If I told you that there was a global environmental cycle that humanity had seriously affected, with potentially catastrophic effects, you’d say, “Sure – the carbon cycle; carbon dioxide and methane emissions causing global warming and ocean acidification.” And then I’d say, “No, I’m talking about the one where humanity’s influence has been even bigger than that.” And most of you would give me a blank stare. But there is such a cycle, although it’s only been reported on piecemeal in the media. It’s the nitrogen cycle, and our activities have emitted nitrogen containing compounds on such a scale that 70 percent of the reactive nitrogen compounds circulating between the atmosphere, earth, and sea are of human origin; for comparison the climate change discussion revolves around a 10 percent increase in atmospheric carbon dioxide.
“So why haven’t I heard about this sooner?” you might ask. Well, you have, but only in bits and pieces; today we’re going to try and connect the dots on this issue. Some of the pieces you’ve heard about include: “dead zones” in the oceans, algal blooms, acid rain, nitrate in drinking water causing “blue-baby” syndrome in agricultural areas, smog and asthma, factory farming, and more – even, as we shall see, overpopulation. If you’ve never understood why environmentalists say, “everything is connected to everything else,” you’re in for an eye-opener today.
Do I have your attention now? I thought so. Follow me over the fold.
This is another installment in the New Environmentalism series, where we both look at global issues and suggest actions you can take for yourself to help address the problem. Egarwaen and I encourage you to contact either of us by email if you’d like to be a contributor to this series (post a diary or host a discussion).
First let’s take a step back and describe the nitrogen cycle the way it used to operate, and then look at the way it’s trying to cope today.
Nitrogen is essential for all living things – it’s an essential component in every amino acid that make up your proteins, and in the molecules that form the “rungs” on the DNA ladder that control heredity. In the center of every molecule of chlorophyll, four nitrogen atoms hold a magnesium ion in place to capture sunlight and power life on earth. In the center of every heme molecule, the same four-nitrogen-containing ring (called a porphyrin ring) contains iron, which binds oxygen in animal blood to carry it throughout the body. This same porphyrin ring holds a cobalt atom in the active part of vitamin B-12, as well.
But nitrogen is an inert gas, making up 78% of the atmosphere – and good thing, too; it’s the nitrogen that keeps the oxygen in the air from setting everything on fire at the first spark. This inert gas has two ways of forming more reactive forms that can interact with life. One is lightning, which naturally forms nitrates (NO3) by combining nitrogen and oxygen. The other is by certain soil bacteria, called nitrogen-fixing bacteria, which convert nitrogen in the air into ammonia (NH3).
Ammonia is then converted by nitrifying bacteria first into nitrites (NO2) and then into nitrates (NO3). Some of the nitrates are absorbed by plants; some of the nitrate is converted by denitrifying bacteria and fungi back into nitrogen (N2) in the atmosphere.
The nitrogen taken up by plants, as well as the nitrogen incorporated into animals that eat the plants, eventually return to the soil when the plant or animal dies, and in its wastes. There, decay stepwise releases the nitrogen as ammonia again, feeding back into the cycle.
This cycle still occurs, but human activities have distorted the flows for a century now, since Fritz Haber, a German chemist, discovered how to convert nitrogen and hydrogen into ammonia in a chemical process that bears his name. This discovery had two immediate effects: it allowed mass production of chemical fertilizers, greatly increasing food production and saving millions from the starvation that had always plagued humanity (for which he won the 1918 Nobel Prize). And it allowed mass production of explosives, costing millions of lives. [Prior to that time, both fertilizer and explosive production depended on rare mineral deposits of nitrates – saltpeter – found only in dry deserts (as the salts are water-soluble), or on deposits of bird or bat droppings (known as guano), which are rich in nitrate. Finding, claiming, and exploiting these resources was a major objective of the age of exploration; why else go to remote parts of Chile or isolated oceanic islands?] The Haber process prolonged WWI, and made WWII possible.
But it is the effects of industrial fertilizer production and use that are of interest to us here. The first effect was to allow the “green revolution,” especially since WWII, when petroleum was plentiful enough to power the Haber process on a massive scale (plus, those factories that had been churning out explosives had to find a new use for their products, or face bankruptcy). Cheap fertilizers (and higher-yielding crops) led to a jump in the human food supply. And like any other animal, when there’s more food, the breaks keeping the population in check are loosened – until the population grows to the point where the limits are being pushed again. This is what Malthus first brought to general public recognition.
