The pandemic, in effect, hit overdrive on a decadeslong shift toward online shopping. E-commerce sales jumped nearly 32 percent in 2020 compared to the prior year, according to U.S. Census Bureau data.  So far this year, online sales are on track to outpace that record. To meet the demand, delivery companies such as Amazon, FedEx, UPS and food delivery services wrapped millions of purchases in layers of cardboard and plastic and hired thousands of new drivers to bring them to our doorsteps. Now, cities, climate scientists and companies are trying to figure out the consequences for the planet.

In the decade or so prior to Covid, fewer than 10 academic studies explored whether e-commerce or in-person shopping is better for the environment. In general, the studies that were done found that online shopping produced fewer carbon dioxide emissions than traditional brick-and-mortar retail. The most recent research is starting to incorporate more of the complexities of retail. In January, MIT’s Real Estate Innovation Lab published a study that simulated hundreds of thousands of those kinds of scenarios and found online shopping to be more sustainable than traditional retail 75 percent of the time.

But consumers today aren’t choosing one or the other, underscoring just how tricky this assessment is.  The MIT researchers recommended how shoppers and policymakers could help reduce carbon footprints at various steps of the supply chain, because either way, people are buying more. “This is so much more complicated than, ‘E-commerce is better than brick and mortar,’” said Dr. Andrea Chegut, director of the lab. “We’re not on a good trajectory, because everyone is using both strategies. So on the aggregate, there will be more emissions.”