Many people seem to feel it's a disaster now there are seven billion people on the planet, but there are several arguments that can be used against this view. The most important one may be, "What a miserable, grumpy, cynical, snobbish, wretched way to look at the world. I bet you're fun when a friend has a baby. Do you send them a card saying 'With deepest regrets' and if someone's killed in a car crash send their family a balloon with a picture of a champagne bottle on the side and 'Congratulations! It's a corpse!' in bright purple letters?"
These people must wish the news would end with Fiona Bruce saying, "And finally, on a lighter note, an earthquake in Indonesia killed 50,000 people today, so at last that's knocked a bit of a hole in the world population. Good night." Presumably when they were at school they'd shout at the start of every history lesson "Can we do the plague again please sir? Oh PLEASE".
The idea that an increase in population is inevitably a calamity doesn't make economic sense either. Because 5,000 years ago there were probably only around 100 million people on the planet, so if it is true they must have been rolling in it, buying second mud huts as holiday homes, and making hip-hop videos covered in wolf's teeth bracelets. Twenty thousand years earlier there were even fewer people, so they must have been disgracefully decadent, which explains why the Neanderthals died out, as the only species to have partied themselves to extinction.
The mistake the pessimists make is in seeing each of us solely as consumers, while forgetting that most of us can also produce. So the number that can be allowed here safely remains static, as if the planet's a nightclub, needing bouncers at maternity wards going, "Hang on. Wait. Stop pushing. Right, there's been four deaths in Argentina so I can let four of you in but NO MORE."
One way to judge whether a rising population causes shortages is to look at where the worst poverty is. Manhattan is one of the most densely populated areas of the world, so I would imagine the people must all be wafer thin, especially when compared to sparse areas such as lucky Somalia, where they must have so much spare food they spend all day throwing it at each other in food fights.
Maybe environmental problems start when some people consume more than they produce. And that could be people such as Russian football club-owning billionaires with 500 million pound yachts, or it might be those Africans, who have such little understanding of economics they have the cheek to be cheerful if they manage to stay alive.