Hooked on online shopping? It’s all right, you’re not alone. In 2016, the U.S. Census Bureau estimated that second quarter online retail sales had risen by 15.8 percent from the previous year. Globally, these sales figures are said to be growing at a rate three times faster than GDP. And unfortunately, like many habits, there’s a potential downside.

The question is about sustainability.

Before focusing on the downsides, of which there are many, let’s first look at how online shopping can have a more positive impact on the environment.

When it comes to click-buying, convenience is king. In saving you a trip to the store, online shopping has the potential to reduce cars on the road. Less cars means less emissions, and with a good system in place, a greater efficiency in delivering goods to consumers direct from warehouses to their doors, cutting out the need to first distribute to stores.

"Larger vehicles are operated by fleet operators who pay attention to their bottom line," said Gregory Shaver, a professor of mechanical engineering at Purdue University. As Shaver notes, this means that fleets are designed to “efficiently move goods,” which “translates to less fuel use. With less fuel usage, there are less carbon dioxide emissions and less greenhouse gases," he said.

That’s not to mention the efficiency that could come from reducing the need for brick-and-mortar stores. In general, stores use up a lot of resources, from energy (lights, air conditioning, etc.) to marketing gimmicks that entice you to buy certain products. Research conducted at Carnegie Mellon’s Green Design Institute found that opting to solely shop online would lead to a 35 percent reduction in energy consumption and carbon dioxide emissions.

As good as this result sounds, it comes with a big if—that is, if we were to assume that all shopping was done online. In reality, as Dan Sperling, the director of the Institute of Transportation Studies at UC Davis, explained to the New York Times, "shoppers appear to be ordering online while still driving to brick-and-mortar stores at least as much as in the past."

Rather than replacing traditional stores, e-commerce is simply complementing them.

That same Times article cited a study that indicates e-commerce may in fact be contributing to a greater increase in greenhouse emissions. In particular, the study—conducted in Newark, Delaware—found that "various emissions" had increased by 20 percent from 2001 to 2011.

Ardeshi Faghri, a professor of civil engineering at the University of Delaware and a co-author of the study, pointed to the very same delivery trucks as one of the primary sources of the problem. "Online shopping has not helped the environment," Faghri told the Times. "It has made it worse."

The results of this study, published in the International Journal of Sustainable Development & World Ecology, found that the reason for this situation came down to a knock-on effect that worsens traffic congestion. Utilizing data gathered by local transportation authorities, the authors were able to determine the effect that an increase in the amount of delivery trucks had on the roads. In general, they found a direct correlation between an increase in the amount of home shopping purchases and traffic delays, which by association leads to a greater amount of emissions.

Quoted in another article in the Guardian, Faghri offered a possible explanation for these findings. He suggested that "people are using the time they save by shopping on the internet to do other things like eating out at restaurants, going to the movies or visiting friends."

Emissions aside, there's another pertinent problem that comes with online purchases: packaging. In 2014, 35.4 million tons of containerboard were produced in the United States, with e-commerce companies, according to the New York Times, "among the fastest-growing users." And that's not even mentioning all the additional plastic cushioning, foam, bubble wrap and polystyrene/Styrofoam used to protect shipped goods.

Major online retailers like Amazon are aware of this issue. Since 2009, the popular e-commerce site has logged over 33 million responses to its “packaging feedback program." So, what is Amazon doing about it? At least when it comes to cardboard, spokesman Craig Berman told the New York TImes, the company is reducing the size of its boxes to better fit its products, and in some cases, eliminating the need for additional packaging completely. But there’s still all that foam that gets used.

Don Fullerton, a professor of finance and an expert in economics and the environment at the University of Illinois, suggests one possible solution: Make retailers responsible for taking back their packaging. This, Fullterton argues, could create greater incentives for them to create better packaging solutions.

However, Betsy Steiner, executive director for the Alliance of Foam Packaging Recyclers, disagrees with this solution. As she explained to the Gotham Gazette, the main issue with plastic packaging has to do with its weight. Due to the fact that foam and bubble wrap are so light, there is very little financial incentive from the recycling industry end, which makes its profit based on a per-ton basis output. Basically, once the foam is recycled, there's no one willing to buy it. "That's been the problem with plastics recycling globally," said Steiner. "The raw material is so cheap you just get into the chicken-or-the-egg thing."

If there's a silver lining to all of this, it's that dialogue is taking place. An article published earlier this month by the retail sector president of UPS, Greg Brown, asked, Can e-commerce and sustainability co-exist? For Brown, the onus largely falls on retailers. He offers four possible ways retailers can help make e-commerce sustainable:

Optimize and reevaluate current supply chains by "identifying areas where service needs and environmental challenges converge, and exploring new ways to drive efficiencies and reduce impact." "Tap the power of data by partnering with a logistics provider," to better determine the wants and needs of your customers and "fine-tune supply chain movement." Fuel collaboration, which involves "providing customers with a way to shift their delivery to a time and location that meets their needs, reduces the environmental impact and results in a better experience for everyone." "Measure, manage, mitigate and market: Simply, companies must take the necessary steps to manage and reduce what they can and mitigate the remaining emissions. This, in turn, demonstrates company concern that goes beyond capturing immediate revenues. This type of positioning can help support the company’s reputation and offer a competitive advantage when driving consumer preference."

As a consumer, there are also a number of ways you can do your part. Deutsche Welle recently suggested five easy steps to becoming a more eco-friendly online shopper.

Don’t opt for next- or same-day delivery: Although this method might seem more efficient, it makes it harder for delivery firms to combine shipments to specific neighborhoods. In other words, more deliveries and more emissions. Always opt for the eco-friendly packaging option: Believe it or not, these options exist, and it’s worth the few extra dollars to know you’re making a small difference. Bulk buy at brick-and-mortar stores: If you have to make a trip to the shops, try limit the amount of times you go, buying in bulk when you do to avoid regular trips. In this case, using your car to buy in bulk beats making a smaller purchase online. Cycle/walk to the store: This should go without saying, but if you have to go to the store, especially for a few small items, avoid using your car. Avoid impulse buys: Ask yourself this simple question every time you want to click "add to cart": Do I really need this?

If industry and consumers tackle the problem from either side, sustainable shopping might just become standard operating procedure, whether you're clicking on a screen or getting behind the wheel.