Alejandra Martins BBC News World
Right now, a shower of laser pulses from the International Space Station is reaching Earth.
And it aims to reveal the secrets underlying 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 kilos and which is docked or attached to a module of the International Space Station”, explained to BBC Mundo the Spanish scientist Adrián Pascual, member of the GEDI scientific team, specialized in the mapping and management of forest ecosystems and University of Maryland Professor Dr.
Mission data is essential to understanding the amount of carbon stored by forests and the impact of deforestation in combating climate change.
But GEDI’s future is uncertain and a campaign is currently underway to ensure the continuation of the mission.
GEDI is an acronym 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 Earth nonstop. And our GEDI satellite emits laser pulses all the time,” Pascual said.
These energy pulses make it possible to determine not only the height of the trees, but also the structure of the forest.
“When this powerful pulse reaches Earth, the first thing it encounters is the tree canopy, and it continues to progress until it reaches the ground.”
“By measuring the difference between when the sensor detects the top of the tree and the ground. And by converting that time to distance, we’re able to estimate the height of the tree.”
To reveal forest structure, GEDI researchers study changes in energy wave patterns.
“In this way we were able to estimate 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 its source.
This 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 altitudes above 400 km specifically for forest monitoring,” said Pascual.
Carbon: Basic Facts
Trees capture 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, they increase their biomass. And about 50% of that biomass, the wood of that tree, is carbon,” Pascual said.
“It is roughly estimated that an average-sized tree, as can be generally imagined, fixes about 25 kg of carbon dioxide per year.
“So we’re using the GEDI initiative to determine what is the stock, the storage of carbon that currently exists in all the world’s forests.”
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 many ecosystems, we don’t know how tall the trees are or what the forest looks like,” Pascual said.
“There are areas in the Amazon or in remote areas where we don’t know how tall the trees are and what the distribution of biomass is.”
GEDI makes it possible to detect and quantify changes in biomass caused by forest fires or illegal logging.
GEDI data reinforces the importance of conserving the world’s mature forests rather than prioritizing new forest planting.
Many countries include tree planting in their plans to reduce CO2 emissions.
“It is true that more trees need to be planted as part of the solution to combating climate change, through restoration projects in degraded areas that have the potential to regenerate,” Pascual noted.
However, “replacing the carbon stored in one very large tree for many small trees takes many small trees, time, and the absence of intermediate events such as logging, fire, or insect attack.
“We can’t fall into the trap of thinking that we can replace large carbon stocks like the Amazon, which have a lot of stored carbon, with afforestation and restoration projects.”
Carbon stored in forests is not just at the surface.
“Underground, in the roots of trees, the amount of carbon can be almost twice what we can predict with GEDI. So protecting the ‘lungs’ is important. For the planet.”
Campaign to save GEDI
It took nearly 20 years of preliminary work to develop GEDI and understand how its technology works from a space station.
Many scientific studies have been conducted by researchers such as Ralph Dubaya, GEDI principal investigator and professor at the University of Maryland.
The mission is expected to be operational only by the end of 2023, when GEDI will be replaced by another instrument aboard the International Space Station.
Researchers and government officials are currently supporting a campaign to extend GEDI’s life in space
One of the scientists who is not part of the mission but is using its data is Flavia 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 an important role in climate change mitigation.
“Climate change will affect more people and countries from underrepresented 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 active at the moment and many companies are starting to calculate carbon stored in forests or in reforestation and reforestation projects to sell carbon credits”.
Adrian Pascual told BBC Mundo that “there is strong pressure from the international community to be able to hold GEDI longer. In fact, every week he is here we have thousands more sightings. That allows us to get better estimates of vegetation height and biomass.” “.
“It’s a great opportunity for us to be able to hold on to it for a few more months or years, because we really don’t know when there will be another opportunity like this.