Humans obtain metabolic energy by eating food. Nitrogen is required to grow food, but natural supplies of nitrogen for human purposes have been inadequate since the beginning of the twentieth century. The Haber-Bosch process, invented in the early 20th century, now provides a virtually inexhaustible supply of nitrogen fertilizer. This one invention is responsible for the existence of about half of the world’s population. That’s the good news. The other news is that most of this nitrogen (and additional amounts from fossil fuel combustion) is lost to the environment where it contributes to smog, greenhouse effect, ecosystem eutrophication, acid rain and loss of stratospheric ozone in a sequential manner—the Nitrogen Cascade.

This lecture will examine the impact of this increased N mobilization on the global N cycle by contrasting N distribution in the late-19th Century with those of the late-20th Century. It will review our understanding of the primary points of nitrogen loss to the environment, the impacts on people and ecosystems and the opportunities for an integrated nitrogen management plan at the local and national level.

There are numerous challenges facing society to optimize the use of nitrogen to provide food for the world’s peoples, yet minimize the negative consequences on the environment. A key challenge is how scientists communicate the issues concerning nitrogen to both the public and to policy makers. The talk will conclude with some suggestions in this regard.