The ultimate limits of most resources are difficult to assess precisely, although estimates can be made. One resource, however, has a well-defined limit: that of usable land area. The surface area of...

The ultimate limits of most resources are difficult to assess precisely, although estimates can be made. One resource, however, has a well-defined limit: that of usable land area. The surface area of the earth is 511 million square km, or 5.11
 10¹⁰
hectares (a hectare is 0.01 sq. km). Only a fraction of this is land, and only part of that land is useful—the best estimate is that 1.1
 10¹⁰
hectares of the earth’s surface is biologically productive. Industrial countries require 6 hectares of biologically productive land per head of population to support current levels of consumption. The current (2011) global population is close to 6.7 billion (6.7
 10⁹
). What conclusions can you draw from these facts?