Amazon rainforest from above

Nasa space laser used to measure rainforest canopies

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Satellite data has shown that the structure of tropical forests is simpler and more exposed to sunlight than previously thought.

An international research team has used the data collected by Nasa’s Global Ecosystem Dynamics Investigation (GEDI) to improve current understandings of rainforest canopies - the place where the majority of the world’s species live.

Launched in 2018, the space laser has provided the first detailed structure of the global rainforests.

"Most of the world's species live in tropical forests and most of those make use of the canopy, and yet, we know so little," said Christopher Doughty, professor at the University of Northern Arizona. "Rainforest structure matters because it controls how animals access resources and escape predators, and these findings will help us understand tropical forest animal's susceptibility to climate change."

Traditionally, rainforest researchers have divided them into three vertical layers, which host different types of flora and fauna. Nonetheless, this was only true of specific locations, with the structure of the majority of the world’s rainforests remaining relatively unknown - until now. 

Using GEDI, scientists have been able to prove that the structure of tropical forests is simpler and more exposed to sunlight than previously thought.

The satellite is capable of shooting a laser from the International Space Station (ISS) onto the Earth thousands of times a day. It measures the time it takes to return and the level of energy that the satellite receives, and uses the data to create a 3D-map of the Earth’s biomass.

The data provided by GEDI could be key for scientists’ understanding of the global biomass, its change over time and the effects of global warming. 

"A key difference between GEDI and many other satellites is its measurement of three-dimensional canopy structure," said Hao Tang, professor at the National University of Singapore (NUS) and co-author on the paper. 

"Conventional satellites, while providing valuable data on land cover and canopy greenness, often lack the detailed vertical information offered by GEDI. This vertical information is crucial for understanding ecosystem dynamics, carbon storage and biodiversity that cannot be easily seen from typical satellite images.”

Analysis of the data provided by GETI has already been used to make important advances in our understanding of rainforests. 

Using these 3D-maps, the research team was able to conclude that the majority of tropical forests - accounting for 80 per cent of the Amazon and 70 per cent of Southeast Asia and the Congo Basin - have a peak in the number of leaves at 15 metres instead of at the canopy top, as previously thought. 

As a result, the scientists concluded that  deviation from more ideal conditions (like lower fertility or higher temperatures) leads to shorter, less stratified forests with lower biomass.

"It was really surprising to see the dominance of this structure type because it differs from what we had learned in the classic textbooks on the topic," Doughty said. "These findings will not only help us understand how the millions of species that live in a rainforest canopy might acclimate to changing temperatures, but also how much carbon these forests hold and how good they are at fighting climate change."

The researchers’ findings were published in the journal Environmental Research Ecology.

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