abbreviations used in this article:
C - carbon
C02 - carbon dioxide
H - hydrogen
N - nitrogen
NOx - nitrogen oxides
P - phosphorous
S - sulfur
SOx - sulfur oxides
"Thus human beings are now carrying out a large scale geophysical experiment of a kind that could not have happened in the past nor be reproduced in the future. Within a few centuries we are returning to the atmosphere and oceans the concentrated organic carbon stored in sedimentary rocks over hundreds of millions of years." Page 99, citing Roger Revelle and Hans Suess in the first issue of the earth science journal, Tellus, 1957 - nearly sixty years ago!
Carbon, as it cycles through the atmosphere, waters and biosphere
Despite its age this is a worthy reference text for the environmental activist's or permaculturist's library. It's subject is the biospheric cycling of essential chemical elements, how human agriculture and industrial activity have perturbed these cycles, and what the consequences are or might be. If we persist in disturbing the natural flows and cycling of vital nutritional elements upon which our physical existence depends, we should expect trouble..
Conversely, correcting our perturbation of cyclic elemental fluxes will solve - or alleviate - many of the problems we face today relating to food production, economic health, human health and, ultimately, geopolitical stability. All aspects of life, in short, are touched - visibly or invisibly - by these great natural cycles: they are physical bases of life itself.
Life, we read in our school biology texts, is a "cyclic" chemical phenomenon driven by solar energy: plants capture solar energy and use it to synthesize energy storing molecules (hydrocarbons: sugars, starches, fats and oils). Plants use this stored solar energy to grow and reproduce. Herbivores capture and exploit the energy flux of photosynthesis by eating plants. Carnivores, in turn, exploit the highly concentrated nutrients stored in the bodies of herbivores.
"In nature, nothing is wasted": excreted or dead matter is broken down by decomposers (invertebrates, bacteria, fungi) in order to capture residual energy and nutrient stores. The end result are simple energy poor molecules (water, carbon dioxide, methane, sulfur and nitrogen oxides..) Plants absorb these through their roots and leaves and assemble them into high energy life supporting molecules through the Living Alchemy of photosynthesis. Observe the cyclic movement of C: plant to herbivore to carnivore to decomposer and back to plant again. Energy: the energy stored in solar radiation (light) turns the wheel..
biospheric cycling of nitrogen
About 30 elements of the periodic table are (more or less) "essential" to life (some are more critical than others).
The Big Three: hydrogen (H), carbon (C) and oxygen (O). The basic energy storing molecules (sugars, starches, oils and fats) are called "hydrocarbons", reflecting the dominance of the Big Three.
C6H12O6 + 6O2 6CO2 + 6H2O + liberated energy
Oxidation of glucose - sugar. One molecule of glucose is "burned" with six oxygen molecules to form six CO2 molecules and six water molecules. When this reaction occurs in living cells (plant or animal), it is called "respiration". The energy liberated by the controlled burning of glucose is used for biological work: cellular repair, growth, movement, mental activity (sensation, thinking..)
Several other elements or types of elements (metals) are essential:
- Phosphorous (P) - storage / release of energy in convenient "packets" to power muscular contraction, neural activity and the synthesis of essential biochemicals.
- Nitrogen (N), Sulfur (S) - incorporated into structural proteins and enzymes (biological catalysts essential for triggering, controlling metabolic processes). Because of their high degree of biological activity and natural abundance, unwanted P, N, S compounds are often extremely toxic: ammonia (NH3) and hydrogen sulfide (H2S) are real killers.
- Iron and other metals are employed in electron (and energy) transfer processes which capture and transform energy into forms usable by biological systems. Examples: hemoglobin, a molecule transporting O to the whole body, found in the blood of animals. Chlorophyll is the green pigment of plants, responsible for the primary capture of solar energy in photosynthesis.
