The Trickle-up Effect: Reducing the Bay's Nitrogen Will Lower Greenhouse Gas Level

A tale of two gases: both colorless, odorless and essential to life; now also both imperiling life as humans boost them to unnatural levels.

Carbon dioxide (CO2) gets the most press, though it's a mere trace of Earth's overall atmosphere, at about .04 percent. But that's now around 40 percent higher than natural, enough to risk calamitous climate change if we don't soon change our habits.

Nitrogen virtually is the atmosphere, some 78 percent of it. Humans have dramatically increased the amount that is biologically available to Earth's lands and waters—now twice the natural level—overfertilizing and degrading the Chesapeake Bay and other coastal waters worldwide.

If there's good news here, it's that resolving our excesses of these two very different elements often involve similar actions. So a climate change denier bent on restoring the Chesapeake Bay would almost have to support big reductions in CO2. Climate warriors who wouldn't know a sook from a jimmy crab will nonetheless be helping to revive our oxygen-poor estuary.

The most straightforward synergism with CO2 and nitrogen is the burning of fossil fuels to power our industries, run our vehicles and heat and cool our homes.

It's the biggest driver of climate change, releasing CO2 that traps the planet's heat, which in turn destabilizes climate. It's the second biggest source of excess nitrogen, stripping it from its inert, harmless dinitrogen (N2) form in the atmosphere to create the nitrogen oxides that poison the Bay—and our lungs.

Burning coal in particular is also a major source of the mercury that has led to so many health advisories on eating everything from crappie to largemouth bass and walleye around the Chesapeake region.

Reject fossil fuels, save the Bay, save the world—same same.

"Trees are the answer," my forester friend Larry Walton always said. Indeed, they sequester carbon, buffering the Bay against nitrogen. And they are way better looking and more full of life than parking lots.

So plant and protect trees Baywide/worldwide for those reasons—and increasingly to solve another problem of climate change. Our weather is projected to become "flashier," meaning with more intense rainfalls (Maryland's Ellicott City comes to mind) and more intense droughts.

Forests let the rains soak in and meter them back through groundwater during droughts, in effect stabilizing the Bay against flashy weather better than any other land use.

Agriculture is the Bay's leading source of polluting nitrogen, covering about a third of the watershed. It was the invention a century ago of the Haber-Bosch process —industrial-scale extraction of nitrogen from the atmosphere for fertilizer—that made farming a major source of excess nitrogen in coastal waters worldwide.

The way we manage ag land can have significant, positive benefits for keeping nitrogen out of the water and CO2 out of the air—minimal plowing, winter plantings of cover crops after the harvest, and vegetated buffers between farms and waterways can help with both.

Online calculators are a good way to see the carbon/nitrogen overlaps. Many are familiar with the ones that let you plug in your lifestyle and tote up your individual CO2 "footprint." Recently, the University of Virginia and the Chesapeake Bay Foundation have devised the first nitrogen calculators (go to or to the CBF website).

A cautionary note: My students at Salisbury University figured out that a very low-nitrogen, Bay-healthy diet would be vodka and french fries three times a day.

That is so bad for human health that it might actually solve the biggest and least talked-about way we can get CO2 and nitrogen reductions: stabilizing and reducing population.

Deciding to have one fewer child cuts CO2 by 60 tons a year, versus about 2.5 tons saved by going car-free, one ton by going veggie and a quarter ton by recycling, according to a 2017 Science Magazine study.

I haven't seen similar numbers done for population and nitrogen. But people have to eat, and given agriculture's big contribution to excess nitrogen, I'd expect an impact similar to CO2.

In fact, a critical difference between our two chemicals of concern is that, while we can legitimately strive for a prosperous society that is virtually carbon-free, we will always need lots of nitrogen to feed ourselves, maybe more than we use now, given hundreds of millions of people who are malnourished now and a population projected to add billions more.

Next there's heat—not just the hotter days that climate change predicts, but warmer water already witnessed in places like the Chesapeake Bay. Warmer water is already threatening eelgrass, a valuable aquatic habitat. It's also going to make oxygen depletion in the Bay worse and toxic algae blooms more likely—all this in combination with excess nitrogen.

Back on land, hotter weather means more heat-related deaths, particularly in cities. Stepping up urban tree planting both cools cities and absorbs CO2 and nitrogen.

Finally, there's a lot we don't know about the combined effects on the nature of more CO2 and hotter weather—the two may offset one another in some cases. Throw nitrogen into the mix and calculating impacts can get even more complicated.

Generally though, the message is clear: Healthy Bay, healthy planet—two for the price of one.

Tom Horton has written about Chesapeake Bay for more than 40 years, including eight books. He lives in Salisbury, where he is also a professor of Environmental Studies at Salisbury University. His views do not necessarily reflect those of the Bay Journal.

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