There are carbon calculators galore on the web — including The Nature Conservancy’s very own. These calculators allow you to figure out how your activities and lifestyle contribute to the carbon emissions that are responsible for the climate disruption the world now faces.

Rarely, however, does one see any discussion of what population growth means for our emissions challenge. This is why I took notice of a recently published analysis in the journal Global Environmental Change that combines data on per capita emissions with national patterns of birth and death to calculate the total emissions cost of deciding to have a child.

The scientists get their results via an elegant application of lineage analysis — a branch of mathematics that combines probability theory with demography. The mathematics is only a tool. It is the results that are compelling.

The average lifetime emissions of people living in the United States is 1,644 tons of carbon. If you live in the United States and have a child, the average carbon legacy of that child will be 9,441 tons — that is how much extra carbon you are responsible for because you had that child, and it includes all of the carbon emitted by that child and his or her descendants before that lineage dies out given current birth and death rates in the United States.

To put this another way, suppose you are committed to doing something about climate change and want to do everything possible to reduce emissions. Now assume you do all of the sorts of things we are told to do to cut down, and you do them for your entire life. Specifically:

  • You switch from a car that gets 20 mpg to one that gets 30 mpg, and you reduce the miles driven per week from 231 to 155.
  • And you replace single-glazed windows with energy efficient double-paned windows in your home.
  • And you replace 10 75-watt light bulbs with 10 25-watt energy efficient light bulbs.
  • And you replace your old refrigerator with a top-of-the-line new energy-efficient refrigerator.
  • And you religiously recycle all newspaper, glass, plastic, and aluminum and steel cans.

If you did all the above, you would be an eco-hero — and over your lifetime, you would reduce your emissions by 388 metric tons. Not bad.

Now suppose you decided to reduce by one the number of children you intend to have. You would save 9,441 metric tons of carbon emissions.

Now I have kids, and I am no eco-hero by any measure. In fact I am likely an eco-disaster. And I realize regulating population growth is not a viable option.

But, especially in high-consumption societies like the United States, even the smallest reductions in birthrates can make a huge difference to carbon scenarios. In contrast, deciding to NOT have a child in Bangladesh saves 56 metric tons of carbon, which is roughly what you get for recycling all of your newspapers and bottles and cans and switching those 10 light bulbs from 75W to 25W energy efficient light bulbs.

So let’s not pick on Bangladesh for its high population growth rate, when our own reproductive decisions have far greater environmental impacts.

(Image: Djurslands Motorway, Denmark. Credit: snorri7 under a Creative Commons license.)

If you believe in the work we’re doing, please lend a hand.


  1. I unequivocally disagree. Conservation is “for the future”… and if there are no children, there is no future.

  2. CO2 is good. The earth is cooling, and it will continue to cool. Solar activity, which drives global temperature, was at “grand maximum” levels from1 940-2000. THAT is what caused late 20th century warming, not CO2. From “grand maximum” levels, solar activity (now in an extended lull) had nowhere to go but down. It is too bad that CO2 does not have a significant warming effect, because we will need it. But it still is plant food, so it does SOME good. If children produce CO2, that adds to their value, but very little compared to their intrinsic value.

  3. I like the article, but wonder if it’s perhaps a little short-sighted.

    When you consider that the majority of the US is likely having children with no thought at all to the environmental consequences and may be raising them to NOT bother to think about their environmental actions, I think that people that are compassionate and considerate enough to be having this internal debate will probably have thoughtful, compassionate and considerate children. Children that may pass those qualities onto their own children.

    Smart, thoughtful people not having children because of environmental guilt might be like reverse natural selection. =) That said, I’m not advocating having 6+ children or anything.

    Also, I think an option that’s often left out of this debate is adoption. There are millions of children already in this world that need families. You don’t have to give birth to a child in order to be a parent. You can be an eco-SUPERhero and still be a parent when you adopt.

  4. Huge advocate of reducing the # of children we have, but I can’t help but instinctually agree with Leila. In as much as conscientiousness is heritable, removing ourselves from the gene pool isn’t necessarily the best idea, no?

  5. I can’t tell if this is a joke or a serious post. As a joke, it’s too long-winded to be funny. As a serious post, it’s too intellectually dishonest to be useful. Let’s see: by your numbers, the average carbon legacy of one child equals about 5 generations of offspring. So you’re looking at roughly 125-150 years down the road. Here’s the problem: we aren’t going to have fossil fuels in 125-150 years, not in significant numbers at least. We’ll have had to adapt by then, one way or another. So the energy usage of a kid in 2100 will be a completely different thing. Yes, we’ll still release carbon into the atmosphere, but in a closed cycle, not today’s open-ended fossil-fuel-caused upward spiral. Second, is it responsible to suggest reducing population in a technologically advanced country whose schools can best educate tomorrow’s environmental leaders, and whose scientific resources far outstrip Bangladesh’s? Third, as Bangladesh’s population is growing far faster than the U.S.’s, the pressures they’re producing on food resources means far more environmental degradation–in a part of the world with many already endangered/threatened animals and ecosystems–than the fairly stable & sustainable current U.S. birthrate. And their methods of cultivation & land management are far less advanced & far more wasteful than ours in many regards. The list goes on. Listen, there are many good reasons to think about population stabilization, carbon emission, all that, without distorting figures and creating shock-value “facts” that dissolve under even cursory inspection. It doesn’t help.

