Carrying Capacity Depends on Soil Nutrient Level

Peter Salonius 
Scientists for Population Reduction

Impending energy scarcity is influencing Canada's forest industry to look at high nutrient slash ( foliage, and fine branches with large bark/wood ratios) from stem harvesting operations as a source of biomass energy. This will mine the nutrient capital of forest soils and degrade their productive capacity.

Canadians should decide in what proportions they wish to use the STEM WOOD harvest -- for pulp and paper, lumber or biomass for energy and as a source of industrial chemicals. Wood is becoming the new petroleum. Wood can be a renewable resource, if harvested responsibly. We can only use each unit of wood once, so that we will have to decide whether we continue to produce wealth by exporting most of our forest products OR whether some of the harvest, that historically has been directed to commodity markets, is to be used in Canada for the production of biofuels and energy cogeneration. We can not have our cake and eat it too.

As I see it the carrying capacity of the Earth's ecosystems is hinged, in the long term, on the supply of nutrients for plant growth. Of all the natural resource exploitative industries, forest harvesting and ocean fisheries offered the best possibility for long term sustainability. Currently, as we have fished down the marine food chain and mined the ability of the oceans to absorb our pollutants, marine productivity of food that is useful to humans has been at least temporarily diminished.

With the exception of a period of forest litter raking in Europe to augment depleted fertility levels on agricultural lands -- in the period before mining, chemical synthesis and long distance transport of fertilizers made raking unnecessary -- most forest harvesting has been confined to the removal of stems with slash being left behind. This forest harvesting appears to have been fairly sustainable, at least as concerns the maintenance of soil nutrients for plant growth -- although biodiversity and ecosystem stability appear to have been compromised in many cases.

As the momentum and impetus to remove smaller tree parts (nutrient rich branches and foliage) increases in response to the demand for forest biomass energy --- EVEN FOREST HARVESTING is becoming a soil nutrient mining endevour. The following argument traces human history in the context of the depletion of soil nutrients and the consequent erosion of long term carrying capacity:--

Human population growth has been due to the absence of effective top predators as well as to cultural changes that resulted in ever more abundant food supplies. Ecologists have shown that, without effective top predators, all animal populations overshoot the carrying capacity of their ecosystems and then they experience population collapse in repeating cycles that degrade the very carrying capacity and biological productivity of their environments. This carrying capacity degradation is more serious as the amplitude of overshoot cycles is more extreme.

Hunter-gatherers, before the advent of agriculture, were mainly controlled by starvation when their numbers overshot the carrying capacity of the ecosystems they inhabited. The populations of these ancient people and the animals they hunted behaved in a classic manner -- experiencing die-offs to levels below equilibrium levels when their numbers exceeded the food supply and then expanding above equilibrium levels as food supplies recovered in a repeating cycle. This dynamic served to maintain balance between humans and other species.

Humans have far outstripped any equilibrium levels as they have usurped the living space of almost all of the other species on earth, and completely eliminated many of them. We have degraded the productive capacity of most of the earth's ecosystems and are now proceeding to make more alterations to the earth's atmosphere, by our use of fossil fuels and forest clearing, than have been experienced naturally in the last 600,000 years.

The advent of agriculture allowed the human carrying capacity of the earth to increase by increasing the access to and consistency of supply of food by storage, as Abernethy, Bartlett, Hopfenberg, Pimentel and others have pointed out-- however as most agriculture is a soil-nutrient-depleting practice, even this carrying capacity increase would prove to be unsustainable. In the very long term, on most of the surface of the earth, only the hunter-gatherer human culture appears to be sustainable because human numbers are controlled by the productivity of self-managed, NUTRIENT- CONSERVATIVE forest and grassland ecosystems.

When soil productivity was seriously diminished by unsustainable soil-nutrient-depleting agriculture in a particular area and/or population numbers became excessive, the propensity of humans to migrate came into play as new lands were colonized and put under the plow.

Just about the time that the whole earth had been submitted to human patch disturbance and the practice of farming -- finite fossil fuels allowed geological energy to replace draft animal power and to facilitate the mining, chemical synthesis and long distance transport of fertilizers to replace those removed by soil-nutrient-depleting agriculture.

The completely unsustainable six-fold population growth from 1750 to the present was facilitated by displacing solar energy dependence with massive amounts temporarily available, geologically stored non renewable fossil and nuclear fuels. As these fuel sources are exhausted, in the future, we can anticipate the replacement of unsustainable population growth with energy-depletion-orchestrated economic and population collapse.

Albert Bartlett has said that "modern agriculture is the use of land to convert petroleum into food".

A glance at any population graph demonstrates that human populations, since the advent of agriculture 10,000 years ago, have not been oscillating around any equilibrium level. Global human numbers have increased steadily. Nothing has arrested the steady increase in human numbers, although the elimination of 1/3 of the people between India and Iceland in the 1300s, as a result of Bubonic Plague='black death', did make a very small dip in the curve before its inexorable increase resumed within a century.

Since 1750, when temporary supplies of exhaustible geological energy began to be used, the population graph has increasingly moved toward a 'straight up' trace with no impression having been made on it by such devastating events as World War II that removed 20,000,000 from the Soviet Union alone.

Humanity has been repeatedly warned, by Malthus in the 1700s and many others since that, in the absence of effective natural controls on human numbers, societal population controls must be established by mutual consent. Homo sapiens, the species with the large brain, and the capacity to foresee future consequences, has not (collectively) understood the need for the control of human numbers. People in affluent countries that are free of war confine their thinking to short term issues, while people in countries beset by food shortages and warfare concentrate on surviving day to day.

Peter Salonius

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