BBC NEWS | Science/Nature | Energy crisis 'will limit births'
According to some estimates, the global population may rise from its current 6.3 billion today to almost 9bn by 2050.
But Virginia Abernethy told a Seattle meeting that the loss of fossil fuels would hit world economies very hard.
"Economic hardship discourages people from marrying young and from having closely spaced children," she said.
Reproductive rates have been linked to the availability of fuel
The anthropologist and professor emerita of psychiatry from Vanderbilt University was speaking here in Washington State at the annual gathering of the American Association for the Advancement of Science.
"The availability of energy has been a major factor in population growth," said Professor Abernethy.
"In the modern context, energy use per capita affects economic activity. So a prolonged decline in energy use per capita will tend to depress the economy which, in turn, will cause a decline in the fertility rate."
Abernethy said fossil fuels had become fundamental to the continued economic growth and improving standards of living which many societies had witnessed in recent decades.
Not only does petroleum provide the fuel that powers modern vehicles and the natural gas that people use for home heating and cooking, but petroleum products are also the source for hundreds of industrial and agricultural products, including fertilisers, pesticides and plastics.
This meant that petroleum could not be easily replaced by other fuels and feed stocks, the professor argued.
"Without ample supplies of energy, we lose our agricultural capacity," she said.
"If the price of fossil fuels goes up, pesticides and fertilisers will become more expensive and that will discourage farmers from using these inputs.
"Yields will go down and the price of food will go up and that in turn is perceived as quite an economic hardship."
The limits of energy production and the limits of population are unavoidable problems that have to be faced in the near future. How quickly they are dealt with may determine how severe they become, but it seems unavoidable that there will be a price to pay for them.
Many commentators have pointed to Europe and Japan where low birth rates and aging populations have acted as a drag on the economies and national budgets. But in the long run these may be the very countries that are best postioned for the coming decline in oil and gas production--especially when combined with the increased emphasis on developing renewable resources in these countries (partially driven by their desire to meet the Kyoto limits.) When energy and food shortages are plaguing the rest of the world, these countries that are being criticized now, may emerge the least damaged.