NEW ORLEANS—People walking around the Sheraton Hotel here are talking about population as if it were the most natural conversation in the world. The topic interests me, so I join in. As it happens, I’ve written a book on it, just published by Island Press, which I don’t shrink from mentioning. Just being here, though, reminds me that human numbers aren’t often talked about outside this hotel. If there’s a time and place for talking population this is it: the annual meeting of the Population Association of America. The association’s demographers and public health specialists gathered this year in a city that lost about half its own residents to other places after a hurricane named Katrina. Panel topics ranged from that unprecedented urban population drop (the city’s population has since rebounded to around 70 percent of its pre-Katrina size) to the intriguing idea that the HIV/AIDS epidemic has peaked globally. While PAA members presented findings and partied at the Sheraton, people in the nearby streets of the French Quarter let the good times roll, as they usually do, with nary a thought of the number of us in the city, the country or the world. But you don’t have to wander around the Big Easy to get a sense of how uneasy we are with population as an issue. Discomfort with the topic is everywhere, not least among environmentalists, who grapple daily with the ways human beings are altering the natural world and its life support systems. Who wants to reduce humanity to a number, or to see themselves as one? And population trends touch on some of the most sensitive issues in our experience: sex, race, childbearing, family size, immigration, abortion. Yet anyone paying attention to human-induced climate change or the ongoing surge in global energy and food prices must sometimes pause to think about just how many we are. The fact that a few thousand professionals meet once a year to talk about population, at least, is a good sign. And this Tuesday is Earth Day, which on its launch back in 1970 integrated population into discussions about the environment. I’ll celebrate the day by discussing my book—titled More: Population, Nature, and What Women Want along with the author of a different take on population at the Woodrow Wilson International Center for Scholars in Washington. World population has doubled since the first Earth Day. Does that mean worries about population growth were groundless, or that we’re in more peril today than in the past? And what does the future hold? From now through June, I’ll be weighing in from time to time with some thoughts on such questions on the Websites of both Island Press and the Worldwatch Institute. My book explores a few ideas that I hope will stimulate some conversation of its own, and maybe even a bit of hope for the future. I’ll welcome your comments.