Table 17. Carbon on the Earth
Let us put some figures to this picture. A dense, tall forested area will contain around 500 tonnes of plant material per hectare above ground. Obviously this figure will vary according to the nature of the forest, and scrubby open forests will contain less, but this gives us some sort of handle to work from. A field crop will typically hold only a few tonnes of plant material above ground when fully grown, and nothing at all outside the growing season. A pasture cover will typically have less than a tonne per hectare.
Both the field and the pasture plants will have much more water and less carbon in them than the woody plants of the forests, so as a rough figure we can assume that replacing forests by field crops or pasture reduces the carbon held to under 1% of the original figure. At the accuracy we are working at, we can assume it has all gone.
Proposition 17B
Changing land use from forest to field crop or pasture reduces the amount of ‘frozen’ carbon to negligible levels
In Table 17, mostly taken from Beckmann [1988], there is a figure for the carbon contained in the total estimated deposits of fossil fuel on the Earth. If this figure is divided by the total land area of the Earth, it gives a result which, coincidentally, is about the same as the forest — 500 tonnes per hectare. This figure takes no account of such factors as the extensive fossil fuel reserves under the sea, the many geological areas where fossil fuel deposits are lacking, or the fact that forest plant material is not all carbon, but it is another handle to use on the problem.
Proposition 17C
Fossil fuel deposits in the ground have the same magnitude of ‘frozen’ carbon per hectare as a dense forest, on an Earth-wide average
There are lessons to be learned from this comparison. First, it is much quicker, easier, and cheaper to clear forest than to extract fossil fuels from beneath the Earth, and so this forest clearance has had a much more immediate effect on the environment than burning fossil fuels. Most of our forests are already gone, but we are a still a long way from using up all our fossil fuels, in spite of widespread gloomy predictions to the contrary.
In the 1970’s we had the Oil Crisis, and I was surprised at the antagonistic response from some quarters at that time when I went on public record with a contrary-to-usual view. I pointed out that similar gloomy predictions, of the Earth running out of fossil fuels or other mineral resources within 20, 10, or five years had been made many times before in the past, dating back to the mid 1800’s. All such predictions had proved false.
In hindsight, we can see that the Oil Crisis was also a ‘manufactured’ crisis, and current worries relate to oil gluts instead of shortages. The paradoxic reality appears to be that mineral resources are not, in practice, finite; what happens when one ‘standard’ resource runs thin is that another is found to substitute for it, often one quite unappreciated at the time. For example, if there is X amount of fossil fuel deposits on Earth, there is some 2000X of other fossilized organic matter which is still untapped (Table 17).
The relevance of all this is that it is the forests, not the fossil fuels, which are both the danger and the potential salvation. Most of our forests are already gone. The position is seen to be even worse when it is remembered that Man has been clearing the world’s forests, intentionally and accidentally, not for one or two centuries but for tens of thousands of years. Primitive man changed whole landscapes, whole climates. Even so, we can still restore the health of the Earth, with the use of ecologies and economies in which tree crops are no longer the forgotten Third Component of agricultural land use.
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