One obvious need is to cut individual consumption rates – somehow. But until the world's population stops growing, there will be no end to the consumption squeeze. With the 9 billion people demographers project by 2050, even a global average lifestyle such as South Africa's could be unsustainable. Acting on both population and individual consumption consistently and simultaneously is the key to long-term environmental sustainability. For the sake of the poor, let alone the rest of the world, we'd be better off if population ended its growth soon and moved gradually to a level lower than today's.
For most of the public, slowing population means "population control," as in China. But the concept of "control" is, for good reason, anathema to most people. As it happens, it's actually more effective to address population based on our right to decide for ourselves if and when to have children. The basis for action is something that also makes sense for other reasons: Make unintended childbirth as rare as possible. The benefits ripple out from women's lives in particular to all of humanity and to nature.
The idea is hardly new. At a United Nations Conference in Cairo in 1994, almost all the world's nations agreed to reject population control and instead help every woman bear a child in good health when she wants one.