Wednesday, November 5, 2008

Soil Fertility and Carrying Capacity

Earth, the living planet
Earth's life-supporting environment was created by the very life dependent upon it. It is a symbiotic relationship with both halves of that partnership critically dependent upon the other. Without earth's benign and supportive environment there would be no life. Had plant life never arisen the oxygen atmosphere upon which all animal life is dependent would not exist.

As we near the end of our fossil-fuel age, the heartbreaking truth we must endure is that our dream of reaching out to the stars is likely never to be realized. We evolved as an earthbound species and will, I believe, be forever constrained to that reality. We, myself included, desperately want to believe there are other planets teeming with life. The reality is that, despite an incessant search, the only planet in all the universe that we know contains life is our own earth.

Like so many others I desperately wish SETI would receive that elusive signal from other intelligent life. Perhaps that would convince us all of what we have in common, that we are one us in a universe of them. But there are so many more reasons that we will never receive that signal than reasons that we might. Regardless, the reality is that we will continue to be dependent upon this planet for our existence.

Our solar system is a closed system. Our earth is a semi-closed system, receiving input from only our sun as it, like all stars, slowly consumes itself. The resources this planet contained before life arose are finite. Most of the resources since created by earth's living processes are renewable, not infinite but perpetually recreated by living organisms. Most of those renewable resources are themselves created from earth's finite resources. Life constantly recycles those elements through one living organism after another.

Converting inorganic matter to organic
Some of those organisms convert raw minerals and other elements into a form that they themselves and other organisms can utilize. They are made available to the roots of plants which make them available to animal species who eventually return them to the soil when they die. Then the microorganisms start the process all over again. Nature wastes nothing.

Life is still critically dependent on these organisms for extending and maintaining the carrying capacity of the planet. Every ounce of raw planetary resources converted by them to a bio-available form extends and maintains the amount of life this planet can support. In these first few billion years of terrestrial life the most readily available and easily obtained of these finite resources have continuously been drawn upon by earth's life forms.

All finite, non-renewable resources being consumed will eventually be used up, at least in their native form. Consumption will generally be at it's maximum at the point where about half of that resource has been used. This is the peak, just like Hubbert's Peak which describes the point of maximum consumption of the world's crude oil supply. Oil, though created from living organisms, is a finite resource. It is renewable only in that the same processes that created the oil we now use can recreate it. But the timescales involved are so long, on the scale of millions of years, that in human terms we must consider oil finite. I am, of course, discounting the abiotic oil theory which argues that oil is continuously created in the earth's mantle.

Resource dependence
The agent using a finite resource builds a dependence on it consistent with the rate at which that resource is being consumed. That dependence is at maximum when consumption is at maximum, when that resource has reached peak and is half used up. As that resource passes peak and its availability declines so too will the agent responsible for its consumption. That is not limited to finite resources. Dependence can also be built around a renewable resource. The number of Koala an area can support is dependent on the rate at which the Eucalyptus trees on which they feed reproduce. Pandas are dependent on the reproductive rate of bamboo. Cheetah's rely on the breeding rate of Thompson's Gazelles. Oil can be reproduced but the rate of regeneration is far exceeded by the rate at which we humans consume it.

We consume and destroy earth's resources at a rate far exceeding that of all other life forms on the planet. Our activities, unlike those of any other species, are systematically destroying the life-support capability of the planet. Vigorously carried on long enough we will destroy the planet's ability to support any life at all, ourselves included.

Life's critical dependence on top soil
Earth's life-support system consists of various components and sub-systems like the water cycle and the carbon cycle. The one component, however, most critical to land-based life, the engine of their life-support system, is top soil. That is the thin layer of dark, organically rich soil in which plants spread out their roots and upon which animals walk, urinate, defecate, give birth and die. It is in this thin, vital layer of soil that microorganisms convert raw resources and make them available to the myriad forms of life around and above them.

The human body contains trace amounts of almost every mineral on earth; carbon, calcium, sulfur, phosphorus, potassium, gold, silver, zinc, copper, iron, aluminium, molybdenum, chromium, platinum, boron, silicon and more. These are derived from the soil through our food. The amino acids that our body's proteins are made from contain only carbon, hydrogen, oxygen, nitrogen and sulfur. Our bones are constructed mostly of calcium, silicon, and boron. What are all of those other minerals used for?

Enzymes and Hormones in living organisms
All living organisms are vitally dependent on two particular types of proteins that control metabolism, conversion of food to cellular material, functioning of the nervous system, cell regeneration and more. Hormones are the body's internal messaging system. They control, for example, your body's rate of cell reproduction that controls your growth, your nervous reactions, cell division, immune responses and the contraction of muscles. Enzymes are responsible for the conversion of material from one form to another, the physical construction, maintenance and division of cells, the conversion of glucose to energy, and much, much more. There are literally tens of thousands of different types of enzymes responsible for virtually everything that happens in your body.

