Smithsonian And NASA Collaborate To Understand Tropical Forests On Different Continents

The effects of climate on forest biomass differs among forests on with different histories on a continental scale

Satellite images can be used to estimate how much carbon forests store as aboveground biomass (AGB) and how biomass varies in different forests. In a study published in the journal Nature, a team of researchers affiliated with the Smithsonian Tropical Research Institute (STRI), the University of Maryland, NASA, and the Universidade Federal dos Vales do Jequitinhonha e Mucuri, Brazil analyzed 16 million 2020 NASA-GEDI satellite estimates of biomass from forests in the Amazon, the Congo Basin and Southeast Asia and discovered that the effects of temperature, aridity, soil nutrients and other environmental variables on forest biomass differ from place to place.

“This study definitively shows that tropical forests on different continents respond differently to climate,” said Helene Muller-Landau, a co-author of the study and a staff scientist at STRI in Panama. “This is consistent with the idea that the very different historical climates and evolutionary trajectories in Africa, Asia, and the Americas have enduring legacies in how forest biomass varies with climate.”

“Our GEDI spaceborne LIDAR mission, which uses laser pulses to measure the three-dimensional structure of forests, made it possible to connect aboveground forest biomass measurements with climate, soils and topography,” said lead author Matheus Nunes, Assistant Research Professor in the Department of Geographical Sciences at the University of Maryland, College Park and a scientist with NASA’s Global Ecosystem Dynamics Investigation (GEDI) mission.

Not all tropical forests are the dense jungles people may imagine them to be. Tropical trees with lightweight wood, like balsa, store much less carbon than dense hardwood trees like rosewood or ebony. Some forests contain towering tropical giants, and others contain much smaller trees. The type of forest in an area also depends on the soil and whether the terrain is flat or mountainous, dry or swampy. This study shows that among site variation in climate had different impacts on forest biomass in different areas, depending on the continent and on the values of other environmental variables.

“The study underscores the major role that events over a geological time scale, including landscape and climate changes, have shaped the extant tropical rainforest,” said Carlos Jaramillo, paleobiologist and staff scientist at STRI.

“It is not enough to have global analyses that show how the environment, including climate, affects the structure of vegetation, as these effects are very heterogeneous and depend strongly on the local context,” adds Nunes. “Therefore, we need local analysis and local experts who know the landscape well to make better predictions of the effects of climate on tropical forests.”

In general sites with higher temperatures tended to have lower biomass, but with marked differences among regions.  Forests in Africa’s Congo Basin were particularly sensitive to temperature, whereas Amazonian forests were moderately sensitive and Southeast Asian forests were relatively insensitive.  In contrast, water limitation was most important in Southeast Asia where biomass decreased strongly in more arid sites, while Amazonian forests showed peak biomass at intermediate aridity, and African forests were relatively insensitive to aridity. 

Across regions, the effects of different climate variables were further modified by soils and landscape features. In the tallest forests, where trees grow to more than 70 meters (about 230 feet) tall, storms—lightning and windthrow—may be the most important factors that reduce forest biomass.

These results help to resolve debates ignited by conflicting findings on forest biomass patterns in previous studies, showing that this variation, in part, reflects real biological variation, not methodological differences.

“Africa has a drier history, Southeast Asia has wetter history, and these histories have shaped what species are there, and how they respond to climate.  So the fact that the forests look different in fascinating ways between Africa, America, and Asia is not just a curiosity – it’s fundamental to understanding the forests,” said Muller-Landau. “New networks of forest plots, such as the GEO-TREES network, which use the same methods to measure forest carbon at different sites, will be important as we continue to verify satellite carbon estimates in the future.”

Reference: Nunes, M.H., Muller-Landau, H.C., Görgens, E.B., Pascual, A., and Dubaya2026. Heterogeneous climatic controls on tropical-forest biomass, Nature, DOI https://doi.org/10.1038/s41586-026-10880-2

About the Smithsonian Tropical Research Institute

Headquartered in Panama City, Panama, STRI is a unit of the Smithsonian Institution. Our mission is to understand tropical biodiversity and its importance to human welfare, to train students to conduct research in the tropics and to promote conservation by increasing public awareness of the beauty and importance of tropical ecosystems. Watch our video, and visit our website, Facebook and Instagram for updates.

Elisabeth King | Read More

As Communications Manager at the Smithsonian Tropical Research Institute (STRI) in Panama, Elisabeth King bridges the gap between research scientists and diverse audiences. She writes about science, creates exhibitions and video scripts in English and Spanish, making STRI research available to all audiences from school kids to ambassadors.