Science Extract: Composting your kitchen scraps is great. But what if one single choice—like giving up your car—could slash your carbon footprint 78 times more than composting? That striking comparison comes from a new World Resources Institute (WRI) analysis that upends some conventional wisdom on sustainable living. In the quest to fight climate change, not all “green” habits are created equal. And importantly, helping people adopt the high-impact habits requires more than just goodwill or basic tips; it calls for leveraging behavioral science and reshaping the environments in which we make choices.Sustainability professionals have long talked about a “behavioral wedge” – the slice of potential emissions reductions achievable through changes in individual behavior. The term was coined in 2009, when researchers estimated that Americans could cut about 7% of national emissions through personal actions (Dietz et al., 2009). More recently, the IPCC’s 2022 report vastly expanded this vision, suggesting that comprehensive changes in demand (including lifestyles, technologies, and policies) could reduce global greenhouse gas emissions by 40–70% by 2050 (IPCC, 2022). However, the IPCC also made a critical caveat: even when people want to choose low-carbon options, realizing those big savings “requires substantial policy support” to overcome infrastructural and socio-cultural barriers. In other words, individuals can only take the behavioral wedge so far on their own. The WRI working paper “The Effective Impact of Behavioral Shifts in Energy, Transport, and Food” (April 2025) digs into this, quantifying how much various lifestyle changes can actually cut emissions – and how to bridge the gap between theory and reality.
Four Priority Shifts That Pack a Climate Punch
The authors in the WRI study identify four “Priority Shifts” – high-emission behaviors where changes can dramatically reduce an individual’s carbon footprint. These are the big-ticket actions sustainability experts say we should focus on:
Driving less (or not at all): Decreasing gas-powered car use – for example, living car-free, using public transit or biking, or switching to an electric/hybrid vehicle – tops the list of impactful changes. Going completely car-free can cut about 2.1 tons of CO₂-equivalent per person per year, a bigger annual savings than installing home solar panels and going vegan combined. In fact, transitioning away from gas cars is so critical that three of the top six highest-impact actions relate to driving (owning no car, or replacing a gas car with a hybrid or EV, or opting for transit) (Kraft-Todd et al., 2025).
Flying less: Decreasing air travel is another major opportunity. Long-haul flights rack up huge emissions, so cutting back—whether by vacationing closer to home or substituting virtual meetings for business trips—can significantly shrink one’s carbon footprint. (A single roundtrip flight from New York to London emits roughly 1 ton of CO₂ per passenger in economy; avoiding multiple flights adds up fast.)
Cleaning up home energy: Lowering residential fossil fuel use through structural changes – such as installing solar panels, improving insulation, upgrading to efficient electric appliances or heat pumps – is the third priority. These upgrades tackle emissions at the source. For example, putting solar panels on your home can save roughly 1 ton of CO₂ per year, making it the third most impactful shift overall. Simply conserving energy or buying efficient gadgets helps too, but those “superficial” changes yield only about half the impact of bigger structural moves like going solar or downsizing energy needs. The key is not just using a bit less power – it’s about changing where the power comes from and how much you need in the first place (Kraft-Todd et al., 2025).
Eating a plant-rich diet:Reducing consumption of animal-based proteins – especially red meat and dairy – is the fourth priority shift. Diet shifts can have profound effects because producing meat (particularly beef and lamb) and dairy generates far more emissions than plant-based foods. Going fully vegan (no meat, no dairy) was found to cut nearly 1 ton of CO₂ per year – about double the impact of a vegetarian diet that still includes dairy. Even just eating less meat, if not entirely vegetarian, can capture roughly 40% of the emission savings of going full vegan (Kraft-Todd et al., 2025).
These four shifts offer outsized climate benefits, particularly for those of us in high-consuming lifestyles. And they are especially relevant in wealthier societies – after all, one needs to have a car or frequent flights or daily meat in order to cut them. By contrast, many popular eco-friendly habits we hear about have a much smaller impact on greenhouse emissions. The WRI study calls these “Supplementary Shifts”. They include things like recycling and composting, reducing food waste and packaging, turning off lights, or upgrading to efficient appliances. These actions are worthwhile – they often have other benefits like waste reduction, and every bit of CO₂ saved helps – but their climate impact is comparatively tiny. The difference in emissions between behaviors is, as the report puts it, staggering. Living car-free saves about 2.1 tons of CO₂ per year, whereas composting all your food scraps saves only around 0.027 tons. That means one person giving up their car does as much for the climate as 77 people starting to compost . Likewise, installing solar panels on your home has roughly 42 times the impact of diligent composting. These comparisons aren’t meant to discourage the smaller green habits, but they highlight a crucial point: to really move the needle on emissions, we have to prioritize the big stuff. As the researchers put it, prioritization is critical – both individual attention and public policy need to shift toward enabling the highest-impact behaviors.
