Scientists led by the University of Leeds launched the largest and longest experiment ever designed to examine how nutrients shape forest regrowth. The work focused on tropical areas previously cleared for activities such as logging and agriculture.

Tracking Forest Regrowth Over Decades

The researchers selected 76 forest plots across Central America and monitored them for as long as 20 years. Each site differed in age and size, allowing the team to follow how trees grew and died as forests recovered over time.

To test the role of nutrients, the plots received different treatments. Some were given nitrogen fertilizer, others phosphorus fertilizer, some received both nutrients, and some were left untreated. This approach allowed the scientists to directly compare how forests responded under different soil conditions.

Nitrogen Emerges as a Key Driver

The results showed that soil nutrients strongly influence how quickly tropical forests regrow. During the first 10 years of recovery, forests with adequate nitrogen rebounded at about twice the rate of those lacking it. Phosphorus alone did not produce the same effect.

The study included researchers from the University of Glasgow, the Smithsonian Tropical Research Institute, Yale University, Princeton University, Cornell University, the National University of Singapore, and the Cary Institute of Ecosystem Studies. The findings were published on January 13 in the journal Nature Communications.

Implications for Climate and Reforestation

Lead author Wenguang Tang, who carried out the research while completing his PHD at the University of Leeds, said: "Our study is exciting because it suggests there are ways we can boost the capture and storage of greenhouse gases through reforestation by managing the nutrients available to trees."

Although nitrogen fertilizer was used in the experiment, the researchers do not recommend fertilizing forests. Widespread fertilizer use could lead to harmful side effects, including emissions of nitrous oxide, a powerful greenhouse gas.

Instead, the team suggests practical alternatives. Forest managers could plant trees from the legume (bean) family, which naturally add nitrogen to the soil. Another option is restoring forests in areas that already have sufficient nitrogen due to the effects of air pollution.

Why Faster Regrowth Matters for the Climate

Tropical forests are among the world's most important carbon sinks. They help slow climate change by removing carbon from the atmosphere and storing it in trees, a process known as carbon sequestration.

The researchers estimate that if nitrogen shortages affect young tropical forests worldwide, about 0.69 billion tonnes of carbon dioxide may be failing to be stored each year. That amount is roughly equal to two years of carbon dioxide and other greenhouse gas emissions in the U.K.

Policy Relevance After COP 30

The study is released just weeks after the close of COP 30 in Brazil, where the Tropical Forest Forever Facility (TFFF) fund was announced. The initiative aims to help tropical forest countries protect existing forests and restore those that have been damaged.

Principal investigator Dr. Sarah Batterman, an Associate Professor in Leeds' School of Geography, said: "Our experimental findings have implications for how we understand and manage tropical forests for natural climate solutions.

"Avoiding deforestation of mature tropical forests should always be prioritized, but our findings about nutrient impacts on carbon sequestration is important as policymakers evaluate where and how to restore forests to maximize carbon sequestration."