All life depends on nitrogen. The odorless, tasteless element provides the foundation for the essential acids and proteins that comprise all living organisms and the vast majority of the earth’s atmosphere. Nitrogen is a vital component of single-celled organisms, as well as plants and people.
But today, because of changes over the last century, there is too much nitrogen in our ecosystem and it’s creating serious issues with air, climate and water quality.
One person digging into the "why’s" and "how’s" of nitrogen proliferation is UNC Charlotte microbiologist Martin Klotz.
"We have begun to witness over the last couple of decades that the global nitrogen cycle is really getting out of balance," Klotz said. "It’s now in a state where the amount of fixed nitrogen is 3.5 times the level of naturally occurring nitrogen."
In 1909, chemist Fritz Haber developed a method to "fix" nitrogen, a process that involves taking nitrogen atoms from the atmosphere and joining them with atoms of hydrogen. Before Haber embarked on what has been dubbed the largest geo-chemical experiment ever attempted in human history, the fertility of the soil depended upon a natural process whereby soil bacteria living in the roots of legumes "fixed" the nitrogen. Likewise, oceanic life relies on microbes to supply the nitrogen they need to live.
– Martin Klotz, Microbiologist
The growth of the human population depends upon the fertility of the soil and the oceans; until Haber figured out a method to fix nitrogen, food production in the world had maxed out, and the population leveled off at 1.6 billion.
The Haber-Bosch process, as it is known, gave birth to the production of ammonium nitrate fertilizer, the catalyst for modern agriculture.
Without having to wait for the land to replenish itself, people were able to grow more crops — more crops equates to more people. Since Haber-Bosch the human population has skyrocketed to more than six billion, and growing.
"Haber-Bosch was really a game changer," Klotz said. "What we see now is that the input of ammonium fertilizer is creating a situation where organisms change their lifestyles and produce certain compounds in larger quantities than were normally produced."
One of these compounds is nitrous oxide, or laughing gas, which is mostly created when synthetic fertilizer washes from farms into rivers, streams, and then oceans, where it undergoes a chemical change facilitated by microbes, finally ending up in the air as nitrous oxide.
Some of it evaporates into the air where it acidifies the rain and contributes to global warming. In fact, nitrous oxide lingers in the atmosphere three times longer than carbon dioxide, accumulating in the stratosphere and destroying ozone. It has been identified within the past decade as the most worrisome contributor to global warming.
With a multi-year research coordination grant from the National Science Foundation, Klotz has worked to unite the scientific community in the quest to understand the nitrogen cycle. The funding enabled researchers from the United States, Europe and Asia to form the "Nitrification Network," thus opening up avenues for resource and data sharing, training and communication for scientists studying the nitrogen cycle worldwide.
Network scientists recommend a multi-pronged approach that includes funding to support basic research into the mechanisms that lead organisms to move electrons in the nitrogen cycle one way or another, creating compounds that produce both toxic and non-toxic by-products.