“The defining challenge of the 21st century will be to face the reality that humanity shares a common fate on a crowded planet,” asserts leading international economist Jeffrey Sachs in his new book, Common Wealth: Economics For A Crowded Planet. Sachs argues that multilateral, multisectoral cooperation is needed to address four critical global challenges: climate change, population growth, poverty, and the ineffectiveness of global institutions. By investing two to three percent of the world’s annual income in combating these problems, he contends in a piece in Slate magazine, “10 million children per year can be saved from death while stabilizing the world’s population growth, ending extreme poverty, curbing climate change, and developing alternative energy sources.”

Humanity has successfully achieved several significant collective goals, says Sachs—for instance, the almost complete eradication of polio in the last half-century, and a 90 percent decline in the prevalence of measles over the past seven years. Yet nations continue to direct massive amounts of funding toward military responses to security problems, while failing to fund far less expensive ways of preventing violent conflict.

As Sachs opines in Slate, “Today’s impoverished drylands continue to combust in a tinderbox of violence…We send armies when we should send engineers and doctors. Violence is spreading. In seven brief years, we will have squandered more in the so-called ‘war on terror’ than all the world has ever given in all of its aid to all of Africa for all time.” Sachs says his book is an attempt to galvanize world leaders to take quick and decisive collective action to address these long-term security issues.