Nitrogen Boosts Tropical Forest Growth & Carbon Capture, Study Finds

Tropical forests recovering from deforestation could significantly boost their carbon capture potential with a simple boost: nitrogen. A new study published on January 13, 2026, in Nature Communications, reveals that adding nitrogen to the soil of regenerating forests can nearly double their growth rate, offering a promising new avenue for climate change mitigation.

Researchers discovered that nitrogen availability is a key limiting factor in the early stages of tropical forest regrowth. When nitrogen fertilizer was applied to recently cleared land – areas that had been cattle pastures for less than a year – tree biomass increased by 95% compared to control groups that did not receive the fertilizer. Even ten-year-old recovering forests showed a substantial 48% increase in growth with the nitrogen treatment.

“We all rely on tropical forests to stabilize our climate,” explains Sarah Batterman, an associate professor at the University of Leeds and study co-author. “They store about half of forest carbon and sequester about 20% of our carbon emissions. But there’s huge uncertainty in whether tropical forests will continue to take up CO₂ or will become a source of carbon into the atmosphere in the future. One of the key uncertainties is the role of nutrients in supporting more carbon sequestration and recovery from disturbance.”

The study, conducted within the Panama Canal Watershed in lowland tropical forest, involved a large-scale experiment where researchers tracked the growth of trees and woody vines over a four-year period. They tested the impact of nitrogen, phosphorus, or a combination of both on forest regeneration across different stages of recovery – from recently cleared pastures to 600-year-old forests. Field teams regularly fertilized the trees for three months each year, carefully measuring trunk diameters to extrapolate aboveground biomass and carbon storage.

Interestingly, the research found that phosphorus did not limit forest growth at any stage of maturity. The most significant impact came from addressing nitrogen deficiency, a common consequence of deforestation. When forests are cleared, essential nitrogen can evaporate or wash away from the disturbed soil, hindering the regrowth process. This depletion can persist for decades, even after reforestation efforts are underway.

Jefferson Hall, director of the Agua Salud project at the Smithsonian Tropical Research Institute (STRI), emphasizes that the findings don’t necessarily call for widespread fertilization of tropical forests. Instead, the research highlights the importance of prioritizing nitrogen-fixing tree species in reforestation projects. These trees have a natural ability to convert atmospheric nitrogen into a usable form, enriching the soil and accelerating carbon sequestration.

“It’s not practical that people are going to go out and, you know, fertilize all the forests of the world to capture CO₂,” Hall stated. “The natural way of enhancing the nitrogen system would be to plant more nitrogen-fixing trees.”

The findings corroborate long-held observations about nutrient limitations in tropical forests. Richard Birdsey, a senior scientist at the Woodwell Climate Research Center, who was not involved in the study, noted that the issue of nutrient depletion has been recognized for decades. However, this study provides robust experimental evidence to support those observations.

Recovering tropical forests play a crucial role as a global carbon sink, absorbing approximately 2.5 pentagrams of carbon annually. Globally, forests absorb around 3.5 pentagrams, making tropical forests the largest component of the overall carbon sink, with regenerating forests contributing significantly to this absorption.

The study authors highlight the importance of understanding these nutrient dynamics to accurately predict how quickly regenerating forests will accumulate carbon and contribute to climate change mitigation. By focusing on nitrogen availability, conservationists can potentially enhance reforestation efforts and accelerate the pace of carbon capture in these vital ecosystems.

Tang, W., Hall, J. S., Phillips, O. L., Brienen, R. J. W., Wright, S. J., Wong, M. Y., Hedin, L. O., Van Breugel, M., Yavitt, J. B., Hannam, P. M., & Batterman, S. A. (2026). Tropical forest carbon sequestration accelerated by nitrogen. Nature Communications, 17(1), 55. https://doi.org/10.1038/s41467-025-66825-2