The Earth has been around about 5 billion years, life about 4 billion.
Half a billion years for animals, 200 billion for mammals.
200,000 years of humans.
For the first 192,000 years or so, the human population was under 10 million people world wide.
Increasing 10 fold took 6000 more years.
We rocketed from 100 million to a billion in just over 2000 years.
The next billion only took 120 years.
And then 30.
And since the 1950s, we have added a billion people every 13 years or so.

We are at around 6.75 billion people now.

http://upload.wikimedia.org/wikipedia/commons/b/b7/Population_curve.svg

Its estimated that it will hit 9 billion in about another 30 years.
That new 2 and a quarter billion people will be our children.

We
like to point to the 3rd world, to Asia and Africa, but in the measure
that matters, the US is by far the most overpopulated country in the
world, as well as one of the fastest growing.

Population is only an issue because of the finite resources the
Earth can provide.  If we had unlimited resources there wouldn’t be any
reason not to keep increasing indefinitely.

If everyone used the
same amount of water, land, and energy, and caused the same amount of
pollution as the average person in the third world, we would all be ok
for a long time to come.  Due to lack of ability, what we call poverty,
people in the third world tend to use less than their share of world
resources.

The average person in the first world uses 5 times more than the overall world average.
The
average American uses 20 times more.  Each of us uses about 20 times
more water, 20 times more fuel and electricity, 20 times as much land
to produce our food, produces 20 times more waste and pollution. 

Which means that in the big picture, each of us counts for 20 people.

So
our 305 million population may as well be 6.1 billion, far more than
China’s 1.3 billion.  They would have to increase some combination of
actual population and consumption per person by far before we could
legitimately point the finger at them.

It also means that each child we have counts as 20 people, turning
our fertility rate of 2.1 (already above the replacement rate of 2)
into the equivalent of 42 per woman, 6 times higher than the highest
rate of any third world country – and almost 17 times higher than the world average.

In the US alone there are 200,000 children waiting to be adopted.

It is one of the most basic and universal desires is to
reproduce.  How could it be any other way? Because if that drive
weren’t passed along genetic lines, our ancestors wouldn’t have
bothered, and we wouldn’t be here to think about it.

There has been a widespread assumption that because it is natural
and universal that therefor it should be considered a human right.

Our
modern world does not resemble the savanna we evolved on.  We also have
biological instincts to eat whenever food is available in case it isn’t
tomorrow – and the result is rampant obesity – and a good number of us
making the conscious choice to go against instinct and manipulate
ourselves in ways that take into consideration the reality of our
world.  Violence is natural and universal, but we agree as a society
that the costs are not acceptable and make the conscious decision to
repress it, both as individuals and as communities.

Because, we can do that, we can think, and make choices.

To make wine or beer, you start with grape juice or grains and add microorganisms.
For
them it is an incredible feast!  Sugar and carbs as far as the eye can
see, no predators, no competition, perfect weather.  So of course they
have a really good time, girl fungus meets boy fungus, there’s plenty
to feed the babies and things just couldn’t be better.  And then after
a while they literally die from drowning in their own waste products as
the population gets completely out of control.

(And then we drink that waste product, but that’s another topic entirely)

Human beings, in theory, are a lot more intelligent than yeast.  They
don’t even have brains.  As individuals we can choose not to have
children.  But as a whole, an outside observer would not see much
difference between the species.  As a whole, we continue to breed at a
rate related only to the resources available today, with little or no
regard to how sustainable those resources are.

A great many people – including liberals and environmentalists and
those who are childless by choice – become indignant when this topic is
brought up.  Reproduction is considered by many to be a fundamental
(God-given?) right, and suggesting otherwise brings to mind eugenics
programs, or the murder of female infants when China first instituted
its one-family/one-child program when sons were the only form of social
security the society had.  Those are not inevitable outcomes. 

As a specie all societies choose to discourage some of our natural
instincts in such a way that slight personal restrictions result in a
far happier society over all.  It may be perfectly natural for me to
want to punch some annoying person right in the face, but the
government isn’t going to give me a tax break for doing it.
Just the same, it is only natural that I want to have my own kids,
related to me by DNA, but if it is going to end up making life that
much more difficult for all of the people who are already here, perhaps
a tax penalty is more appropriate than a credit.

Average cost for fertility treatment is $12,000, and 12% of US couples
seek it.  In about 1/2 the states this is covered by insurance.
Given the 200,000 existing children who need homes, I find this
immoral.  Think what medical services could be provided to people who
are already here with that $4 billion.

Governments could encourage this simply by removing tax breaks for kids. 
I don’t actually think that is going to happen.

But you and I can still choose on our own to act, even if everyone else
isn’t likely to fall in line.  Its been calculated time and again that
simply having a baby has greater impact than all the imported GMO
processed food and single-person commutes in SUVs could ever hope to
have.  From an ecological standpoint, it would be better to drive a
hummer and eat at Mickey Ds but adopt your child then to live the hippy
lifestyle in a solar powered yurt with a grey-water garden and create 3
brand new babies of your own.

And now we get to the real crux of the matter.
Being aware of this, just how much personal sacrifice are we willing to
make?  I want the experience of creating a child.  I also to avoid
being an amoral moral and not a hypocrite.  (A moral hypercrite? Yes. 
I aspire to be a hypercrite someday.) 
Like most people, I have developed a defensive rationalization to allow
me to not feel guilty about doing what I wanted to all along, even
though I really know better.

The way I see it, I personally can’t be expected to be held responsible
for or make up for the excessive consumption of everyone else around
me.  I couldn’t if I wanted to.  I personally have a sustainable
ecological footprint (i.e. if everyone on the planet used the same
level of resources as me, we’d all be set indefinitely).  If me and my
hypothetical future partner have 2 kids, once we die, overall, the
population hasn’t gone up.  If we have just one, its gone down by one. 
That seems like a decent compromise to me.  I’d like to have one, and
adopt one.  (As a bonus, I can choose to have one of each gender, and
more precisely choose the age spread).

Many people object to ideas around population control as an emotional
response to implied guilt about already having children, and feeling
defensive about kids that are already here.  A potential person has
nothing in common with a real human being who is actually here. 
Acknowledging that resources have a finite rate of renewal is not a
personal attack on you. No one is saying your child isn’t wonderful or that you made any
“wrong” choices. All I am saying is, however many blessings you have,
stop now.

Similarly some people in these discussions suggest that if any one who
advocates population control should kill themselves if they really mean
it.  This equates the mere idea of a person, a hypothetical, potential
person, with an actual specific person who is here right now, thinking
and breathing and feeling.  We aren’t talking about abortion here.  Not
having a kid is not killing by any definition.  Any discussion about
who a person who does not exist might possibly become is equally
ridiculous.  That kid who could someday be is no more likely to become
the next president than it is to be a serial killer who enjoys
torturing victims. 

Bottom line is, having less children today will be much less painful
than wars of dwindling resources some number of decades in the future.