<b>A leading environmental writer looks at the unexpected effects&mdash;and possible benefits&mdash;of a shrinking, graying population</b><br> &#160;<br> Is overpopulation the most important environmental issue of our time? Already widely covered on <i>The Daily Show with Jon Stewart, </i>CNN&rsquo;s <i>Amanpour, </i>and NPR&rsquo;s <i>The Brian Lehrer Show, The Coming Population Crash</i> begs to differ: half the world&rsquo;s women are now having two children or fewer&mdash;in developing countries as well as in rich ones. Fred Pearce chronicles the troubling history of efforts to contain the demographic explosion, and then he dives into the environmental, social, and economic effects of our surprising demographic future: a shrinking, graying population; mass migrations; and, just maybe, a wiser world.