## Tuesday, September 9, 2008

### Capacity Growth

An alternative to the one percent strategy is to increase the amount of renewable resources exponentially. Throughout my discussion, I have been using the terms “renewable resources” and “capacity” interchangeably, where they are both defined as the amount of resources we are able to use that is replenished on an annual basis. Capacity is more rigorously defined as the capability of replenishing a maximum amount of resources, where the amount of renewable resources actually consumed increases until the capacity is reached; any additional consumption is supplied by non-renewable resources. If we want to supply more renewable resources (reduce the drain on non-renewable resources) then we must increase capacity; and if we want to do it fast, exponential growth is a natural way to go.

My combined population model achieves its lowest amount of error in calculating historical population (from 0 A.D.) when the capacity is zero. Because the original amount of resources is large (1.7 quadrillion pounds), even a capacity equal to the initial consumption of 300 million pounds results in a fraction of a percent increase in error. The capacity is unlikely to be larger than the amount calculated from the world ecological footprint, which I estimate to be 6.9 trillion pounds; this amount results in a 2% increase in error for 2005, which is too large to accept. The smallest the capacity could be (other than zero) is perhaps the 100 pounds per person estimated to be consumed annually in 0 A.D. (roughly the weight of a person).

When dealing with exponential growth, the starting value has a critical impact on the growth rate required to reach a final value in a given amount of time. If the world were to start increasing capacity in 2010, the rate the model predicts would be necessary to avoid population collapse varies from 9% (for a starting capacity of 300 million pounds) to 52% (with a starting capacity of 100 pounds); if the capacity were 6.9 trillion pounds, the rate would be less than half a percent. Given the stakes, I would argue for using the 52% rate if the one percent strategy was impractical (where the fraction of total consumption supplied by renewable resources is increased by 1% per year). Of course in both cases consumption must ultimately be limited to a maximum amount, which is much more likely to draw resistance than a position on the appropriate growth rate.

If we depend on Nature for renewable resources (the easiest approach to growing capacity, since the “technology” is already available), and its physical limit is the maximum capacity I mentioned, we will at best be able to support the population we had in 1980 (4.5 billion people). The rest, nearly one and a half times more, will need to come from us.