Unfortunately, the extra nitrogen added to farm fields has overwhelmed the ability of denitrifying bacteria to convert it back into nitrogen gas in the atmosphere, throwing the system out of balance. The extra nitrogen then can seep into groundwater, to be taken up in drinking water wells in agricultural areas. This causes methemoglobinemia, or “blue baby syndrome.” Nitrates are converted in the body to nitrites, which interfere with the ability of hemoglobin to carry oxygen in the body (hence the blue color). The condition causes headache, fatigue, breathing difficulties, diarrhea, and vomiting; extreme cases can result in loss of consciousness and death. This is a serious problem in parts of the US and the Netherlands.
Or the nitrogen, say from animal feedlot operations, goes into the air. Ammonia reacts in the air with nitric acid to form ammonium nitrate, a solid. Tiny particles of this hang suspended as particulate air pollution, contributing to asthma and other breathing difficulties. The San Joaquin valley in California produces 20 percent of all the milk in the US, and there are now (controversial) plans to regulate emissions from farms that contribute to this air pollution.
I say, “contribute to” because there is also the effect of burning fossil fuels, including in cars, which I haven’t yet discussed. Burning fossil fuels – which also has grown massively in the last century, especially since WWII – also releases nitrogen compounds to the atmosphere. These contribute to smog, and react with water in the air to form acids that fall as acid rain. Another nitrogen compound, nitrous oxide (N2O, which you may know as laughing gas) is also released in combustion. While there’s not a lot of it, relative to other nitrogen compounds (it’s presently at 311 parts per billion in the atmosphere, compared to 360 parts per million of carbon dioxide), it has its own set of problems. For one thing, it is over 300 times as potent a greenhouse gas than carbon dioxide. For another, it contributes to the destruction of the ozone layer in the stratosphere, which protects the earth’s surface from over-exposure to harmful levels of solar UV rays. [This is the link between the ozone layer and greenhouse gases that seems to cause so much confusion. The main greenhouse gases (carbon dioxide, methane) do not connect into ozone depletion issue nearly so directly.]
Globally, five times as much reactive nitrogen comes from food production as from energy production, as it’s much harder to meter nutrients to crops precisely. While there is an obvious economic disincentive to burning more fuel than you need to, there is a less easily measured disincentive to letting excess fertilizer run into a creek, and no disincentive at all for animal waste runoff.
Which leads to another pathway for farm runoff we’ve not examined: farm runoff – both of fertilizer applied to crops, and from the wastes of farm animals – can enter streams, rivers, and eventually the ocean. And here the effects of our distortions on the nitrogen cycle tie into everything we discussed a couple of weeks ago in the ocean discussion.
Eutrophication is the term for what happens to a body of water when it is “over-fertilized.” There is an algae bloom as the algae react to this new, rich “food source.” Then the algae die and fall to the bottom, decomposing and using up all the available oxygen. This creates the infamous “dead zones” found at the mouths of major world rivers. The Mississippi may be the best-known case, but there is a significant dead zone in Chesapeake Bay, too, from the Potomac River to the bay bridge.
Now, lack of oxygen in the bottom of the Chesapeake is a serious problem, as that is where the oysters that filter much of the excess nutrients from the bay’s water live. And, in fact, the oyster population in the bay is now about 1% of what it was a century ago (Which likely was, in turn, reduced from what it was in the pre-colonial period). But the oyster isn’t the only mechanism for cleaning the waters of Chesapeake Bay; they have a partner in the form of the “sheep of the sea” – our old friend from the other diary, the menhaden.
