Human population reduction is not a quick fix for environmental problems

| December 1, 2014 | Leave a Comment Download as PDF

Abstract: The inexorable demographic momentum of the global human population is rapidly eroding Earth’s life-support system. There are consequently more frequent calls to address environmental problems by advocating further reductions in human fertility. To examine how quickly this could lead to a smaller human population, we used scenario-based matrix modeling to project the global population to the year 2100. Assuming a continuation of current trends in mortality reduction, even a rapid transition to a worldwide one-child policy leads to a population similar to today’s by 2100. Even a catastrophic mass mortality event of 2 billion deaths over a hypothetical 5-y window in the mid-21st century would still yield around 8.5 billion people by 2100. In the absence of catastrophe or large fertility reductions (to fewer than two children per female worldwide), the greatest threats to ecosystems—as measured by regional projections within the 35 global Biodiversity Hotspots—indicate that Africa and South Asia will experience the greatest human pressures on future ecosystems. Humanity’s large demographic momentum means that there are no easy policy levers to change the size of the human population substantially over coming decades, short of extreme and rapid reductions in female fertility; it will take centuries, and the long-term target remains unclear. However, some reduction could be achieved by midcentury and lead to hundreds of millions fewer people to feed. More immediate results for sustainability would emerge from policies and technologies that reverse rising consumption of natural resources.

Corey J.A. Bradshaw and Barry W. Brook | PNAS | Published online October 27, 2014 | Available here

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  • A bit morbid.. you can’t impose fertility restriction to the whole world.. then again, we are overpopulating Earth…


    And here is an irresponsibly optimistic view of human activities from a piece in Nautilus .

  • This is an extremely important paper demonstrating that we are stuck with vast overpopulation for a long time, having failed to take action half a century ago when the need was first clear. As the authors note it is essential to get going now so as to both possibly save hundreds of millions from starvation in the middle of the century, and see to it that the slow decline to a sustainable population, perhaps two billion people, will begin as soon as possible. The longer we stay in overshoot, the greater the odds that civilization won’t be able to persist.

    Paul Ehrlich