Enzymes and hormones are built to exacting specifications contained in your DNA. An enzyme may be responsible for combining together a carbon atom and an oxygen atom or splitting apart two joined sulfur atoms united by a disulfide bond. Each does only one very specific function. Most enzymes require a catalyst that acts as an agent in speeding up a chemical reaction (getting the carbon atom and oxygen atom to link or getting the two sulfur atoms to separate). These reactions would otherwise take place at such a slow rate that life could not function. Movement would not be possible. Your body would be unable to build replacements for your damaged or worn out cells. Food could never be transformed into usable material in your body or converted to energy to drive your muscles and nervous system. Enzymes quite literally are the key to life.

You may be aware of the handful of your body's digestive enzymes. But most of the tens of thousands of enzymes in your body are contained within your cells. They are generated there, do their function there, are broken down and recycled there, never exiting the cell in which they are created. Your food may be acted upon by hundreds, even thousands of different enzymes (like workers on an assembly line) from the time it enters your mouth until it is used in various bodily processes or built into a cell.

How catalytic enzymes function
The key to the enzyme's ability to do it's job, like the assembly line worker, is the tools it has to work with, the catalysts. That catalyst may be a particular vitamin, an atom of oxygen, or more likely an atom of a particular mineral like iron, gold or silver. The minerals in your body not used in the structure of your bones, cells, nerves and muscles are used by hormones or by enzymes as catalysts in completing the chemical reaction they are responsible for. Without it's required catalyst, like the assembly line worker without his tools, the enzyme cannot do its job. If one enzyme in a series of reactions doesn't work the whole series of events shuts down. The enzymes after that can't get their materials. If the body, for example, does not have functioning amylase enzymes which break down starches, all of the bodily functions dependent on the nutrients in starches will not be able to function because their materials are, in a sense, held up at the receiving dock.

It is through our food that we get all of the minerals and other substances that our enzymes and hormones need as building materials and, most importantly, as tools to do their work. The body may still be able to generate the enzymes from instructions contained in the DNA but without their catalysts they are as productively useless as the workers sitting in the cafeteria.

Destruction of critical soil micro-organisms
Plants get those minerals from the soil through the help of an army of microorganisms that convert them into a form, very often an oxide, that the plant can use and making them available to the roots of the plant. We are systematically destroying the microorganisms upon which all life is dependent and the overall fertility of our soil. We are doing so;

* through our use of agricultural pesticides which kill soil organisms as well as the insects and other pests that we intend to destroy,
* through intensive deforestation resulting in millions of tons of critical top soil (and the microorganisms and minerals in that soil) being eroded away,
* by exposing forest soil microorganisms that break down dead and fallen material on the forest floor to construct new soil,
* through intensive irrigation which leaches vital mineral content of the soil down to levels where it is no longer accessible,
* with air pollution which results in toxic chemicals being absorbed into the soil where it kills those microorganisms,
* with industrial scale plowing and tilling of the soil resulting in millions of tons of top soil being dried up and blown away every year,
* by creating an impermeable layer of hardpan just below the top layer of soil which prevents both plant roots and soil microorganisms reaching the mineral nutrients in the subsoil,
* in turning over the soil with the plow which brings deep topsoil organisms to the surface where they are killed by exposure and driving aerobic microorganisms from the top layer of soil deeper underground where they are killed for lack of air, water and heat from sunlight,
* with our systematic destruction of the balance of soil nutrients through continued application of artificial fertilizers containing only nitrogen, potassium and phosphorus,
* by systematically changing soil ph levels which makes it an inhospitable environment for many of these critical soil organisms,
* by systematically changing the symbiotic relationships of soil organisms and plants by destroying the native variety of plants and replacing it with massive tracts of monoculture.

Clearly we cannot continue the destruction of this life-support capability upon which we and all other terrestrial life depend. We must begin making drastic changes now, before it is too late. Sooner or later we will push that system to a tipping point beyond which recovery is not possible. We do not know where or when that tipping point will be. We can only hope that we have not already passed it but we must still proceed with the assumption we have not.

Focusing on food security
The focus of our effort must be food security. The most critical aspect of our ability to feed our massive population is soil fertility. We must ensure that the balance of the mineral and other elemental content of our soils is rebuilt and maintained and that the soils are repopulated and maintained with the critical microorganisms that convert those elements and make them available to the other living organisms, including ourselves.

We cannot use those processes that allow us to feed over six billion people but destroy earth's life-support capability and at the same time help the planet regain it's optimum carrying capacity. The two are mutually exclusive. The longer we use those destructive processes the greater the risk we will push the life-support system beyond the tipping point leading to its eventual and inevitable collapse.

If we pass that tipping point the worst-case scenarios of population collapse become increasingly probable. The global population will inevitably contract, with or without peak oil, with or without global warming or any of the other global crises looming on the horizon. When and how badly depends upon how soon and how seriously we begin to rectify the problems we have created and move toward a sustainable modality of interfacing with this planet's natural systems. Continuing to push the limits of that life-support system while continuing to live in denial of that reality almost guarantees the worst possible outcome, eventually.