By: Arthur Campbell
Al Gore's documentary film, "An Inconvenient Truth" is helping to make Americans more aware of the challenges they and the rest of the world face in the very near future, as carbon dioxide levels rise at a staggering pace. While discussions of greenhouse gases, global warming, and the Kyoto Protocol have been going for some years now, Gore's film is making all of these concepts far more concrete for the average citizen. The fundamental environmental mechanism at the base of all these discussions is the global carbon cycle.
About 83% of the world's carbon reserves are in the deep ocean and thus are presently unavailable for direct manipulation. Fossil carbon accounts for 11% of the total and as it is brought to the surface it is rapidly converted to carbon dioxide through industrial use and as fuel for automobiles. Even though atmospheric carbon makes up just slightly more than 1.5% of total global carbon, the concentration of this carbon, which has remained fairly constant over the last one thousand years, has nearly doubled in the last fifty years and shows signs of doubling again in the next couple of decades. The increased concentration of this gas serves to trap heat near the Earth's surface, leading to the melting of glaciers and the polar ice sheets, the alteration of ocean currents, and an increase in severe weather events.
Just over one percent of global carbon exists as vegetation, and just over three percent resides in the world's soils. Plants convert carbon dioxide through photosynthesis into organic material that can be consumed as food by humans and livestock. Roots and debris from plants increase the concentration of carbon in the soil, making the soil fertile, but also serving as a reservoir for carbon. Even though about fifty percent of the world's soil carbon has been lost since the development of intensive farming practices, many scientists have suggested that alternate processes such as reduced tillage, crop rotation, and returning crop land to pasture or woodland, could restore soil carbon levels to their earlier values, thus offsetting a percentage of the carbon being released through industrial and automobile emissions.
However, there is a real problem. Storing carbon in the soil is a short term fix because once original levels have been restored, there will be no way to force more carbon into the soil. At the same time, soil carbon provides the fuel for the microbes and earthworms that make the soil fertile and thus able to produce food crops. The more we try to treat the soil as a storage tank, the less we will be able to use it to feed the growing population of the world.
Reduction of dependence on fossil fuels remains the single biggest factor in resolving the problems associated with increasing concentrations of atmospheric carbon, and rather than jeopardizing yet another aspect of fragile human existence through tampering with the food supply, more effort needs to be placed into finding alternate sources of industrial energy.