In case you missed the other diary, menhaden are small oily and bony fish that are no good for food, but which can be harvested for their oil and protein (used as animal feed for chickens and hogs, in a harmful feedback to the oceans), and are being over-harvested. Remove too many menhaden and the only thing you have left to eat the plankton and algae blooms are jellyfish (who are able to survive in the “dead zones” as well). Now you know why there are so many jellyfish recently…
On the other hand, if the chickens and hogs are fed on soybean-based feed, not only are the menhaden spared, but additional leguminous plants are grown: Soybeans are one of those plants (legumes) that have nodules on their roots full of nitrogen-fixing bacteria, so they don’t need nearly so much nitrogen fertilizer applied. An unanticipated double positive feedback! There really is very little reason to maintain a menhaden fishery – we need the menhaden population to rebound both to feed on algae and remove nutrients from the coasts, and to serve as food fish for the other, larger over-fished species of predator fish that we humans do like to eat.
OK, you’ve convinced me that everything is connected, but now I’m totally depressed – everything is going to hell in a hand basket. What can I do about such a mess?
Fortunately, the same interconnections that make the news seem so bad mean that virtually anything you do starts to have helpful effects that ripple throughout the planetary ecosystem. That is a key point that we often lose sight of, so I’m going to repeat it: Everything you do has positive effects that ripple throughout the entire ecosystem. If you remember nothing else from this diary, please remember that one sentence. Drive less? Turn down the thermostat and turn off the lights? Buy compact fluorescents? All reduce fossil fuel use, affecting things through all the links above (that I won’t list again for the sake of space).
Don’t fertilize your lawn – there are plenty of non-grass plants that will do fine in whatever soil you’ve got. [Here in east Tennessee, miniature strawberries and moss seem to predominate among the “weeds” in my lawn. What’s growing in yours?] If you (for some reason I can’t fathom) have to have the grassy monoculture, don’t fertilize unless you’ve had your soil tested. Then apply the minimum amount of fertilizer recommended. I would strongly encourage you to look into organic lawn fertilization, as this helps build up the microscopic ecosystem in your lawn that chemical fertilizer strips away. I’m not saying that chemical fertilizer is bad because it’s not “natural;” I’m saying it’s harmful because it provides too concentrated and too sudden a load of nutrients all at once, throwing the self-sustaining ecosystem on your doorstep out of balance. It’s the same as on a farm field (or golf course!) only written smaller. For similar reasons, buy organic and grow organically when you can.
Taxes on fertilizer are a possibility, but are likely to be politically impossible to pass. Removal of agricultural exemptions from pollution regulations would seem somewhat more feasible, as a “leveling the playing field” idea. It still won’t be popular in rural areas, but could be coupled with funds to support measures to address nitrogen pollution from agriculture.
It’s been found that greenbelts of forest can help capture excess nutrients, keeping them out of streams and even helping remove them from the air. If you farm, or live in a farming area, this is especially important. Likewise, urban greenbelts are important in keeping excess nutrients (including Fido’s poop, if you didn’t scoop) from streams there.
Eutrophication caused the “death of Lake Erie” a generation ago, and major progress has been made in addressing the pollution issues that caused eutrophication of the Great Lakes. Nature does have an immense capacity to heal. But we must establish the conditions that allow healing to begin. It is possible, but it takes will, it takes enforcement of laws and regulations already on the books, and perhaps some new approaches as well, such as conservation set-asides.
There are other ideas we can explore in the comments as well. But I want to close by re-emphasizing the point I made above: Since everything is connected, everything you do helps everywhere. There are positive feedbacks in nature, some science hasn’t fully elucidated yet, which will help in healing our ecosystems. There is hope.
Or, if we let things just go on as they are, there is the Malthusian solution. Malthus’ ideas weren’t killed; they have just been exiled for now, until the cheap and plentiful energy supplies run out. Then, we’ll have to face not only transportation problems but food availability issues as the price of fertilizer rises beyond the reach of most of the world’s people. A rather unpleasant way (to put it mildly) to get from our population of 6.5 billion back down to a sustainable level of under one billion. Widespread introduction of more intensive, organic farming techniques can help with this problem, but I expect it to be a hurdle we as a species will only clear with difficulty as this century plays out.
Recommended reading:
Net Losses: How a football tycoon took George H. W. Bush’s oil company and used it to declare war on the fish that built America by H Bruce Franklin, Mother Jones, March-April 2006
Something in the Air: Just when the world has started to take carbon emissions seriously, along comes another global threat. And this one could be even worse. by Rowan Hooper, New Scientist, 21 January 2006.