Sure, have fewer kids and eat less meat. Or, alternatively, vote, organize, innovate...

I've never been a huge fan of environmentalists' focus on greener lifestyle change as a means to combat climate change. It takes a collective, systemic and societal problem and seeks to solve it at the smallest, most powerless level—kinda like trying to relocate an ant infestation one little ant at a time.

Make no mistake, lifestyle changes on a wide enough level can and do move the needle. From growing electric car sales to Americans eating less beef, greener consumer choices and lifestyle changes—when taken in aggregate—are already influencing national and global emissions. It's just that promoting those changes through an appeal to our better selves will likely leave us preaching to the converted.

Katherine recently reported on a study from Lund University in Sweden, which aimed to quantify the impact that different lifestyle changes might have on an individual's carbon footprint. Here are the frontrunners:

1. Having one less child: "An average for developed countries of 58.6 tonnes CO2-equivalent (tCO2e) emission reductions per year."

2. Going car-free: "2.4 tCO2e saved per year."

3. Avoiding air travel: "1.6 tCO2e saved per roundtrip transatlantic flight"

4. Adopting a plant-based diet: "0.8 tCO2e saved per year"

Obviously, suggestion number one stands out in terms of both the relative sacrifice (for people who want kids at least!) and the impact it would have. Business Green says the figure was arrived at by calculating the "carbon impact of a new child and its descendants and dividing it by the lifespan of the parent."

But this raises the question, how far down the line of descendants do you go?! And do we really get a free pass on our own emissions because our parents are responsible? ("I never asked to be born!" yelled every teenager ever.)

This, I think, gets to the heart of why I am uneasy about a focus on individual lifestyle: Our cultural, geographical, socioeconomic and familial situations vary so much that an excessive focus on individual footprint soon falls into the purity test trap. If we're so busy arguing about which of us is greenest in a decidedly ungreen society, we fail to build a movement that can move all of us forward.

That said, studies like this can be useful in guiding our priorities. They can help as we each plot out what's realistic for us and our families. And, more importantly, they can help us to identify which policy signals—family planning policy, gas taxes, farm subsidies, city planning, etc.—are most impactful to work on in shifting the collective lifestyle choices we make.

This is actually something that the authors of the study are 100% onboard with, too. Here's how Business Green summarizes their stance:

But the paper points out that national efforts to cut emissions, from greening the energy system to introducing more sustainable public transport and improving building quality, have more scope to affect widespread emissions reductions. For example, reducing overall national emissions could make the climate impact of an additional child up to 17 times lower than current projections, the study found.

So, by all means, eat your vegan cheese or beef and mushroom burgers and walk your only child to school. It's not that you aren't making a difference. But the biggest impact that any of us can have is by prioritizing how we vote, agitate, lobby, invest, protest and innovate for changes that move beyond our own individual impacts to a shift in our collective and societal norms.

I suggest we prioritize our efforts accordingly.