    1. I double check the numbers and they are in fact correct.

      You also mentioned ,”So the energy usage of a kid in 2100 will be a completely different thing.” I think you missed the point ,which is that not about saving energy. The point is having one child will reduce one’s carbon legacy by 9441 metric tons. Which is significant when applied to a global scale.

      Population growth of the human race has gotten out of hand, resources are being depleted at a rate faster than the earth can produce and yes in the future we will have to rely on nuclear energy, because like you said by 2100 we will have depleted earths petroleum supply.

      So what… we can find alternative sources of energy. But what happens when there is no room left in this world and all it’s sources are depleted? Do we expand to another planet?

      At the rate we are going technology isn’t advanced enough for expansion to other planet. We see that in the near future the human race will have devastated and exhausted Earth.

      Why wait to do something about it. Strike the problem at it’s source. Cure the disease. Not the symptoms. Restrict population growth by having less children.

  6. I believe people need to be more responsible when deciding to have children, but it has very little to do with carbon counts.
    If the Industrialized world (yes, there is more than the US to account for this) wants to truly make an environmental impact, let’s forget about this life of indulgence we’ve created for ourself and work together on fixing things. Quite honestly, there enough people in North America not wanting to have kids, that this should offset the need for people to have 2, 3 or 6.

  7. I am chocked by your text and largely disagree. It carries a fully malthusian and negative view of human society. As I try to be both an environmentally conscious citizen and a humanist, I cannot accept this view of the “cost of a child”. This is not acceptable as it negates the possibility that this child can later act as a very positive force to defend the planet (not just the atmosphere, but also habitats which is may be a bigger issue). I do not buy your figures and believe that more serious changes in habits, in addition to technological improvements, could lead to much larger reductions in per-capita emissions of CO2. Just to get an idea, could you remember that an average citizen in Europe emits almost half of what a USA citizen does ? And we all could do way better! Please stay positive regarding to humanity.

  8. I am really glad to know that calculations like this are being done and to see this article; it provides a nice response to a world that continues to insist that parenthood is the ultimate selfless act. While I agree that parenthood requires sacrifices, there are many negative impacts associated with increasing the number of people – especially Westerners – in the world. These impacts include, among others, the long carbon trail described in this article, and it’s important to be aware of them when making personal decisions about having children, as well as when making larger government policy decisions.

    Many of the respondents so far seem to have misunderstood the point, though. The author was not saying that all human reproduction should stop. Instead, he was merely saying that those of us concerned about the planet should know the environmental impact of producing a child. He fully acknowledges the urge that life has to produce more life, but is just arguing for a little moderation – and saying that a little moderation (i.e. having one less child) can have a much bigger impact than one might expect. And, in turn, that that moderation might leave the world a better place for any children that you do decide to have, in addition to leaving it better for other life on the planet.

    I also disagree with the idea that the only way to create an environmentally conscientious person is to give birth to them. A better strategy might be to work with the people who are already here – adopt the ones who need adopting, if you feel the urge to have children, and teach them your values; teach other people’s children; teach other adults. It can take surprisingly little effort to change a person’s views on environmental issues – there is a huge void of information out there, and a huge hunger for it. I appreciate this article for helping to fill that void.

  9. I’m not having kids because, well, I don’t want kids. Helping the environment is just a side benefit.

  10. Thank you for this article. Too often, population is the elephant in the room that environmentalists don’t want to mention. Resources on the earth are finite. Even with more responsible choices from everybody and improvements in efficiency technology we simply cannot expect to support the growing world population indefinitely, particularly not if we hope for humanitarian reasons to help all people achieve a high standard of living. The US and other industrialized nations have lower birth rates than most third world countries, but as this article points out the environmental impact of every single new baby in the US is enormous.

    Yes, each child could grow up to be the scientist who comes up with a the technological fix for our environmental problems or the leader who creates lasting social change. However, it’s not smart to pour lots of money into a fast gambling game with a low chance of success when you could play smaller amounts of money more carefully for equal or greater odds of success. Fewer children mean we can treat each one as the precious person she or he is, investing more resources into each child’s education and health instead of trying to spread them impossibly thinly among too many needy kids.

