Reading Andrew Revkin's blog the other day, I got uncomfortable. Granted, for an environmentalist, this isn't a new feeling. When you're attempting to safeguard the earth against collapsing fish stocks, rising sea temperatures, a changing climate and disappearing forests, managing discomfort becomes your stock and trade.

But this was about population. Even amongst friends, this can be an uneasy conversation.

At a time when environmentalism is no longer the hobby of the radical few, but is emerging as a mainstream consideration, the question of population remains largely taboo. And not without good reason.

There is nothing more personal, nothing we guard more, than our children. It's where our sense of an essential human right -- to bear and rear our own -- meets environmental responsibility head on. And it's where our sense of sacrifice feels almost too great to bear.

But as an environmentlist, the proposition of booming global populations is daunting. A recent NY Times Op/Ed by Jared Diamond that shifted the debate to consumption levels was particularly disconcerting. In it he said, "Some optimists claim that we could support a world with nine billion people. But I haven't met anyone crazy enough to claim that we could support 72 billion."

For a long time now, I've looked forward to being a father. At 25, I am by no means ready -- but the decision of how many I should have nags me. I try to balance an interest in building a family with a sense of global responsibility. And so, as with any question that nags me, I've been reaching out and talking to people. The responses have clustered in these categories.

The miracle seekers. When asked, a very close family friend said, "I'd hate for you to deprive yourself. Seeing your own self -- your own DNA -- in this little is completely miraculous. It's one of the miracles of life." It's a sense of a fundamental human right -- of an undeniable experience we should all share.

The doomsayers. Some of my friends are uncertain as to how many kids they want to have simply because they're not certain whether there will be a world left for this kids to live in. If the parent's essential goal is to provide the conditions for a better life for your children, what become of parenting if these conditions are out of your control? It reduces parenting to a basic process of reproduction.

The adopters. Still others look to adoption as the solution. Some of my friends raise this point repeatedly in discussions of family plans. And why not? It just makes sense.

The answer is that there is no answer -- it's a deeply personal question. I fall somewhere between these poles, convinced that our world will be environmentally degraded, but eager for the opportunity to raise my own.

Is that selfish? I hope not.