Human population and a sustainable future

Human population and a sustainable future

Population reduction will likely benefit the planet in the long-term, but can it address our most pressing environmental concerns?

Original Paper:
Bradshaw CJA and Brook BW. "Human population reduction is not a quick fix for environmental problems." Proceedings of the National Academy of Sciences. Online. DOI: http://dx.doi.org/10.1073/pnas.1410465111

Over the last century our population has more than quadrupled, with Earth's population reaching an estimated 7 billion people in October 2011. This rise has been so rapid, that an astonishing 14 percent of all humans who have ever lived are alive today. While the rate of growth is slowing, our population will continue to rise; recent projections pin the global population between 9.6 and 12.3 billion by the end of the century.
 
As we harness more of the planet's resources to support our increasing numbers, we continue to see major environmental changes. An increasing population challenges our ability both to live sustainably as a species and mitigate human-driven climate change. Given the challenges aggravated by population growth, it is logical to assume that reducing the population size could help address these environmental concerns.
 
A recent study in the Proceedings of the National Academy of Sciences looked at a number of different scenarios to gauge how long it might take the human population to plateau and then decline. The Australian researchers then used these projections to discuss how reductions in population might affect worldwide environmental issues.
 
Population patterns change over long time scales, due to what is called demographic momentum. The findings of the study indicate that the existing demographic momentum of a still growing population will outweigh any short-term attempts at managing population size. Therefore, these management attempts should not be thought of as "quick fixes" in addressing humanity's environmental impact.
 
Many of the findings highlight the strength of this demographic momentum. For example, the study found that if every unplanned pregnancy were avoided worldwide due to reproductive education, family planning, and cultural shifts, population would peak at 8.39 billion in 2050 and then fall to 7.3 billion by 2100, a level slightly higher than today. The study also found that implementing contentious population control measures such as a worldwide one-child policy, results in a population that wouldn't fall back to present-day size until the end of the century. Another scenario looked at a hypothetical catastrophic mortality event equal to the number of deaths from the First World War, the Second World War, and the 1918 Spanish flu epidemic combined. This event barely altered the long-term population projection.
 
The study does not discount efforts already taking place. Effective family planning and reproductive education can lower population by hundreds of millions compared to baseline projections in the middle of the century. This can lead to important environmental and societal benefits for future generations, but is unlikely to impact the lives of those living today or in the near future, nor will it quickly stem environmental impacts.
 
Regardless of future population patterns, humans can make more immediate and positive environmental change by working to reduce our collective footprint. International climate change and greenhouse gas emission agreements can have large-scale impacts. Innovative local and regional planning can help conserve biodiversity hotspots, reduce waste, and ultimately lessen negative impacts. Effective interventions will take technological and social innovations, as well as substantial effort, but have the potential to improve sustainability in the near term. These interventions can be coupled with long-term population planning.

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