Without industrially created fertilizer, a third of the world's population would starve to death. Since Fritz Haber and Carl Bosch came up with a way a century ago to wrest nitrogen from the air and turn it into fertilizer for plants, food supplies have exploded.

But a lot of fertilizer applied to cropland simply washes off and fertilizes blooms of algae instead. When the bloom dies, other microbes move in to feast, in the process sucking all the oxygen out of the surrounding waters. The result: dead zones that lay waste to any sea life that could not flee. And such dead zones are proliferating.

Now research shows that a vast store of nitrogen is waiting in the soil to create new dead zones for decades to come. French scientists traced nitrogen fertilizer and found that roughly 15 percent of the nitrogen applied in 1982 was still sitting in the soil today. Their report is in the Proceedings of the National Academy of Sciences.

The research suggests that existing soil nitrogen could continue to flow to the sea for decades. A good reminder that our actions today have environmental consequences that our grandchildren will have to deal with.

—David Biello

[The above text is a transcript of this podcast.]