    I love kids. I work as an outdoor educator, and the young people I teach are a joy and an inspiration every day. Nevertheless, I never plan to have kids of my own. I think it’s great (and necessary for the future of our species) that many people do want kids, but I wish they wouldn’t treat me like a freak because I make a different choice for my own lifestyle. Having kids is like eating meat: it’s an activity with a high environmental cost that people should be able to abstain from easily if they choose, while those who want to can engage in it provided they don’t do it in excess. By all means, have a child if you want one, but consider stopping at one, and if you really don’t want your kid to be an only child then stop at two.

  11. Enough poeple are having children for the future.

  12. Hello!
    Very Interesting post! Thank you for such interesting resource!
    PS: Sorry for my bad english, I’v just started to learn this language 😉
    See you!
    Your, Raiul Baztepo

  13. Thank you for finally addressing what will soon become the biggest social issue of our time. Population is the key factor in the environmental, social and political debate, yet because of the moral implications of discussing it no one will touch it.

    At it’s core it is a simple equation of supply and demand. We are currently consuming the worlds natural resources ay at a rate of 30 to 60% above sustainabilty leveles, meaning that we are taking more the we are allowed.

    That is scary statistic as India and China will surpass the US very soon in their own rates of consumption because of their fast growing middle class. So those statistics will go well over those margins soon.

    This is s course of action, reckless human birthrate will only have one result, human extinction, it is simple economics.

    We are at a rate of extinction that is at 10 000 times above the natural rate. Plants and animails are vanishing at a faster then at any time since the last mass extinction.

    Our population jumped from one billion to 8 billion in one hundred years. IN that time we managed to wipe out almost half of the worlds animals in our need to feed and house our own species.

    Face it we need a lot less people to survive no one wants to address it but its a fact. Population growth should be taking centre stage in the worlds fight for survival for it is the key reason we are in the mess were in.

  14. Thank you for taking an honest hard look at this question. It truly is the elephant in the room in any discussion of the environment and the most difficult to address as it flies in the face of our animal drive to reproduce our species. This is evidenced in the emotional reactions to this issue by many here.

    Ultimately we must take a honest look to the future of the human species and make the hard choice to control population or we will not survive.

    As a teenager I became a member of ZPG and vowed to never have children. I have kept that promise and have not regreted it. It is a myth that not having children removes your genes from the pool. The human genome is so narrow and our population so large that 90 percent of us could die without affecting our genetic diversity.

    A more valid argument for having children is the ability to pass on our culture and values. I pass on my values by educating others.

    I do not expect everyone to stop having children. We need a future generation. All I ask is that we have children mindfully.

    As important as controlling population is; curtailing consumption is also absolutly necessary. While population doubled over the last 20 years our individual consumption quadrupled and continues to rise.

    These are serious problems and I am pessimistic about our future but I will continue to work for the environment and support organization like The Nature Conservancy in the hope that the tide will be turned in time.

  15. I want to thank Peter Karieva for this inspiring article and also to all the comments that address the subject with high standards. Air polution is a mayor topic now a days and it is very likely that in less than 20 years time we will have a nearly close energy system and we will be dealing with water shortage that today is also issue. Challenges is what life is made up of so lets deal with todays challenges, learn from them and pass on what we learned to next generation.
    Of course it is very likely that US citizen will change many ways in which they used to do things from shopping to working (what’s to percentage of home businesses today and the forecast for the next ten years? I don’t want to guess but I get the feeling they will increase exponentially, reducing grately the amount of energy cost and transportation), equally the different treatmente procedures being implemented for no contamination of water and efficiente use of organic waste. The fact is that many of these solutions are kept going thanks to conscientious people, I beleive this numbers are alarming but numbers by themselves are not enough we need to reach out and impact the life of another human being and be open to be impacted by them in our being to understand that the way we are using our resources (the whole planet’s) is not the best posible way. We can use them in a more efficient way and we have the power to change it, but this will not happen over night or in one generation.
    I have two daugthers, 16 and 21 and everyday I learn from them and for them. They still depend on us their parents for most of their needs and I am developing a sustainable production model for them to learn and to live from.
    The cost of a child is really very large but what a child can contribute for the growth of society is many times grater and I will not have another child until I have sponsored at least 100 people in my environmentally conscious network, because together we are more (synergy is the 21st century fact).
    Thank you again for this eye openning article it contributed to strengthen my commitment to build a better more environmental friendly family and society, the people I sponsor are like my students and like my children we learn together.
    And The Nature Conservancy is the best guide is this trip.

  16. Hi my loved 1! I wish to say that this post is remarkable, fantastic written and come with almost all critical infos. I would like to see a lot more posts like this .

  17. Nice post

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