So what makes essential nutrient elements cycle in the first place? What turns the wheel? In short, energy. (Professor Smil's primary field of research is "Energetics" or the study of energy flows and transformations in natural and human built systems: ecosystems, cities, civilizations.. see note 1). Much cycling of essential nutrient elements is through non-living processes which derive their energy either from the sun or the "fossil" heat energy from earth's initial gravitational collapse stored in earth's core. Some core heat is also produced from the decay of radioactive elements (radium, uranium..) which liberates energy stored in the nuclei. Winds transport gases like sulfur or nitrogen oxides (SOx, NOx). Winds are actually a form of solar energy, driven by unequal warming of earth's surface by the sun.
The hydrological - water transport - cycle, consisting of evaporation, transport by wind and deposition as rain or snow, is driven by solar energy. When water evaporates it absorbs energy - heat - originating in the sun. Precipitation can dissolve and transport chemical elements.
Carbon dioxide dissolved in rain chemically "weathers" - erodes - rocks. This process is itself fairly complex with several feedback loops. It removes carbon (as CO2) from the air. It liberates mineral "fertilizers" necessary for plant growth (iron, potassium..). In the long run, weathering wears down mountains, sculpting the face of the earth. Some of the CO2 removed from the atmosphere by weathering ends up in flowing water as carbonate or bicarbonate ions (CO3, HCO3). These ions enter the sea, are absorbed into the shells of microscopic plants and the animals that eat them (plankton). When these organisms die, the shells fall through the water column. Most of the carbonate is dissolved or eaten before it hits the sea floor but a tiny fraction falls to the seabed as C - and O - rich sediment. Sediment accumulates over millions of years and is compressed by its own weight into sedimentary rocks. If uncompensated this burial - "sequestration" - of C and O would, in the long run, deplete the biosphere of C and O. However, what goes down must come up..
The earth's continents float on "tectonic plates", rock slightly "plasticized" by the core's heat and the overlying weight of rock and continents. Convective currents of plasticized rock, driven by the heat released from the earth's core, cause rock to rise and flow horizontally in places (mid ocean ridges). In other places, Japan, Chile for example, plasticized rock flows dive beneath continental plates ("subduction zones" responsible for the terrific earthquakes of Japan and Chile).
An active subduction zone. The chunk of lithosphere diving beneath the continental crust carries with it C and O rich ocean sediments. In the depths of the earth under high pressure and heat these sediments decompose into simple chemical compounds: CO2, water, methane, SOx, etc which are then reinjected into the atmosphere through volcanic "outgasing", completing the elemental transport cycle: air to biosphere to seabed and back to atmosphere. These slow cycles are measured in multi-millions of years..
Five of the essential nutrients - H, C, O, N and S - are said to be "doubly mobile", being transportable in liquid water and by winds. These highly mobile elements engage in short period, high flow rate cycles of limited geographical extent. A carbon atom may cycle rapidly within a tropical swamp for millennia, moving from plant to herbivore to carnivore to decomposer and back to a simple carbon molecule (CO2 or methane) before being reabsorbed by a plant. The cycle time may be of the order of months or years.
And the place of humanity in natural cycles? Early humans, few in numbers and technologically primitive, did not disrupt the cycling of essential nutrients very much. Estimates of the stone age human population range from a few hundred thousand to a million or so. These populations varied wildly according to climatic cycles. When local / regional climates took a turn for the worse - cooling, desertification.. - regional populations could be forced to emigrate - or die off. Like animal populations these early hunter-gatherer-(? scavenger ?) populations rose and fell with fluctuating environmental conditions. Only through human curiosity and ingenuity did human societies manage to impose an upward inflection on the environmentally driven fluctuations in numbers: improvements in hunting technology, tools, clothing and the various "revolutions": the discovery of fire, ceramics, agriculture, animal domestication, copper and, later, bronze and iron..
As late as the time of Christ, human population numbered no more than 200 to 300 million! To put this in perspective: the current world population is heading toward 7.5 billion, thirty times the world population at the height of the Roman Empire. Paradoxically, with this "tiny" population, the ancients managed to invent "civilization": law, government, writing, mathematics, the rudiments of the scientific method, literature, theater, art, architecture, philosophy, an irregular but augmenting pace of technological advance.. Perhaps our modern numbers, rather than being an asset, as some rosy optimists claim, are the millstone around our neck that will drown us..
