Thomas Robert Malthus : The opinions expressed in this commentary are solely those of Jeffrey Sachs . earth 's population will hit 7 mid-century ; milestone , huge challenge . He says with Earth 's resources already stretched thin , rapid growth is cause for concern . He asks : How do we increase opportunities for all , leave a usable planet for future ? Sachs : Vital to switch to sustainable technologies , cut fertility rates .
Thomas Robert Malthus : earth 's population will hit 7 mid-century ; milestone , huge challenge . He says with Earth 's resources already stretched thin , rapid growth is cause for concern . He asks : How do we increase opportunities for all , leave a usable planet for future ? Sachs : Vital to switch to sustainable technologies , cut fertility rates .