OP-ED...The end of growth is improbable

     World population:  The end of growth is improbable

    The global population may not stabilize at a level of 10 billion, as projections by the United Nations suggest.

   UN projections suggesting that the world population will stop growing after reaching a level of 10 billion people at the end of this century are improbable.

    While there could be stagnation over the short term, even small fluctuations in the energy or food supply could cause the population size to deviate from the 10-billion mark, and enter another period of strong growth.

   This finding comes from model calculations performed by Oskar Burger at the Max Planck Institute for Demographic Research (MPIDR) in Rostock, Germany, together with John DeLong from Yale University in New Haven, USA, and Marcus Hamilton from the Santa Fe Institute in Santa Fe, New Mexico.

    "The upper limit suggested by the United Nations hardly represents a stable equilibrium," Oskar Burger said.

   The results of the team's model have now been published in the science magazine "Frontiers in Ecology and the Environment".

   The model is based on the observation that population growth strongly depends on per capita energy use; if more energy is available, economic development will continue, which will in turn put pressure on birth rates.

   If birth rates are sufficiently low throughout the world, the global population will stop growing.

   Burger's model is thus at variance with the projections of the United Nations, which simply extrapolates a trend toward declining numbers of births observed over the past several decades.

   Zero growth is possible, but it will not last.

   "At a level of 10 billion people, zero growth is indeed within reach," Oskar Burger said. "But the population  size will remain at this level only if sufficient energy per capita remains constantly available."

   But that can hardly be expected.  "Since 1960, the population has been growing faster than the amount of usable energy worldwide,"Burger said.

   Thus, on average, the amount of energy available per person has been decreasing, and this trend is continuing.

   "In the last 50 years the world population has actually moved farther away from reaching a stable equilibrium," the MPIDR researcher said.

    If zero population growth does in fact  occur at a lavel of 10 billion people, but there is an insufficient supply of energy, it could only take a very small change in the resources or in the behavior of societies to trigger a deviation from this trend, which could gain momentum very quickly.

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