Nitrogen is an essential part of our ecosystem. The nitrogen-based compounds must cycle through air, water, and soil in a delicate balance to make the ecosystem function.

Human activity disrupts the natural balance of nitrogen, posing a threat to the health of both terrestrial and aquatic life. The journal Atmospheric and Oceanic Science Letters (AOSL) published a special issue on May 21 dedicated to the topic, bringing together a collection of 13 papers that explore the cascading consequences of nitrogen increase in circulation.

The biggest human driver of nitrogen emissions into the air is food production. The global agriculture sector depends on ammonia-based fertilizers to prime the soil each season to grow new crops. Rain and artificial irrigation sweep much of the nitrogen-based fertilizer away, landing it in lakes and oceans and damaging aquatic ecosystems.

Combustion of biofuels and fossil fuels also releases enormous amounts of nitrogen into the atmosphere.

Atmospheric nitrogen is eventually returned to land and oceans via rainstorms, but emissions often far outpace the Earth's natural ability to cleanse the air. That ongoing cycle of excess nitrogen continues to drive the trend of reduced biodiversity, especially in oceans.

Dr. PAN Yuepeng, editor of AOSL and scientist from the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, said that the special issue advanced the scientific community's understanding of atmospheric transport of nitrogen and all its consequences. "It is imperative that we continue to better understand the flow of nitrogen compounds in and out of the atmosphere so policymakers can deliver more effective interventions," PAN said.

The AOSL series suggests that a next generation of studies on nitrogen deposition should further consider the impact of ammonia due to its increasing emissions from livestock waste, fertilizers, and fossil fuel combustions.

Previous papers derived their data mostly from field experiments involving spraying nitrogen solution onto soils, largely ignoring the direct impacts of ammonia.

Worldwide nitrogen emissions continue to grow. "This causes concern among the scientific community. Without further research and actionable interventions, more damage to ecosystems will likely occur. We've set the stage for further global research collaboration on this urgent issue," PAN said.