The problem is twofold. There are many more of us in recent times, since the beginning of the industrial revolution, about two centuries ago. In addition, our individual environmental impacts have rocketed skyward during that time, compounding or increasing the impact due to population growth alone (note 2). To obtain all that energy - often employed wastefully or for frivolous ends - we burn massive quantities of fossil fuels (coal, oil, gas, peat..), upsetting the chemical balance of cycling nutrients with the gaseous byproducts of all that combustion: CO2, methane, NOx and SOx. In addition, industrialized farming with its massive dependence upon chemical fertilizers has upset the N cycle.
The crux of the problem:
"Since the 1950s some anthropogenic flows have come to rival the largest biospheric fluxes even on a global scale.. emissions of S from fossil fuel combustion and metal smelting now surpass the combined global production by bacteria and volcanoes..
The quantity of NOx we generate is at least equal to all natural flows.. all this reactive N is now providing surprisingly high levels of fertilization to natural ecosystems, a development.. with both welcome and worrisome consequences." Page 16-17
"Worrisome consequences": in the long run, as levels of anthropogenic emissions rise with population growth and industrialization of the Third World, the outcome of such meddling in nature's workings becomes increasingly unpredictable.
Likewise, fossil fuel combustion releases CO2 formerly "sequestered" in the earth's bowels. The amount released now "surpasses the rate with which oceans and plants can remove all this additional input from the atmosphere. The result is a steady increase in the atmospheric concentration of this most important anthropogenic greenhouse gas - and the possibility of global climate change". Page 17, emphasis added. (note 3)
The above citation deserves rereading: it gives the lie to one of the fallacies propagated by Global Warming "sceptics" and deniers. The annual amount of C released by human economic activities, transport, agriculture, etc is indeed "tiny" compared to the amount of C sequestered in the soil or to the annual photosynthetic / respiratory rate of (biological) C cycling. These facts are then falsely interpreted to argue that human emissions must be harmless. The "logic" is flawed for two reasons:
Fallacy 1- it is not the amount of anthropogenic C released each year that matters but the fact that the natural equilibrium is perturbed. The excess can no longer be absorbed by the biosphere, soil and waters with the result that that CO2 levels, while "tiny" are climbing rapidly, at an unprecedented rate.
This record from the Mauna Loa, Hawaii, observatory indicates that mean atmospheric CO2 levels have risen from 315 parts per million (ppm) in 1950 to about 395 ppm in 2015. That's 80 ppm on 315 ppm, a whopping, incredible 25% rise in a mere 50 years! The sawtooth pattern is due to the annual rise and fall in CO2 levels in the northern hemisphere caused by seasonal variations in photosynthetic activity. CO2 is absorbed in the warm months when plants are active and rises in the winter when plant life is dormant. Click on image for enlargement.
Fallacy 2- If CO2 were "neutral", innocuous, an imbalance in the global cycle of production and absorption would be less concerning, at least in the short run. But CO2 is not "innocuous". While not poisonous, it is a potent greenhouse gas (note 3), trapping solar energy in the lower atmosphere and disturbing the earth's natural thermodynamic (energy flow) balance. Climate and weather - driven by thermodynamic energy flows and equilibria - are perturbed with potentially disastrous results for world food production. Tradition agricultural systems - designed for traditional climates, weather patterns and extreme weather variations - could collapse if, say, the intensity and timing of monsoons were altered.
Current CO2 levels are way "out of bounds". Measures of "fossil" CO2 levels - from air bubbles trapped in glaciers - show that current CO2 levels are the highest in the last 130,000 years or so - since before the last ice age, way back in the warm Eemian Interglacial period when there were lions in London and hippopotamuses sported in the lakes and rivers of Germany.. Our current agricultural systems may end up as road kill if climate changes too rapidly for natural - and human - adaptation to occur.
