New Science Tracks Industrial Agriculture’s True Climate Impact

While we know that excess fer­til­izer escapes farm fields as gas, exactly how much and where it goes has largely been a mys­tery. But it has been a mys­tery worth solv­ing, as the amount of nitrous oxide — the third most potent green­house gas behind car­bon diox­ide and methane — in the atmos­phere is increas­ing fast. In fact, it has risen by 20 per­cent since the Industrial Revolution, with a good part of that increase com­ing in the last 50 years. For the sake of com­par­i­son, atmos­pheric car­bon diox­ide rates have increased around 40 per­cent in the same period. But nitrous oxide is around 300 times more potent as a green­house gas. And it’s also a major ozone-depleting chemical.

Pinpointing the cause of these nitrous emis­sions has been made espe­cially dif­fi­cult by the fact that every mol­e­cule of nitrous oxide looks alike. And there are so many sources — from microbes in farm fields, oceans, and nat­ural land­scapes to oceanic phe­nom­ena and human activ­i­ties like rain­for­est destruction.

As a result, it has been impos­si­ble to know just how much is com­ing from fer­til­izer use; and Big Ag has never been made account­able. But that may have all just changed.

Now, a group of sci­en­tists at the University of California, Berkeley have found a way to “fin­ger­print” var­i­ous sources of nitrous oxide — and they’ve deter­mined that the accel­er­ated increase in atmos­pheric nitrous oxide in the last few decades has indeed been due to syn­thetic nitro­gen fer­til­izer use.

The researchers accom­plished this feat through a fas­ci­nat­ing tech­nique — using a nat­ural “archive” of air frozen in Antarctic ice com­bined with an actual archive of air sam­ples taken from a (stun­ningly beau­ti­ful) pol­lu­tion track­ing sta­tion in Tasmania, Australia.

Click here to read the rest of this arti­cle at Grist.org.