New multi-scenario¹ modelling of world human population has concluded that even stringent² fertility restrictions³ or a catastrophic mass mortality would not bring about large enough change this century to solve issues of global sustainability. Published in the Proceedings⁴ of the National Academy of Sciences of the USA, ecologists Professor Corey Bradshaw and Professor Barry Brook⁵ from the University of Adelaide's Environment Institute say that the "virtually locked-in" population growth means the world must focus on policies and technologies that reverse rising consumption of natural resources and enhance recycling, for more immediate⁶ sustainability gains.

 

Fertility reduction efforts, however, through increased family-planning assistance and education, should still be pursued, as this will lead to hundreds of millions fewer people to feed by mid-century.

 

"Global population has risen so fast over the past century that roughly 14% of all the human beings that have ever existed are still alive today -- that's a sobering statistic," says Professor Bradshaw, Director of Ecological⁷ Modelling in the Environment Institute and School of Earth and Environmental Sciences. "This is considered unsustainable for a range of reasons, not least being able to feed everyone as well as the impact on the climate and environment.

 

"We examined various scenarios⁸ for global human population change to the year 2100 by adjusting fertility and mortality rates to determine the plausible⁹ range of population sizes at the end of this century.

 

"Even a world-wide one-child policy like China's, implemented¹⁰ over the coming century, or catastrophic mortality events like global conflict or a disease pandemic, would still likely result in 5-10 billion people by 2100."

 

The researchers constructed nine different scenarios for continuing population ranging from "business as usual" through various fertility reductions, to highly unlikely broad-scale catastrophes¹¹ resulting in billions of deaths.

 

"We were surprised that a five-year WWIII scenario mimicking¹² the same proportion of people killed in the First and Second World Wars combined, barely registered a blip on the human population trajectory¹³ this century," says Professor Barry Brook, Chair of Climate Change at the Environment Institute for this study, and now Professor of Environmental Sustainability at the University of Tasmania.

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