With Black Friday, Cyber Monday, and the holidays right around the corner, online shopping packages will soon be making their way to doorsteps around the country.

But not many of us are stopping to think much about the environmental implications of how these package got there. We’re shopping online more than ever throughout the year, but December represents an astonishing climax of consumer activity. The US Postal Service anticipates making 850 million deliveries between Thanksgiving and New Year’s Day — shipping around 15 percent of the entire year’s packages in a little over a month. That’s 10 percent more holiday shipments than just last year, and the environmental impact is growing along with it.

In 2016, transportation overtook power plants as the top producer of carbon dioxide emissions in the US for the first time since 1979. Nearly a quarter of the transportation footprint comes from medium- and heavy-duty trucks. And increasingly the impact is coming in what people in the world of supply-chain logistics call “the last mile,” meaning the final stretch from a distribution center to a package’s destination. (The “last mile” can in truth be a dozen miles or more.)

Before the online revolution, the majority of last-mile deliveries were to stores, which tended to cluster in areas that can be more easily served by large trucks. Today, most packages are now going directly to residential addresses. We’ve traded trips to the mall, in relatively fuel-efficient cars, for deliveries to residential neighborhoods by trucks and other vehicles. The last mile today ends on our doorsteps.

Even before the rise of online shopping and residential deliveries, urban freight traffic, generated a disproportionate amount of emissions, although it represented a small proportion of overall traffic. These emissions include the greenhouse gases responsible for global warming as well as a range of other pollutants that have deleterious health impacts on communities.

And things are getting worse. Deliveries are now expected to go into neighborhoods that were never designed for freight traffic — creating congestion, noise problems, and infrastructure damage in addition to emissions. The high number of destinations, combined with the unpredictability of customer orders and the increasing demand for speedy delivery also results in trucks that are less than full making multiple trips.

The problem’s not just the mode of transport. We’re also simply buying more stuff. We used to be limited by the stores in our town and their selection. Now we can shop from almost anywhere and get almost anything — and we do.

From there, the sequence is predictable and disturbing. More shipments mean more trucks. More trucks more gridlock, more double-parking, more noise, more pollution.

We can attack these problems from several directions. First, we can make the existing freight system more efficient — even if current consumption trends continue. Second, we can change how we order online to minimize the number of shipments.

Electric trucks would be a decent start

Electric and other zero-emission vehicles are one promising route toward greener online shopping. The recent announcement of Tesla’s all-electric semi-truck was met with much fanfare. But while electric semis are promising for cleaning up the impact of long haul shipping, they won’t be on the road until 2019 at the earliest. More importantly, semis won’t fix the last-mile problem.

For one thing, cargo transported over the long haul also creates short-haul traffic. In Southern California, for example, 85 percent of all truck traffic is due to within-region trips and local deliveries.

The good news is that we don’t have to wait for future technology to swoop in and save the day: Zero emissions vehicles, including vans and small-to-medium-sized trucks, already have a range of more than a hundred miles. Studies show that more than 90 percent of the trips by parcel delivery vehicles are within a 100-mile range.

One barrier to switching to electric fleets is money, of course. The up-front cost of switching out a fleet of trucks is huge, and will almost certainly require incentives from state governments. But there are ample upsides for online retail and delivery companies. Last-mile shipping, because of its complexity, can cost 50 percent or more of the total shipping cost, and it’s in everyone’s interest to make last-mile delivery more efficient.

In addition, zero-emission vehicles typically reduce long-term costs, both in fuel and maintenance. As with other areas of energy efficiency, short-term costs can net long-term gains. (State incentives can help prod companies to focus on the long term, something they’re notoriously bad at.)

But while electric vehicles address two important problems, emissions and noise, they don’t do much about congestion, parking management, or safety.

Many futuristic solutions have been proposed for making last-mile deliveries more safe and efficient, including drones, robots — and even self-driving trucks that release drones as they drive. Other urban planners have gone back to basics: What about encouraging people to pick up their packages at central delivery points?

Companies won’t change unless consumers push them to

But a big part of the problem has to do with us — with how we’re shopping. Even without drone-equipped electric vans, online shopping would be greener than driving to local stores if we did three simple things: 1) Planned ahead and consolidated our orders so we get everything we need in fewer shipments; 2) Avoided expedited shipping (even if it’s free); 3) Bought less stuff.

We as consumers can do all these things right now, but we also need a larger public campaign.

In the US, only players like Amazon and Walmart have the clout to mount such a campaign. Slower and more consolidated shipping isn’t just better for the environment; it saves these companies money by reducing the number of trucks on the road and simplifying their logistics.

But here’s the rub: Fostering slower deliveries might decrease their competitive advantage. Amazon in particular has made its reputation in part by making it easy for shoppers to get many items within a day or two — sometimes within hours. Online consumers have learned to expect nearly instant delivery.

At checkout, you can see how Amazon tries to have it both ways: Customers are often offered an incentive to choose slower shipping, but it’s often modest — or another Amazon product they want to hook you on. But imagine if companies provided larger and more prominent incentives for consolidating purchases, picking slower shipping options, or choosing centralized pick-up locations, like “lockers” at supermarkets. Even giving consumers the option to choose a “green shipping” option without any reward — beyond a sense of virtue — would be movement in the right direction.

Right now, the profit incentive is pushing retailers in the wrong direction. We can’t expect companies to act against their own interests on their own initiative. But as consumers, we can help to reshape the market. If companies make efforts to help the environment by promoting slower, consolidated shipments, we can reward such behavior with our dollars. In turn, companies can tout their environmental responsibility, creating a virtuous circle.

In the end, the last mile problem starts with us, the citizen-consumer. The solutions can start there too.

Miguel Jaller is an assistant professor of civil and environmental engineering and co-lead of the Sustainable Freight Initiative at the Institute of Transportation Studies at UC Davis.

The Big Idea is Vox’s home for smart discussion of the most important issues and ideas in politics, science, and culture — typically by outside contributors. If you have an idea for a piece, pitch us at thebigidea@vox.com.