Bad ideas have a habit of sticking around. More than two hundred years ago, Thomas Malthus predicted that population growth would inevitably outstrip the pace of food production, leading to calamity. Since then, his model has been used in all manner of heinous ways, first to justify slashing aid to the poor, and later by eugenicists in the early twentieth century.

Malthus’s theory is still with us today. Only this time it’s some segments of the environmental movement who propose illiberal methods to prevent a Malthusian catastrophe.

Columnist Dan Savage made waves a few years back after half-jokingly suggesting that “abortion should be mandatory for about thirty years,” and that population control would need to be instituted. Before that, British journalist Alex Renton argued that governments in the developed world should offer incentives and penalties to induce families to have less children, while hinting that, down the line, it may have to happen “the hard way.” Canadian reporter Diane Francis posited that a “planetary law, such as China’s one-child policy” was necessary to prevent global warming, and that “birth restriction is smart policy.”