Tropical forests regrow twice as fast with nitrogen-rich soil

A 20-year experiment across Central America has revealed something straightforward but powerful: when soil has enough nitrogen, recovering tropical forests grow roughly twice as fast. That matters because every year of faster regrowth means more carbon pulled from the atmosphere and locked into wood and roots.

The research, published today in Nature Communications, tracked 76 forest plots spread across Central America—each about a third of a football pitch—at different stages of recovery from logging, farming, and other clearing. Scientists from the University of Leeds, Yale, Princeton, and other institutions tested what happened when they added nitrogen, phosphorus, or both to some plots while leaving others untreated.

The results were unambiguous. During the first decade of regrowth, forests with adequate nitrogen rebounded about twice as quickly as nitrogen-poor sites. Phosphorus alone didn't produce the same effect. The difference compounds over time: a forest that grows faster in its early years captures significantly more carbon before it reaches maturity.

What This Means for Climate and Reforestation

Tropical forests are among Earth's most efficient carbon sinks. They pull CO₂ from the atmosphere and store it in wood and soil. If nitrogen limitations are holding back young tropical forests worldwide—which the researchers suspect they are—the planet could be missing out on roughly 0.69 billion tonnes of stored carbon dioxide annually. For context, that's about two years' worth of the UK's total greenhouse gas emissions.

Lead researcher Wenguang Tang, who conducted this work during his PhD at Leeds, put it plainly: "Our study suggests there are ways we can boost greenhouse gas capture through reforestation by managing the nutrients available to trees."

But here's the catch: you can't just spray nitrogen fertilizer across recovering forests at scale. That would trigger harmful side effects, including increased emissions of nitrous oxide, a potent greenhouse gas itself. Instead, the team points to practical alternatives. Forest managers could plant trees from the legume (bean) family, which naturally enrich soils with nitrogen. Another option is restoring forests in areas that already have sufficient nitrogen from air pollution—a rare case where pollution creates an opportunity.

The timing of this research aligns with real-world momentum. The study arrives shortly after COP 30 in Brazil announced the Tropical Forest Forever Facility, a fund designed to help tropical countries protect and restore forests. Dr. Sarah Batterman, the study's principal investigator, noted that these findings have direct implications for where and how policymakers should prioritize forest restoration to maximize carbon sequestration.

The research doesn't suggest we should stop protecting mature tropical forests—avoiding deforestation remains the priority. But for the vast areas already cleared and beginning to recover, understanding what accelerates that regrowth gives us a clearer path to turning degraded land back into a climate solution.