There are already 6.8 billion people living on this crowded planet and the figure is expected to rise to 9 billion by 2050. How can we expect to reduce global carbon emissions
by 50 per cent or more if populations continue to grow exponentially?
Family planning is often regarded as taboo by environmentalists, but
many are now coming round to the view that curbing population growth will be crucial to combat climate change.
The Optimum Population Trust (patron, David Attenborough) runs a campaign urging parents to "Stop At Two". Gordon Brown's green adviser Jonathon Porritt and Science Museum director Chris Rapley have also spoken of the environmental importance of tackling population growth.
Ed Miliband, the UK's secretary of state for energy and climate change, addressed the issue recently at a town hall meeting in Oxford.
"There's no question that population growth is part of the reason why
we have growth in carbon emissions ... but I'm not sure that there's an
easy or necessarily desirable solution once you've stated that fact."
are plenty of reasons why reducing birth rates might not be desirable.
No country wants to end up with a situation in which the workforce is too small to support the elderly – as Japan and China are experiencing.
of the projected global population increase will happen in the
developing world, but the impact of each extra person on the climate is
less in poor countries because emissions per capita are lower. Can we
quantify the extra emissions that result from each child born?
Statisticians at Oregon State University have done just that. Paul Murtaugh and Michael Schlax calculated that every child in the US adds 9,441 tonnes to each parent's carbon footprint.
This is assuming that emissions per capita continue at today's levels.
Compare that with 1,384 tonnes of carbon dioxide for each child in
China, or 56 tonnes in Bangladesh.
To arrive at their estimates,
published in the journal Global Environmental Change, Murtaugh and
Schlax started with the basic premise that a person is responsible for
the carbon emissions of their descendants, weighted by their
relatedness. So a mother and father are each apportioned half of their
child's emissions, a quarter of each grandchild's emissions and so on.
The researchers used UN projections of fertility to simulate 10,000
family lineages in each of the world's 11 most populous countries, and
estimated what the "carbon legacy" of an individual would be in
different scenarios of future emissions levels.
are unaware of the power of exponential population growth," Murtaugh
said. "Future growth amplifies the consequences of people's
reproductive choices today, the same way that compound interest
amplifies a bank balance."
The perceived right to start a family
is a sensitive topic, so it's hardly surprising that some have reacted
badly to Murtaugh's research. "However new-sounding the language about 'carbon footprints' may be, what we have here is the same old Malthusian view of people breeding themselves to destruction," wrote William McGurn, a former speechwriter for George W. Bush, in an opinion article in the Wall Street Journal. The Baltimore Reporter went further, calling the authors "reproduction Nazis".
to say, Murtaugh and Schlax are not advocating eugenics. They "simply
want to make people aware of the environmental consequences of their
So now that you know that becoming a
parent could lead to a legacy of 262 times more carbon emissions than
failing to convert to energy-saving light bulbs, are you still keen to
start a family?