Environmental Management: Principles and practice

Environmental limits
Von Liebig’s Law of the Minimum states that whichever resource or factor necessary
for survival is in short supply is the critical or limiting one which restricts population
growth of a species—for example, lack of water, space, nutrients, or harsh climate,
noise, recurrent fires, a predator, disease, etc. A population of organisms will tend to
grow until it encounters a resource limit or limiting factor. The outcome may then be
gradual or sudden, limited or catastrophic, or cyclic boom and bust but whatever
course is taken there will be a cessation of growth. Solar energy drives most of
Earth’s ecosystems: few are not ultimately dependent on sunlight. Exceptions include
deep ocean hydrothermal vent communities and bacteria deep underground (Cann
and Walker, 1993). Photosynthesis is thus a major parameter, and few of the world’s
agricultural strategies function at anything like potential maximum efficiency, so
improvement of food and commodity production without further expansion of
farmland should be possible.
There has been much debate as to what the maximum global human
population could be without causing serious disruption of the Earth’s life-support
systems. Miller (1991:138) suggested that, with technology and foreseeable
economic development, global population might reach 10 or even 30 billion
(thousand millions). The global population is already more than halfway towards
the lower of those two estimates so humanity would be advised to treat the problem
with urgency. Caution is necessary when dealing with estimates of the population
the Earth might support as they are often speculative. It may be possible to produce
40 tonnes of food per person for the 1990 global population, but will there be
investment, environmental and social conditions allowing that production to be
maintained in the future, let alone be expanded? Meadows et al. (1992) have
argued that the limits have already been exceeded, but that there is still hope of
human survival and ultimately stabilization at a level offering reasonable quality
of life.