In animal populations, 1 plus 1 doesn't equal 2.
There are more than 5.75 billion human beings on this planet. If we lived as hunter-gatherers, the planet might be able to support us. But we don't, and it can't. There are too many people on this planet.
Let's face it. Technology isn't going to solve this problem. It's too big. The only place that's making an attempt is China, which is desparately trying to control its population by enforcing a "one couple, one child" policy. For them it's too little, too late. And in America? Hah. We'll never deny a person's "right" to have children (unless they are queer).
The only people who have ideas that make sense are two SF authors, Larry Niven and John Varley. Niven's idea was zero population growth through "birthrights" -- the privilege of having a child. Each person has two, and it takes two birthrights (one from each parent) to have a child. There's also a worldwide lottery, which is the more interesting part. If the population shrank in a given year, the lottery was held and winners got a birthright. It's a great idea: ZPG, and, (if such a thing is possible) we also breed for luck!
John Varley's proposal is similar. Each person is issued a 75% share in a child. If two people get together, they have 150% share and can have one child. If they're interested in having more children, they have to buy another 50% share, or else they can sell their extra 50% share. The price is determined on the open market.
But the world will never adopt either of these proposals. We're going to destroy all the forests and oceans first. Bye-bye frogs.
What stuns me is that there are people who spend tens of thousands of dollars (or more) trying to have a child. This fuels an industry of research into improving human fertility. How can researchers be so irresponsible? There are too many people already! Why would we possibly want more? People are starving now, and there will be more in the future. We should be looking for ways to limit fertility. Unfortunately there's no money in that.
Theodore Sturgeon wrote the humorous story "Never Underestimate", in which a researcher accidentally caused people to only be sexually receptive for a few days a month. That's what we need: none of this perpetual fertility. What a better world this would be if people were only fertile a few days a year!
Maybe then we'd treat children like something precious, not possessions.
America is an idealist nation sometimes. We are only going to recognize that having children is not a right, it is a responsibility to the entire planet, only when the planet is too destroyed to recover. If we haven't passed that point we will very soon. And then children won't even survive.
A personal note: I don't understand the drive to have "a child of one's own". A person is a person is a person. Does it really matter if a child comes from your womb? To some people it does. What a waste. There are thousands of children in orphanages, but we all want our own little genetic clones. It's just pathetic.
Why does the U.S. government reward people who have children? Parents get tax breaks, and I don't agree with this. Children are in no way a necessity like food or shelter. They are a luxury. In this country, there is absolutely no obligation to have a child; they are a choice. Why should my taxes be higher because I choose not to have a child? Having children is a responsibility, and part of that responsibility is financial. If a parent cannot afford a new car because of the cost of raising a child, it is not my government's responsibility to pay money for that car.
It seems a much more economic notion to reward people who decide not to have children than those who do. Rather than giving yearly tax breaks to parents, why not give a much larger bonus to those who have themselves sterilized? I'd settle for a one time bonus of $10,000 to be sterilized. It would certainly cheaper for the U.S. government than the costs of schooling, law enforcement, et cetera.
Do I hear people objecting that the government shouldn't be involved in social engineering? If it shouldn't be, then what is it doing giving tax breaks to people who do have children? That's just a different form of social engineering.
The problem with this idea is that the people who would be penalized by this system would be the children themselves. To do this well, we'd have to rebuild society so that children are guaranteed the fundamentals: food and shelter. But we're not socialists, so we're not going to change anything, and we'll just go on having more children until the planet is dead.