The Hidden Pollutant Altering Forest Respiration

For centuries, forests have operated according to a predictable biological rhythm. Beneath the tree canopy, a complex network of roots and microscopic organisms functions tirelessly. These organisms break down dead leaves, wood, and other organic material. As they digest this matter, they release carbon dioxide into the air. This process simultaneously fuels the growth of new plants.

Scientists call this continuous release of gas "soil respiration." It represents one of the largest movements of carbon on Earth. Carbon travels from the soil into the atmosphere through this natural breathing process. It is a critical component of the global carbon cycle.

However, new research indicates that this ancient rhythm is being disrupted. The cause is a growing, yet often overlooked, form of pollution: excess nitrogen. This chemical imbalance alters how forests exchange gases with the atmosphere. It changes the fundamental health of woodlands around the world.

A forest floor may appear calm on a cool spring morning. Beneath the surface, however, billions of microbes are busy at work. They decompose fallen leaves and rotting wood. At the same time, tiny tree roots release carbon dioxide as they grow. Together, these activities create a steady exchange of carbon between the land and the sky.

For decades, forests have been exposed to rising levels of nitrogen pollution. Human activities such as burning fossil fuels, manufacturing, and farming release reactive nitrogen into the air. This pollution originates from vehicle exhaust, industrial smokestacks, and fertilizers spread on crops. Eventually, this nitrogen returns to the ground. It falls as rain, snow, or settles as airborne particles.