Simplistic clichés propagated by global warming deniers and "sceptics" - "CO2 is not a poison, it is plant food".. - belie a profound (sometimes deliberate) ignorance of biological and ecological processes. Increasing CO2 indeed stimulates some ecosystems - for a while at least. Other ecosystems where C is not a limiting growth factor are not stimulated as much (or not at all). Plant species - and ecosystem types - are highly variable in their response to CO2 enrichment,.. And then, do we really want to "fertilize" the really nasty plants?
Ecosystems are complex, dynamic, interconnected systems which strive to maintain their internal integrity in the face of the slings and arrows of outrageous fortune: forest fires, floods, extreme windstorms, drought, killer frosts, epidemics, invasive species, climate change, loss of species.. Disturbing a self-organizing system (SOS) like an ecosystem leaves no lasting impact if the disturbance lies within the capacity of the system to adapt. There is much evidence today to support the claim that we are pushing our planet's biospheres beyond their "design limits" and that they can no longer adapt to the assaults humanity is unwittingly delivering. The risk is that a severely disturbed SOS - our planetary biosphere, rather than striving to return to its initial state of equilibrium, may collapse (rapid die off and drop in biodiversity, the number of resident species). The SOS may also "mutate" or "change state": one ecosystem type may be replaced by another, perhaps one inhabitable for many of the original inhabitants.
There is accumulating evidence that just such an ecosystemic collapse is occurring now:
half of terrestrial species go missing in (a mere) forty years
same thing for about 40% or so of the oceans' species in the last four decades
Something's wrong, very wrong..
Why is the late news starting to look like a Sci-Fi film? At the limit, climate change - induced by greenhouse gas emissions - may trigger ecological succession or collapse in stressed seas and soil in ways that may convert them from CO2 sinks - storing anthropogenic C - into C sources. They would then begin spewing billions of tons of CO2 and methane thereby amplifying the global warming which triggered the release of C in the first place! (Such a self-reinforcing loop is called "positive feedback".) The Siberian Times has been reporting mysterious "methane blow holes" in thawing permafrost. The permafrost thaws as a result of global warming. Bacteria feed on the thawed, now accessible, organic matter stored in the soil, generating methane and CO2. When enough gas pressure builds up fast enough, Boom!, it blows, creating a spectacular crater. Check out the photos in this link: would make a fantastic beginning for a Sci-Fi (or Horror) film. Now just what is lurking down in those craters..
Remember the descent into the hold of the alien ship in the movie Alien?
Nitrogen (N) and sulfur (S) also possess their store of jack-in-the-box surprises. NOx from combustion and outgasing from overfertilized soil react with other combustion by products to produce that potent urban witch's brew known as (photochemical) smog. The health impacts of this chemical soup are now too well known (think, Chinese cities!): lung injury, immunity problems, aggravated respiratory and cardiac illnesses, bleaching of dyes, architectural erosion; damage to textile, rubber, plastic, etc. All these constitute a hidden "pollution sur-tax" rarely included in conventional estimates of economic "development"..
There is still so much we don't know, so much we have to learn, and so little time, given the pace things are now unfolding at..
Consider, "blow back" or unintended negative consequences of actions. Attempts to reduce CO2 emissions by boosting combustion efficiency often show a N related boomerang effect. A more efficient - hotter - boiler for an electrical generating plant may indeed release less CO2 - and a lot more NOx! The same applies to car engines, making yet another argument in favor of investment in public transport: more passenger miles per unit of fuel consumed..
N runoff - from fertilizer - and deposition by wind is causing eutrophication - algal blooms - in coastal zones.
Algal blooms stimulated by fertilizer and sewer runoff can, eventually, lead to "dead zones". The water column, depleted of O from bacterial decomposition of all that excess organic matter, becomes anoxic (no-oxygen) and therefore incapable of supporting life, except for hardy decomposer bacteria. Worse, the water is tainted with poisonous hydrogen sulfide gas. Such dead zones can impact negatively on the economic and ecological viability of fisheries, essential sources of protein on an already over-populated planet. N is a good thing, too much - bad..
root nodules: symbiosis between plant and nitrogen-fixing bacteria
The symbiosis between leguminous veggies and N fixing bacteria allows the plant to absorb biologically inert nitrogen from the air, soil or water and convert ("fix") it in a reactive form usable for the plant's growth and metabolism. To do so, the plant feeds energy and nutrients to the bacteria in return for a "profit" on its "investment": N is often a bottleneck, a limiting factor, in plant growth and reproduction.
