In an era of changing climate and sinking economies, Malthusian limits to growth are back—and squeezing us painfully. Whereas more people once meant more ingenuity, more talent and more innovation, today it just seems to mean less for each. Less water for every cattle herder in the Horn of Africa. (The United Nations projects there will be more than four billion people living in nations defined as water-scarce or water-stressed by 2050, up from half a billion in 1995.) Less land for every farmer already tilling slopes so steep they risk killing themselves by falling off their fields. (At a bit less than six tenths of an acre, global per capita cropland today is little more than half of what it was in 1961, and more than 900 million people are hungry.) Less capacity in the atmosphere to accept the heat-trapping gases that could fry the planet for centuries to come. Scarcer and higher-priced energy and food. And if the world’s economy does not bounce back to its glory days, less credit and fewer jobs.

It’s not surprising that this kind of predicament brings back an old sore topic: human population and whether to do anything about it. Let’s concede up front that nothing short of a catastrophic population crash (think of the film Children of Men, set in a world without children) would make much difference to climate change, water scarcity or land shortages over the next decade or so. There are 6.8 billion of us today, and more are on the way. To make a dent in these problems in the short term without throwing anyone overboard, we will need to radically reduce individuals’ footprint on the environment through improvements in technology and possibly wrenching changes in lifestyle.

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