Scientists have found that nitrogen in the soil plays a major role in helping tropical forests grow back faster after deforestation. This discovery could change how countries plan forest recovery and climate solutions in the future. The research was led by the University of Leeds and involved scientists from many well-known institutions around the world. These included the Smithsonian Tropical Research Institute in Panama, Yale University, Princeton University, Cornell University, the University of Glasgow, and the National University of Singapore.
The findings were published in the journal Nature Communications and are based on the longest and largest experiment ever carried out on forest regrowth and soil nutrients. Tropical forests are often cut down for farming, logging, or grazing. When the cutting happens, the land does not always recover on its own. Some forests grow back slowly, while others struggle to return at all. The researchers wanted to understand why such an event happens and whether soil nutrients could make a difference.
To study this, scientists selected 76 forest plots across Central America. Each plot was about one-third the size of a football field. The forests were of different ages, from recently cleared land to areas that had been regrowing for many years. Researchers tracked how trees grew and died over a period of up to 20 years. The plots were divided into four groups. A group received nitrogen fertiliser. Another received phosphorus fertilizer. A third group received both nutrients. The last group received no fertiliser at all. This method allowed scientists to compare how forests responded under different soil conditions. The results were very clear. In young forests, nitrogen made a huge difference.
During the first ten years of regrowth, trees with enough nitrogen grew nearly twice as fast as trees that lacked it. The amount of plant material above the ground increased sharply when nitrogen was available. However, the effect changed as forests aged. Older forests did not seem to benefit much from extra nitrogen or phosphorus. This study shows that young forests are strongly limited by nitrogen, but mature forests are not. Phosphorus, on the other hand, did not appear to limit growth at any stage of forest recovery.
Nitrogen is essential for plants. It helps trees build leaves, stems, and branches. Too much nitrogen can be harmful. When it builds up in the soil, it can cause eutrophication. This means the soil gets overloaded with nutrients. Extra nitrogen can also wash into rivers and lakes. This pollutes the water and hurts wildlife. Because of these risks, researchers warn against spreading fertiliser directly on forests. It is not a safe long-term solution.Fertiliser production also uses a lot of energy and releases nitrous oxide, a powerful greenhouse gas. For these reasons, large-scale fertilising may not be practical or safe. Instead, scientists suggest more natural solutions. One option is planting trees that naturally add nitrogen to the soil. These include legume species. They work with bacteria to pull nitrogen from the air. Then they store it in the ground.
Another approach is to focus reforestation on land with higher nitrogen or richer soils. The study shows a key link between soil nutrients and climate change. Tropical forests are very important carbon sinks. They absorb carbon dioxide from the air. They store it in plants and soil.
When forests grow slowly, they capture less carbon. Researchers estimate that nitrogen shortages may stop tropical forests from absorbing hundreds of millions of tonnes of carbon dioxide each year. Over decades, this lost carbon storage could match years of emissions from an industrialised country like the United Kingdom. Healthy soil is essential for healthy forests. Nutrients like nitrogen play a key role in forest regrowth. Governments and conservation groups can use this knowledge to plan better reforestation programs. These strategies can help forests recover faster. They can also store more carbon. This boosts their role in fighting climate change.
