Our work in off-shore frontier basins world-wide and in the mining industry has made us very aware of the limits to so-called non-renewable natural resources, and our environmental work has made us aware of the pressure on, and exhaustibility, of renewable natural resources.  Economists have an almost diametrically opposed view of the meaning of these terms from the public view. To an economist, when the last tree has gone, it is gone, and trees will never be available again.   However, their view of non-renewable resources is that there is always more available, albeit at a lower grade, and therefore at a higher price.
Jared Diamond, in his book “Collapse”, discussed about 17 societies around the world that had flourished to the point of exhausting some natural resource, usually a “renewable” one, and had then collapsed disastrously, with total loss of culture and great loss of life. He shows that the reason for the ultimate colapse is usually that the elite of the society failed to address the issue, even when they recognized it. These societies were mostly relatively isolated: in his last chapter he points out that the demand on resources is now global, and that all societies are inextricably linked by trade, so a major resource collapse will affect us all:  he expresses a pious hope that we will see it coming and take appropriate action.  In fact, in today’s world, many people can see huge problems on the horizon, but getting action to avert them has proved more than difficult, especially among the biggest offenders, such as the USA and China.
In my family we have direct experience of this:  the Isle of Man exhausted its forests centuries ago, and thus timber (often driftwood in the sea) became the most important asset a man could have. One of my ancestors left the planking of a rotten boat to one son in his will, and the rib timbers to another son.
Today society is totally dependent of fossil energy: without it we would not be able to make very much or transport it around, nor would we have light to read by or air-conditioning to make indoor life tolerable.  Fossil energy is intermediate in economic character between renewable and non-renewable resources: it is the fossilized remains of living (i.e. “renewable”) organisms, and there is a finite amount that is recoverable at an energy cost lower than the energy yield.  Because technology continually advances, this tipping point recedes, but it recedes at a decreasing rate, and eventually we will get reach it and find ourselves terminally short of energy.
Metallic mineral resources are a different case:  in general the lower the grade (e.g. lbs of valuable mineral per ton of ore), the more is available.  But this is not a smooth curve:  copper veins could carry 25% copper, but when we ran out of them we had to go to stratabound sedimentary copper orebodies, such as the Kupferschiefer in Europe, and the ores of the Zambian copperbelt, which run 3% copper.  The advent of plate tectonics in the late 1960s then led to a huge boom in the discovery of “porphyry coppers” because we understood where and how to look for them.  Their grade averages 1% copper.  This sort of thing is true for most metallic minerals: there are discrete types of orebody, each with its characteristic grade.  When you run out of one type, there is a big drop to the next type, and technology has to overcome the price increase that would otherwise be necessary.  In addition, mining does enormous damage to large areas of the surface, and to the groundwater below and the streams in its valleys.   As ore grade decreases, the area of land destroyed for each ton of metal recovered increases quite drastically.
Water us yet another case:  when I lived in Africa around 1970, the population f Zambia was 4 million, of Ethiopia 19 million.  Everybody lived on a stream and had access to water.   Now the population of Zambia is 17 million and Ethiopia 100 million.  Most of the rural population is forced to live very far from water, and many church groups in Austin (where I live) are raising money for drilling wells in Ethiopia, Malawi, Burundi, and so on, so that rural people do not have to spend their lives walking 10s of miles a day to the nearest river and back for water.  But most of Africa is underlain by crystalline bedrock, and the amiunt of water this can yield is very limited: if the rural population keeps increasing, the wells will have to become prohibitively deep and expensive.  In our own country, the Ogallala aquifer of the High Plains is being depleted so fast by irrigation that in some areas it is predicted to run dry within one or two decades: meanwhile, cities like San Antonio, TX, are buying up water rights a 100 miles away in order to ensure that they will have sufficient water in a few years.
All of these issues become more difficult to solve as the population of the world increases, and as it gets wealthier. There is, in my opinion, no way that the world can support 9 billion people at the standard of living we have in America or in Europe.  Already, immigration from poor countries to rich ones is causing huge political strains, and it can only get worse.
I have spent a lot of time thinking about these issues, amd trying to come up with ideas for viable solutions.


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