The title mentions not owning a car and voting, that’s not in the chart either.

You can drive 12 hummers powered by crude oil and eat steak every day at not have even a fraction of the impact of just one child. Having one less child results in a ecological-footprint reduction equivalent to 58.6 tonnes of CO2 a year. By contrast, living car-free saves 2.4 tonnes a year, eating a plant-based diet saves 0.82 tonnes a year.

Not reproducing is the single most impactful thing you can do for the environment by a huge margin.