There are plenty of people out there who would say the world has too many people in it for environmental reasons. I think that that is short-sighted because generally when people have made these arguments, they're called mouth-usian arguments after the 19th century economist Thomas Malthus. So I think you need to be a bit conditionally optimist about the earth's ability to sustain a higher population. It does depend on humanity's ability to use fewer natural resources per person, but that is possible and humanity is becoming more efficient.