It is folk wisdom in certain circles that having children is just about the worst damage a person can inflict on the environment. There is an appealing logic to this idea: people consume a huge amount of natural resources, so a world with less people will result in less pressure on already strained ecosystems. Therefore, the thinking goes, having less children than you would otherwise—or abstaining from having children at all—is one of the most important choices a person can make about their impact on the environment.

At a basic level, this analysis makes sense. People—especially people in the developed world—consume a tremendous amount of resources. Having less people in the world would ease pressure on natural ecosystems. And, at a personal level, having less children would contribute to easing this pressure. There is no logical flaw in this analysis; it is all sound reasoning.

But it is incomplete.

It examines only the choices of a single couple. The problem, though, is that other people exist. And, as a result of not considering the bigger picture, this analysis comes to precisely the wrong conclusion. Which is a shame, because this line of thinking appears to hold a lot of sway with certain people. So much so that I have encountered people who have taken it to heart and are having fewer or no children as a result. The truth, though, is that if you are concerned about the environment, you should have children. Lots of them.

Let me explain myself.

At the most fundamental level, the reason that any organism exists is to reproduce. Reproduction is the defining feature of life. About 4 billion years ago, some complicated molecules started making copies of themselves. Then variations arose which were better at making copies of themselves. Further variations arose which improved their reproductive rate even more. And so on until we got the world we live in today, teaming with life, all of it oriented toward one singular purpose: reproduction.

Humans are no exception. We often lose sight of this fact because our lives are filled with such a richness of experience. But when you dig into all of that richness, it turns out that it’s actually all related to reproduction. It’s hard to see that, though, because we live pretty long lives and only have a few children, so most of our experiences are pretty far removed from the basic mechanics of sex and childbirth. But it’s ultimately all about reproduction.

The result of all this copying is that any given species will multiply until it saturates its ecological niche. An ecological niche is the way that a species makes it’s way in the world. So, the ecological niche of trees is to grow really tall and harvest sunlight. Birds, on the other hand, have a very different ecological niche: they fly around and find food sources in their environment. And bees have a very specialized ecological niche: flowers give them pollen as payment for enabling flowers to fertilize each other.

Each of these ecological niches, or ways of making it in the world, will only support a population of a certain size. There is a lot of land in the world that can support trees, but it’s not infinite. And that finite area of land determines the number of trees that can exist. Things are the same with the birds and the bees: there are only so many worms and so many flowers for each, respectively, to dine on. Now, some years may be better than others and the population of a species will expand or contract in response. But whenever an ecological niche has additional carrying capacity, it quickly gets used up.

And I do mean quickly.

Many species of animals produce hundreds or thousands of offspring for each mating pair of adults. Even among mammals, it is common to produce a handful of offspring each year. Since each mating pair of animals only needs to produce two offspring in their entire lifespan to maintain a stable population, this means there are essentially always extra offspring desperately trying to eke out a place in that ecological niche. So when there’s excess capacity, it gets filled.

It takes a pretty long time for humans to produce offspring, so you might think that humans are exempt from this dynamic, but we’re not. It does take us a little longer to grow our population in response to additional carrying capacity in our ecological niche, so we don’t swarm like locusts or rodents, but human populations can grow shockingly fast.

Here’s a thought experiment that you can easily replicate on a calculator: start with one breeding pair of humans and assume that each couple has four children (so the population doubles each generation). Then figure out how many generations it takes to get from one pair of humans to the roughly 7 billion who currently inhabit the earth. You’ll find that it only takes 33 generations. If you assume that each generation averages 30 years (so, 2 children born before the mother turns 30 and 2 children born after), that means you get from Adam and Eve to 7 billion people in less than 1000 years.

So, you can voluntarily decide to abstain from having children, but that doesn’t mean that other people will follow suit. In fact, to the contrary, evolution will rapidly weed out any tendency to abstain from having children. As a result, choosing to have few or no children will have a relatively small initial effect, but then as time goes on, the only people left will be the descendants of people who have no inclination to voluntarily forego reproduction. And they will do what life has always done: reproduce.

And then we’re back at square one.

The key to arriving at a useful course of action on this issue is accepting that you, as an individual, are powerless to control the total quantity of humans that exist, because the world will just get filled up with the descendants of other people. But you can influence the proportion of humans who think like you and share your values. And the way to do this is by having children, because your children share whatever genetic inclination you have toward environmentalism, plus they will possess whatever values you instill in them.

I anticipate that the logic of this may be a bitter pill to swallow. Strain on natural resources is an important issue—possibly the most important long term issue that we face as a species—and the thought that there is nothing that can be done to influence the total quantity of humans might be demoralizing. But the thing is that the total quantity of humans alive can be influenced. Just not by you as an individual.

Instead, it is an issue which will require collective action. At some point we—humanity as a whole—will need to act collectively to prevent over-consumption of the natural resources provided to us by this, our only home in the vastness that is the universe. It will be one hell of an undertaking; so far we haven’t demonstrated any particular talent at species-wise governance.

Ultimately, to make progress on environmental issues, people are required. People to make phone calls, people to write letters, people to post and share on social media, and, most importantly, people to vote. And because people are required, progress on environmentalism will be proportional to the number of people who care about it as an issue. So the winning strategy cannot be to choose to have no children. Because to do so is to actively contribute to a future where there are less people who care about humanity’s impact on the environment.

So have some kids.

Shoot for two. And if you take a liking to it, have a whole bunch.