching Earth from the International Space Station.
And it aims to reveal the innermost secrets of the planet’s forests.
The GEDI mission, jointly developed by NASA’s Goddard Space Flight Center and the University of Maryland, provides unprecedented 3D maps of forested areas in even the most remote locations.
“It is a satellite the size of a refrigerator, weighing about 500 kilograms, which is anchored or attached to one of the modules of the International Space Station”, explains the Spanish scientist Adrián Pascual, member of the GEDI scientific team, expert to BBC Mundo in Forest Ecosystem Mapping and Management and Professor at the University of Maryland.
The mission’s data is crucial for understanding the amount of carbon stored in forests and the impact of deforestation on the fight against climate change.
However, the future of GEDI is uncertain and a campaign is currently underway to ensure the continuity of the mission.
GEDI is the abbreviation for Global Ecosystem Dynamics Investigation.
The core of the program is an instrument that fires laser beams and has been attached to the International Space Station (ISS) since 2019.
“The ISS orbits the Earth non-stop. And our GEDI satellite emits laser pulses all the time,” says Pascual.
These energy pulses make it possible to determine not only the height of the trees, but also the structure of the forests.
“When this energetic pulse reaches the Earth, it hits the first thing it encounters, which is the tree canopy, and continues to develop until it hits the ground.”
“The sensor measures the difference between when it detects treetops and the ground. And by converting that time to distance, we are able to estimate the height of the vegetation.”
To reveal the composition of the forest, GEDI researchers study changes in energy wave patterns.
“We are thus able to estimate the different levels of vegetation, which 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 involves pointing a laser at a surface and measuring the time it takes to return to the source.
It is not a new technology.
“But this technology has never before been put on a satellite and taken to the International Space Station to operate at an altitude of over 400 km to specifically monitor forests,” says Pascual.
Carbon: key data
Trees capture CO2 or carbon dioxide, one of the main greenhouse gases responsible for climate change, from the atmosphere.
And they store much of that carbon, preventing it from being released into the atmosphere.
“When trees grow, they increase their biomass. And about 50% of that biomass, the wood in those trees, is carbon,” says Pascual.
“It is roughly estimated that an average-sized tree, as generally as you can imagine, fixes around 25 kg of carbon dioxide per year.
“So we are using the GEDI initiative to determine what is stored, the storage of carbon that currently exists in all forests in the world”.
GEDI’s role in the fight against climate change
Data and maps generated by GEDI are publicly available.
And they are essential for governments around the world to realistically know what their carbon storage capacity is.
“In the case of many ecosystems, we don’t know how tall the trees are or what the forest looks like,” says Pascual.
“There are areas in the Amazon or remote places where we don’t know how tall the trees are and what the biomass distribution is.”
GEDI makes it possible to detect and quantify changes in biomass as a result of forest fires or illegal felling.
The GEDI data also reinforces the importance of conserving the world’s mature forests rather than prioritizing new forest plantations.
Many countries include tree planting in their plans to reduce CO2 emissions.
“It is true that more trees must be planted as part of the solutions to combat climate change through restoration projects in degraded areas that have the potential to be rebuilt,” Pascual points out.
But “for many small trees to replace the carbon stored in a very large tree takes many small trees, time, and the absence of intervening events such as logging, fires, or pest attacks. .
“We cannot fall into the trap of thinking that we can replace large carbon stores like the Amazon, where there is a large amount of stored carbon, with plantations and restoration projects.”
The carbon stored in forests is not only on the surface.
“Underground, in the roots of the trees, the amount of carbon can be up to almost double what we are able to predict with GEDI. Therefore, it is important to protect the ‘lungs’ of the planet.”
The campaign to save GEDI
Developing GEDI and understanding how its technology works from a space station took nearly 20 years of preliminary work.
Many scientific studies have been conducted by researchers such as Ralph Dubayah, GEDI’s principal investigator and professor at the University of Maryland.
The mission is expected to be operational only until the end of 2023, when GEDI will be replaced by another instrument aboard the International Space Station.
Scientists and officials are currently supporting a campaign to extend GEDI’s life in space.
One of the researchers 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 RSATE (Remote Sensing Applied to Tropical Environment) research group.
For Mendes, GEDI plays a crucial role in mitigating climate change.
“Climate change will affect more people and countries from underrepresented and low-income groups. Free GEDI data can make a difference to support policy-making and research in low-income countries.”
On the other hand, “the carbon market is very active at the moment and many companies are emerging to calculate the carbon stock in the forest or in replanting and afforestation projects to sell carbon credits”.
Adrian Pascual told BBC Mundo that “there is a strong pressure from the international community to be able to keep GEDI for longer. In fact, every week he is here, we have thousands and thousands more observations. which gives allow us to obtain better estimates of vegetation height and biomass”.
“It’s a fantastic opportunity for us to be able to keep it going for a few more months or years, because we really don’t know when another opportunity like this will come along.