That figurative pachyderm is human population growth, an issue that may overwhelm any efforts by developed nations to reduce their greenhouse gas emissions. Indeed, if the emission rate for every person on earth could be reduced by one third, that increase in population would balance the emission reduction, and atmospheric greenhouse gas concentrations would continue to rise at the present rate. One important consideration overlooked by those in developed nations who object to the idea of limits on population is that without a decrease in worldwide population growth, all nations will become overpopulated, as desperate migrants from impoverished, crowded regions seek work in developed nations.