NASA’s Space Laser Provides Answers to Mystery of the Rainforest Canopy – NAU Review
We know less about the rainforest canopy, where most of the world’s species live, than we do about the surface of Mars or the ocean floor. However, that is about to change thanks to GEDI – a NASA space laser that has rendered a detailed structure of the world’s rainforests for the first time ever.
“Tropical forests are mainly unordered in the Amazon and areas with low fertility or high temperatures,” reads the title of the paper recently published in Environmental Research Ecology detailing the laser findings. Written by researchers from the US, UK and Singapore, Christopher Dotya professor in NAU’s School of Informatics, Computing, and Electronic Systems and first author of the study, believes this research is important—and long overdue—in discovering more about tropical ecosystems.
“Most species in the world live in tropical forests and most make use of the canopy, however, so little we know,” Doughty said. “Rainforest structure is important because it controls how animals access resources and predators escape, and these findings will help us understand the vulnerability of tropical forest animals to climate change.”
Research into forest canopies has come a long way. Early Western visitors described tropical forests as empty horror (nature hates a void) because vegetation was “eager to fill every available space with stems and leaves.” Later, when scientists began to study tropical forests, they classified leafy plants into forest layers—a thick upper crown and a thick middle layer with a thin layer in between. However, this has only been observed in a few well-studied sites. The structure across most of the tropical forest was still unknown.
Then came GEDI, an investigation into the dynamics of the global ecosystem.
“The main difference between GEDI and many other satellites is their measurement of the three-dimensional structure of the parachute,” said Hau Tang, a professor in the Department of Geography at the National University of Singapore (NUS) and a co-author on the paper. Tang, also a Principal Investigator at the NUS Center for Nature-Based Climate Solutions, added, “Traditional satellites, while providing valuable data on land cover and canopy greenness, often lack the detailed vertical information provided by GEDI. Such vertical information is essential to understanding ecosystem dynamics and carbon storage and biodiversity that are not easily seen from typical satellite images.”
NASA’s GEDI, launched in late 2018, shoots invisible lasers from the International Space Station into Earth’s forests thousands of times a day. Depending on how much energy is returned to the satellite, it can provide a detailed 3D map showing where leaves and twigs are in the forest and how they change over time. This will help researchers understand the amounts of biomass and carbon forests store and how much they lose when disturbed—information vital to understanding Earth’s carbon cycle and how it is changing.
Doty, Tang, and the paper’s other authors analyzed GEDI data across all tropical forests and found that the structure was simpler and more exposed to sunlight than previously thought. The data also revealed that most tropical forests (80 percent of the Amazon and 70 percent of Southeast Asia and the Congo Basin) have a peak in leaf number at 15 meters rather than the top of the canopy, completely debunking the in-highest theory of the early researchers. . While forests varied, the main finding that seemed consistent in each scenario was that deviation from more ideal conditions (such as lower fertility or higher temperatures) leads to shorter, less stratified forests with lower biomass.
“It was really surprising to see the predominance of this kind of structure because it’s so different from what we’ve been taught in classic textbooks on the subject,” Doughty said. “Not only will these findings help us understand how the millions of species that live in the rainforest canopy can adapt to changing temperatures, but also how much carbon these forests contain and how well they are at combating climate change.”