Fast, free shipping has an environmental cost

“The time in transit has a direct relationship to the environmental impact,” says Patrick Browne, director of global sustainability at UPS. “I don’t think the average consumer understands the environmental impact of having something tomorrow vs. two days from now. The more time you give me, the more efficient I can be.”

“The efficiency and those benefits of delivery came from consolidation and sharing a big vehicle,” Goodchild says. “And as we move away from that, if we move towards basically paying someone to make a trip for us, a lot of those benefits are eroded.”

In the worst-case scenario, with one delivery per trip, the carbon emissions can be as much as 35 times greater than they would be for a fully-loaded delivery van. That doesn’t happen very often, but contracted last-mile courier services — like Amazon Flex and Walmart’s Spark Delivery — may be delivering only a few orders at once, often in a personal vehicle or small van. What’s more, many consumers are ordering online and still making trips to the store, meaning there are just more cars on the road.

With great scale comes greater efficiency

Inefficient routes are not only more carbon-intensive — they’re also more expensive for the shipper. If fast delivery is free, it’s only because the retailer is subsidizing that delivery to fight for customers at a time of fierce competition and rapid growth. That means consumers aren’t feeling the true cost — either environmental or financial — of getting their e-commerce goods super quickly.

“There are some companies that can absorb the cost,” Jaller says. “One of them — it’s one of the largest ones — has been absorbing the logistic cost for a while. And it’s in the billions of dollars per year.”

Jaller was referring to Amazon. For its part, Amazon says that the bigger it gets, the more efficient it can be. The news that Prime was transitioning to one-day shipping came with the announcement of an $800 million investment in logistics infrastructure, like fulfillment centers, trucks and smaller distribution hubs close to population centers.

“Prime Free One-Day is possible because we’ve been building our network for over 20 years,” a spokesperson said in a statement. “This allows Amazon to work smarter based on decades of process improvement and innovation, and to deliver orders faster and more efficiently.”

There are a few other companies that might be able to rival that level of proximity to the customer and volume of goods, which allow them to consolidate deliveries even at a fairly rapid rate. Walmart, for one, has more than 4,700 store locations and an extensive network of warehouses from which it can deliver packages, so trucks don’t have to visit multiple locations.

Some third-party logistics providers also say they are big enough to offer same or next-day service for retail clients without sacrificing carbon efficiency. XPO Logistics is among the largest, with 90 facilities across the country, and says it uses machine learning algorithms to direct where inventory should be stored.

“We look at who’s buying the products from where, and who’s returning products to where, and are able to forecast where to have the products strategically positioned nearby the consumer,” says XPO’s chief information officer Mario Harik.

“I would not say [Amazon is] pretty environmentally friendly,” Jaller said. “I would say less environmentally bad than others.”

The tradeoff between speed and carbon emissions gets larger with smaller retailers that make more custom deliveries, from meal kit services to subscription razor companies — but they feel they need to match the shipping convenience of market leaders to maintain their foothold. And when things are free, people tend to consume more of them, which could raise overall emissions even further.

Still, it’s pretty clear that the climate would benefit if everything slowed down a little. If consumers were more aware of the impact of their ordering choices, they might think twice about asking for things as soon as possible. Especially if it’s something they don’t really need immediately, like a new rug.

Fortunately, behavioral economics has a lot to say about this problem.

There is an answer: Just nudge

“Nudging,” or leading consumers to make the best choice on their own without seeming bossy about it, is a tactic used everywhere from health care to traffic enforcement. Utility ratepayers have been persuaded into using less power and water by invoices that tell them how much they’re consuming compared to their neighbors — bringing the power of guilt and social norms to bear on decision making. Similarly, hotels invite guests to keep their towels rather than replacing them with fresh ones each day in order to conserve resources.

There is already evidence that e-commerce consumers may be able to be gently pushed toward less harmful choices. Josué Velázquez Martínez, a research scientist at MIT’s Center for Transportation and Logistics, found in a test in Mexico that 52% of consumers were willing to wait longer when told at checkout that slower shipping would save trees.

Sometimes all that needs to happen is reframing the decision, by “relabeling” standard shipping as “green shipping,” and making it the default option so that shoppers have to pro-actively choose the faster speed rather than the other way around.

Jenic Mantashian, executive vice president of behavioral science consulting firm BVA Nudge Unit, says you could even give people points or badges for picking the greener option that can be redeemed for discounts.

Many people want to be seen as responsible. Companies could leverage that self-consciousness and create a “virtue signal” to neighbors — put slower-shipped boxes in a different color — without having to raise prices.

“We’ve seen traditional economic incentives work, in terms of changing behavior,” Mantashian says. “But we’ve also seen how your personal core values and what you’re trying to achieve as a human being is super important.”

“If they paid the true price of that delivery, they would ask themselves if they really needed it sooner,” says Goodchild. “I think that the fundamental idea of really paying for what it cost in terms of traffic congestion and emissions is something we don’t do right now. The more we did, the more balance there would be in what people are asking for and what people are willing to buy.”

It may be true that the best things in life are free — but in this case, it’s usually because the earth is paying for it down the line.

— CNN Business’ John General and Richa Naik contributed reporting.