Mind the Gap: When Potential Meets Reality
If changes like ditching cars, flying less, solarizing homes, and eating plant-based are so impactful, one might ask: why aren’t these practices widespread already? Here’s where behavioral science — and some hard realities — come into play. It turns out there’s a sizeable gap between the theoretical emissions savings from these shifts and what’s achieved in practice. The WRI team calls this the “effective impact.” In an ideal scenario, an individual who did all the top actions (no car, no flights, vegan diet, solar-powered efficient home) could cut their carbon footprint by an estimated 6.5–7.2 tons of CO₂ per year, roughly equal to the entire annual emissions of an average global citizen (for context, the world per capita average is about 6.3 tons CO₂e/year, though it’s much higher in countries like the U.S. and much lower in places like India). However, in the real world, the study finds only about 10% of that potential is being realized. In other words, individual actions in our current society are achieving just a fraction of the emissions reductions they could in theory.
Why this big shortfall? The simple answer: it’s hard for people to consistently make these big changes in the face of economic, social, and infrastructural barriers. Human behavior isn’t driven purely by knowledge or good intentions; it’s shaped by convenience, norms, costs, and our own cognitive biases. Behavioral economists point to factors like present bias – we tend to favor immediate comfort or savings over future benefits. For example, someone might opt for a cheaper gasoline car today rather than an electric vehicle with higher upfront cost, even if the EV would be cheaper and cleaner over its lifetime. There’s also the power of social influence – our choices often mirror those of our peers. If one lives in a community where driving SUVs and eating beef are the norm, bucking that trend is psychologically harder. As the WRI paper notes, burger-centric norms can discourage someone from ordering the veggie option, but if they start seeing friends and neighbors shift toward plant-based diets, that sustainable choice becomes more palatable.
Then there’s the sheer force of habit and environment. Social psychologist Kurt Lewin famously described human behavior as a function of the person and their environment – a “tension system” of driving and restraining forces. Small tweaks to our environment, or choice architecture, can have outsized effects on behavior. Think of how adding protected bike lanes in a city suddenly encourages more people to cycle, or how simplifying the process for home energy retrofit rebates can spur more homeowners to insulate their attics. These are examples of enabling forces nudging behavior. By the same token, our environments often contain restraining forces that keep us locked into high-carbon habits. If the only convenient way to get to work is by driving, if flights are subsidized while rail travel is scarce, if vegetarian options are hard to find or expensive, people’s default behavior will gravitate to the higher-carbon choice, even if they care about climate change.
Behavioral science has identified a toolkit of interventions to help people change behavior: from providing information and feedback, to setting defaults, to using social comparisons (“your neighbors use 20% less energy than you”), to incentive rewards or penalties, to commitment devices (asking people to pledge to a goal or put some “skin in the game” toward achieving it). The WRI study looked at dozens of real-world experiments and programs using these tools – collectively covering over 1.3 million individuals – to see what works best to shift the big four types of behaviors. The good news is interventions do make a difference. On average, programs that applied behavioral insights led to about a 10 percentage point improvement in the adoption of the target sustainable behavior compared to a control group. In behavioral science terms, that’s a meaningful bump. And some approaches stood out as especially promising: tweaking the choice environment (for example, making the climate-friendly option the default, or framing choices in a way that highlights the better choice) and commitment-based approaches (asking people to publicly commit or set a goal, like a pledge to fly less or a deposit that they only get back if they meet an energy-saving target) tended to yield stronger effects. By contrast, some popular methods were less effective than one might think – simply providing more information (like carbon footprint calculators or educational campaigns) or relying on mild social nudges (like generic “others are doing it” messages) often showed the smallest impacts on behavior. In short, making it easy and making it a commitment beat making it informational.
Notably, the WRI researchers found a geographic gap in behavioral research: much of the data on what interventions work comes from the U.S. and Europe, whereas there’s a deficit of studies in major emerging economies like Brazil, China, and India. This highlights the need for more context-specific research and pilot programs in those countries. Cultures, infrastructure, and economic conditions differ, so strategies to shift diets or transit use in India might need to differ from those in Europe. The overarching lesson from the WRI study is that behavior change and system change are two sides of the same coin. To meet our climate goals, we must scale up both. When sustainable behavior becomes the path of least resistance for billions of people, we’ll not only cut emissions – we’ll build a world that is healthier, more equitable, and resilient for generations to come. In the end, our everyday choices do add up, especially when the world around us is designed to help us choose wisely.
