Sometimes when you win, you also lose. That's the case with synthetic nitrogen fertilizer, an agricultural miracle that helped feed a growing global population but also caused some pretty nasty environmental problems that we are still dealing with to this day.
To understand why synthetic nitrogen fertilizer was such a big deal, you'll need a quick biochemistry lesson. Plants need nitrogen. But most sources of nitrogen, like guano, saltpeter and by-products of coal production, offer a limited supply that isn't particularly potent. One untapped source was the air, which is 78 percent nitrogen, but for the vast majority of plants the element is useless in this gaseous form. That's where chemist Fritz Haber comes in. He figured out a way to take nitrogen from the air and transform it into ammonia, a compound of nitrogen and hydrogen that plants can absorb. The discovery led to the widespread use of synthetic nitrogen fertilizer, which helped improve crop yields, and, as a result, helped increase the world's population from 1.6 billion to 6 billion during the 20th century [source: Keifer].
So what's so bad about that? For one, fertilizers release nitrous oxide, a potent greenhouse gas, and nitrogen oxide, which reduces the atmosphere's ability to protect us from ultraviolet radiation and causes smog. Nitrogen runoff from agricultural lands has also created algal blooms that create huge dead zones in the world's oceans. And finally, Fritz Haber went on to make pioneering advancements in chemical warfare, which caused many scientists to protest his Nobel Prize in 1918 [source: Simpson].