dietz@SLB-DOLL.CSNET (Paul Dietz) (03/15/86)
Let me add my two cents worth on the "population explosion" debate: The fact that exponential growth will (ubchecked) lead to disaster is true, but not immediately relevant. The important questions are: (a) how close are we to the ultimate limits? (b) when the ultimate limits are reached, will they be approached smoothly or will a overshoot/crash occur? We are nowhere near the ultimate limits, even restricted to this planet. With the possible exception of phosphorus, all other mineral resources are either abundant or can be substituted for. Johan W. Brinck, directorate-general for Energy and Euratom Safeguards for the Commission of the European Communities, estimates the earth holds in its top 2.5 kilometers some 10**-3 to 10**-4 of its total mineral content workable at no more than twice current prices. This comes to about 10**9 tons of uranium (!), enough to supply the entire world's current energy consumption for 250,000 years if used in breeder reactors. The ultimate limit on energy consumption is set by global heating; at 50x current consumption the earth will be warmed by about 0.2 degrees C (this is from waste heat, not the greenhouse effect). Experts have argued that, in principle, world food production can be increased by a factor of ten. For this to occur desalinated water must be used; at current costs the energy for desalination would cost about $2/person/day using conventional agricultural techniques. These techniques are wasteful, however; it is possible to grow crops with 1/10 the water (as has been demonstrated in Israel), using 100 gallons to grow 2500 calories of food. Additional energy inputs (fertilizer, fuel for tractors, etc.) adds another 50%, so the energy cost is around $0.30/person/day, or $110/person/year. Will the transition to lower growth rates be smooth? It has been in the industrialized countries. Unlike a "tragedy of the commons", child rearing incurs a cost on the parents, and in western countries this has suppressed the birth rate. One might argue that eventually natural selection will favor those parents that sacrifice and have many children, but it's unclear whether this behavior is under genetic control and whether evolution would act in less than millenia. Space: current world air traffic (I think it's around 400 million person-flights per year) exceeds the world population growth rate. Assuming travel to space becomes as easy as jet travel today the world could be depopulated quickly (in decades). Space can't solve any near term population problem, but it doesn't have to. We don't *need* space resources right away either, although I'm sure profitable uses for lunar and asteroidal materials will be found.