Someone once said that the only sincere act of an extreme environmentalist is to commit suicide. This relates to my hereby proposed Butler's Law of Environmental Degradation, as follows:
People = Pollution
Even the most environmentally pristine of us generates a tremendous amount of pollution, just by being alive. The amount of pollution generated in order to feed, clothe, shelter, and transport each of us is enormous. In this context, agonizing over the impact (for example) between a synthetic and down sleeping bag might make one feel better, but it has virtually zero practical environmental impact on a planet with over 6 billion (and growing) polluting people. It's not even a drop in the bucket.
This will make some people uncomfortable or even angry, but I believe that the most important long-term environmental decision the average person can make is how many children to have. I'd argue that the decision to have an additional child will, for the average person, have a larger long-term impact on the environment than all the other environmental decisions that person makes put together.
There's an analogy with compound interest. The number of kids each person has on average is like an interest rate, and the average age at which people have children is like the frequency of compounding. If everyone has 4 kids starting at the age of 20, the population (and pollution) explodes. But if everyone has 2 kids starting at the age of 30, the population stabilizes, or even declines. Waiting significantly longer to have kids reduces the number of generations of a given family who are alive at any particular time, which reduces population and therefore pollution. That's just the inarguable way the math works.
A more subtle point is that, in contrast with many environmental decisions, a decision to have fewer children causes a permanent environmental improvement lasting after one's death, because you've created fewer polluting descendants for all time.
The thing is, I love kids! It makes me uncomfortable as well to say all this. But it's reality.
So by all means, make a good effort to reduce your environmental impact via the usual methods. But don't kid yourself that you're having a large effect in the overall scheme of things. To have a much bigger impact, have fewer kids, have them later in life, or both.
If you're inclined to get political about this, focus on trying to change government policies which encourage population growth. These policies exist all over the world in one form or another. The most obvious example in the US is the income tax exemption per child, but there are many other examples as well. At the very least, these policies should be reduced or eliminated to help reduce population and pollution growth.
And now, back to our regularly scheduled programming. :-)