Over the course of the 25 years or so that I taught Environmental Psychology, the section of the course about actions students could personally take to help preserve the environment gradually grew shorter and eventually faded away. It was just too embarrassing. There was plenty of research on how to encourage behaviors such as recycling and energy conservation, but the payoff from these actions was so small that emphasizing them seemed to trivialize the problem of climate change. The authors of the current study have broken free of the trap of emphasizing only trivial behavior changes and have included in their research some actions that will really make a difference.

Seth Wynes, a geographer from the University of British Columbia in Canada, and Kimberley Nicholas of the Centre for Sustainability at Lund University in Sweden, analyzed 148 scenarios from 39 sources—peer-reviewed papers, government reports, and carbon footprint calculators—which estimated the effectiveness of a dozen actions that individuals could take to reduce their carbon footprint. A carbon footprint is a measure of the total greenhouse gas emissions caused directly or indirectly by a person over the course of his or her lifetime.

They confined their analysis to studies done in developed countries, since their carbon consumption is a greater danger to the climate. They assumed that the individual showed total compliance with the behavior change, even though partial compliance was possible for some actions, i.e., switching to a plant based diet. For purposes of analysis, all estimates were converted to a common metric, tons of CO₂ equivalent (tCO₂e) per year per individual. They then calculated the mean estimate of all available studies of each behavior.

The authors identified four recommended actions that would have high impact, defined as saving more than .8 tCO₂e per individual per year. In order of importance, they are:

• having one fewer child
• living car free
• avoiding air travel (one transatlantic flight)
• eating a plant-based diet

(For a better look at the chart, click here.)

A fifth behavior, switching to green energy, was not recommended due to the authors’ lack of confidence in estimates of its effect. However, the mean savings met their criterion for high impact and they included it on their chart. The remaining behaviors they analyzed were found to have either moderate or low impact.

In a second analysis, the authors tabulated the individual actions recommended in ten high school textbooks widely used in Canada, and in the official government publications of Australia, Canada, the European Union and the United States. Having fewer children and eating a plant-based diet were not mentioned in any textbook; avoiding air travel was mentioned twice and living car free five times. Textbooks emphasized behavior with moderate impact, i.e., conserve energy, or low impact, i.e., plant a tree, or behaviors whose impact could not be estimated, i.e., “raise awareness,” a textbook favorite.

The analysis of government publications produced similar results. Having fewer children and eating a plant-based diet were also not mentioned in any government publications; avoiding air travel was mentioned twice and living car free once. Most of the recommended actions were of moderate impact, such as using public transportation and buying energy-efficient products. Both the textbook publishers and the four governments avoided recommending politically unpopular actions that might cut into corporate profits.

This study is obviously not the last word on reducing carbon usage. The authors admittedly did not attempt to measure rebound effects, in which reduced consumption in one area leads to increased consumption in the same or another area, i.e., knowing you have a more fuel-efficient car, you decide to drive more. Estimates of the impact of some of these actions varied quite a bit, indicating that they may not be completely reliable. The result of the most important behavior, having one fewer child, was based on a single analysis, albeit a solid, peer-reviewed study which assigned one half of a child’s emissions to each parent, one-quarter of each grandchild, and so forth.

Nevertheless, there are good reasons to take this analysis seriously. The differences between the impacts of these behavior changes are considerable. For example, the impact of a couple’s decision to have one fewer child was the equivalent of a lifetime of conscientious recycling by 684 individuals. This suggests that the authors have probably listed them in about the correct order, and that the distinction between low, moderate and high impact choices is real and important.

Researchers have estimated that, if we are to keep warming of the planet below 2° C, per capita emissions must be reduced to an average of 2.1 tCO₂e per year by 2050. Wynes and Nicholas report that a person who eats meat and takes one transatlantic flight has used up 2.4 tCO₂e, overshooting his or her personal carbon budget by these two actions alone. The current generation of teenagers are not being adequately prepared for the drastic behavioral changes that will be required of them.

You may also be interested in reading:

The Cost of Climate Inaction

Cheaper Solar Changes Everything

Norway: On the Right Track