The world’s population is expected to reach seven billion this month, which is “cause for profound global concern” and begs the question of “can we enjoy ‘sustainable development’ on a very crowded planet?” Jeffrey Sachs, director of the Earth Institute at Columbia University, writes in a CNN opinion piece.

“The answer has two parts, and each portends a difficult journey over several decades. The first part requires a change of technologies — in farming, energy, industry, transport and building — so that each of us on average is putting less environmental stress on the planet,” he writes, adding, “The second key to sustainable development is the stabilization of the global population” through voluntary fertility reductions. “Success at reducing high fertility rates depends on keeping girls in school, ensuring that children survive, and providing access to modern family planning and contraceptives,” he states. Not meeting these challenges “could easily carry the world to more than 10 billion people by 2100,” he concludes (10/17).