Soil nitrogen doubles tropical forest regrowth in early recovery.

A long-term experiment across 76 Central American plots found that adequate soil nitrogen can double tropical forest regrowth during the first decade of recovery; the study was published January 13 in Nature Communications.

Researchers report that what happens in soil matters for how fast tropical forests return after land is cleared. The team ran the largest and longest nutrient experiment aimed at forest regrowth. They monitored 76 plots in Central America for up to 20 years and compared plots that received nitrogen, phosphorus, both nutrients, or no additions. The work was published on January 13 in Nature Communications and involved several institutions, including the University of Leeds, the Smithsonian Tropical Research Institute, and multiple universities. Key findings: - The experimental results showed that plots with adequate nitrogen rebounded at about twice the rate of those lacking nitrogen during the first 10 years of recovery. - Phosphorus additions alone did not produce a similar increase in early regrowth. - The experiment used direct nutrient treatments (nitrogen, phosphorus, both, or none) across sites that varied in age and size and were monitored for up to two decades. - The authors caution that applying nitrogen fertilizer broadly is not recommended because it can produce harmful side effects such as nitrous oxide emissions. - As alternatives, the research notes planting nitrogen-fixing species (for example, legumes) and restoring areas that already have higher soil nitrogen as possible approaches mentioned by the authors. - The team estimates that nitrogen shortages in young tropical forests could be associated with about 0.69 billion tonnes of CO2 not being stored each year; the study was released shortly after COP 30, where the Tropical Forest Forever Facility was announced. Summary: The study indicates that soil nitrogen availability strongly influences early tropical forest regrowth and therefore affects carbon storage in recovering forests. The authors say the findings have implications for natural climate solutions and for how restoration is understood, while also emphasizing that avoiding deforestation of mature forests remains a priority. Some policy discussions are underway following COP 30, but specific policy responses are undetermined at this time.