Fighting climate change is going to require massive changes in our shopping habits

As countries move slowly on climate change, many cities–which account for more than 70% of global CO2 emissions and can act more nimbly in terms of policy–are working to fill the gap. Paris, San Francisco, and others are moving to 100% renewable electricity. Los Angeles is working to help get Angelenos out of cars and aiming for zero emissions transportation by 2050. Milan is planting 3 million trees. New York City is retrofitting skyscrapers.

But a new report from C40, a network of the world’s largest cities that focuses on climate action, makes it clear that cities need to go beyond what’s happening inside city limits and also tackle emissions from products that end up there–from food to mobile phones to clothing. If a pair of jeans is made in a factory in Vietnam running on coal power, crosses the ocean in a cargo ship running on dirty fuel, and then gets in a truck running on diesel, the person who buys those jeans in San Francisco bears some responsibility for that total footprint.

After analyzing emissions in its member cities along with experts from Arup and the University of Leeds, C40 found that consumption in those cities is responsible for 10% of global emissions. To avoid the worst impacts of climate change, it says, emissions from consumption in high-income cities need to drop by two-thirds within a decade. “If you don’t look at consumption, you’re missing out on a chance for urban consumers, for businesses, for citizens, to influence a much bigger piece of the pie,” says Tom Bailey, a senior research manager at C40 Cities.

Changing consumption may in some ways be even more challenging than transitioning to renewable electricity, since it involves so many pieces. But there are changes that are feasible to make. In São Paolo, for example, where the city is responsible for serving meals to 1.1 million students, the government is prioritizing plant-based food. In Europe, some cities are beginning to collaborate with clothing companies on new approaches for a more circular economy that can limit waste. By improving public transportation and bike lanes, cities can make it easier for citizens to avoid buying cars. The report looks at six key sectors and other opportunities for cities to intervene. Many of the changes would have benefits beyond climate: if people eat less red meat and more vegetables and fruit, it could prevent 170,000 deaths a year in C40 cities. If they consumed clothes differently, residents in C40 cities could save $93 billion, collectively.

Some cities are already starting to make changes. Now that the report has calculated how much consumption matters, others will likely begin to consider new strategies. “This is a new area for many, for many, so we’re not expecting our city to go away tomorrow and commit to these targets,” says Bailey. “We’re definitely hoping that this will start a really robust conversation.”