According a study from Wynes & Nicholas, Environmental Resarch Letter, 2017, the most impactful individual action is to have less children (by far more effective than the other ones). Next, come changing mobility habits and living without a car, followed by avoiding a transatlantic flight and buying greener energy. 

You can find the impact in tonnes of CO2 equivalent per year of each of those actions in the following table: 

Of course, having less children is a drastic and life-changing decision. To ensure a long-lasting change of personal habits, many companies are working on solutions that make sustainable choices easier. 

Beside, it’s recommended to start with the easiest steps, and the following ones will come much more naturally.