"Yet neither the biosphere's apparent record of resilience nor the successes of our more rational management guarantee a comfortable outlook. The great forces that have led to more than a century of rising interferences in biospheric cycles - the rapid growth of global population and its quest for higher standards of living - will only intensify during the next generation and will not slow down for at least another half a century. We are in the midst of an open-ended test of the compatibility of our civilization and the biosphere, and the test's most crucial stage is yet to come." Page 194
These words were penned nearly 20 years ago. Prof Smil placed the "test's most crucial stage" in the future. Today, we are there. The sh*t is now IN the fan..
"Since Vernadsky's death in 1945 some new and powerful trends - above all the information revolution and a strong tendency toward global economic integration and political cooperation - have given us new tools and means.. Are we now moving in the right direction, with our incipient attempts at managing the global commons through international treaties and cooperative agreements, with our attempts to preserve biodiversity, and with our thinking about sustainable economies?
Or are we entering a period of planetary disarray, during which the ever-present forces of self-destruction, and social and political disintegration, will be greatly magnified by the unprecedented damage we will have inflicted on the biosphere? Vernadsky's judgment regarding the long-term prospects for the biosphere was unequivocal. Shortly before his death, in a letter to a colleague written during the final months of World War II, he concluded:
I look forward with great optimism. I think that we are experiencing not only an historical change, but a planetary one as well. We live in a transition to the noosphere." Page 203
noosphere: a "new state of the biosphere" with a unified humanity serving as the thinking consciousness of nature. From the writings of Vladimir Ivanovich Vernadsky (1863 - 1945), a visionary Russian scientist who was one of the founders of the concept of the biosphere. Such thoughts have found a certain currency during the 20th century - predating the the economic "globalization" of recent decades. One could cite, among others,
- the French theologian Theilhard de Chardin: "noosphère" - the realm of ideas, taken collectively,
- James Lovelock, the inventor of the Gaia Hypothesis:"The Awakening of Gaia", humanity as the "thinking part of nature",
- Edgar Morin, French philosopher of self-organization theory: "noosphère" - same sense as Teilhard de Chardin,..
Vladimir Ivanovich Vernadsky - whole earth visionary
1- for a more recent and technical work on Energetics: V Smil: Energy in nature and society, Massachusetts Institute of Technology Press, 2008
2- As stated, the argument overstates the impact: third world energy consumption lags behind the "developed" world's. However, in recent decades the Chinese and the Indians are doing their damned best to catch up to our wasteful energy and material consumption habits so the general argument stands.
3- greenhouse gas, greenhouse effect: high frequency solar radiation (mostly visible light) passes through the atmosphere with little attenuation. It is absorbed by the earth, vegetation and dark ocean surface waters, heating them. The heated surfaces radiate infrared (low frequency) radiation. Unlike visible light, the atmosphere is quite opaque to some frequencies of the infrared spectrum. This hinders the flow of heat outward, toward space from the earth. Think of wearing a warm sweater on a cool autumn evening: it traps and slows the loss of heat (infrared) from one's body. This insulating effect has also been compared to the panes of glass in a greenhouse. They allow light to enter freely, being transparent to visible light. Inside the greenhouse the light is absorbed by the various surfaces - soil, plants.., heating them. The heat (infrared) from the heated surfaces is blocked by the glass and passes slowly. The result is that the temperature in the greenhouse is higher than the ambient air temperature outside. Like the glass in the greenhouse, some atmospheric gases are efficient infrared absorbers - they block the passage of infrared rays. The most efficient greenhouse gas is water vapor, followed by CO2 and methane (methane is on a volumic basis a more efficient infrared absorber than CO2 but CO2 wins out because it is present at much higher concentrations). Adding CO2 and methane to the atmosphere increases the atmosphere's heat trapping capacity causing global warming. (click on image for enlargement)