The debut of electric scooter programs in cities such as Austin, Washington D.C. and San Diego has been making headlines with promises of cleaner air, but is this really the case? Between LimeBike, Waybots, Spin and Bird, which has been newly introduced to the Los Angeles area, there is a plethora of companies jumping on the trend of promoting eco-friendly scooters to city planners and residents. With public transportation methods significantly improving in environmental efficiency — and the majority of distances traveled by scooter being walkable distances — the carbon footprint might not be as small as scooter-share programs are claiming.

“Today, 40 percent of car trips are less than two miles long,” said Travis VanderZanden, founder and chief executive of Bird. “Our goal is to replace as many of those trips as possible, so we can get cars off the road and curb traffic and greenhouse gas emissions.” The scooters are the latest trend to enter the app-based mobility market, which has passengers whimsically racing through city streets at a $1 rental price, plus 15 cents for every minute after.

Related: Paris launches electric scooter sharing program with Coup and Gogoro

While Bird is assuming that half of its scooter rides are replacing mile-long car trips, Phil Lasley, who has been studying traffic, bicycle and pedestrian issues for the Texas A&M Transportation Institute said, “We honestly don’t know yet.” According to his evaluations, it is possible that the scooters are replacing short drives but with quantities still uncertain. He said there are many other aspects to consider.

“Are these trips taking away from other bicycle trips? Are they taking away from transit? Are they taking away from walking?” Lasley asked. For instance, a mile-long trip to the office means that the 15-mph vehicle would charge for a minimum of 4 minutes plus extra for time in traffic. This exceeds the average public transportation fares for cities such as Austin and L.A., where the average full-fare ticket only costs $1.25 to $1.50 and can get you a lot farther.

City bike-share programs are available at comparable rates to those of public transportation, as seen with L.A.’s new bicycle advertising campaign. The green transit platform is promoting the city’s carbon-free single rides at the same cost as a bus or metro ticket, while daily users of a monthly plan are seeing fractions of a dollar for their commute cycles. It goes without saying that owners of bikes, non-motorized scooters and skateboards are at a monetary and ecological advantage in comparison to those using electric scooters.

Related: Gogoro revs up Smartscooter expansion with $300 million in new funding

From an economic standpoint, Bird and LimeBike rides might be behind compared to alternatives such as buses, trains and bikes. But according to a Bird press release on its Austin launch, “Riders were able to prevent 445,334 pounds of carbon emissions.” LimeBike similarly claimed an estimated 8,500-pound reduction in carbon dioxide emissions in Austin in just two weeks.

“With the launch of Lime-S, we are expanding the range of affordable, space-efficient and environmentally friendly mobility options available to D.C. residents,” said Jason Starr, a LimeBike executive for the company’s Washington D.C. division, back in March. With competing green vehicles focusing on both affordability and environmental friendliness, many people are looking to “space-efficien[cy]” to account for the hype of electric scooters.

The space efficiency feature makes electric scooters fun to ride and easy to park anywhere, but it also means that chargers are driving long distances to pick up the scooters one by one. Each morning, electric scooters are dropped off en-mass at various hubs throughout the city. From there, riders can take the vehicles and drop them off wherever they wish within the city. Scooters now litter random sidewalks, storefronts and restaurant walkways — rarely in a collective group. At night they are “captured” (in the case of Birds) by the company’s chargers, who are individual citizens signed up to make money by collecting, powering and redistributing the scooters to the hubs each morning.

Each scooter has a price tag on it, with those more difficult to collect scoring the charger a higher paycheck. The higher valuations on the remote scooters means that chargers are likely to drive farther to and from the stranded scooters, consuming more gas and emitting more carbon dioxide in the process. Similarly, morning commuters who wake up to find an empty dropping pad might eagerly run back to their reliable, personal vehicles instead of public transportation, because they are in a time-crunch. Whether these factors are being taken into account by the companies in their statistics is unclear.

Related: Lyft is making all their rides carbon neutral

Their popularity is as much their undoing as it is their achievement according to Haje Jan Kamps, portfolio director at venture capital firm Bolt. The entrepreneur recently published a piece on TechCrunch about the business models e-scooter companies would need to adopt in order to succeed. “They are currently in a massive scaling mode and so the only concern they have, really, is to get as many scooters on the roads as possible and as many rides as possible for each individual scooter,” Hamps said. “There is a real risk that some of the things like reusability or recyclability might be first on the chopping block.” The scooters are estimated to have a two-year life span, meaning they could end up in landfills at the end of their short life-cycle.

This is something that Lasley agreed with. “It appears that these services are being heavily used,” he said, adding that the more popular they become, the more waste they will create.

While we want to love the fun idea of electric scooters, it is clear that some things need to be improved. For these new companies, a learning and improvement process is to be expected. We are eager to see where these companies are headed in terms of creating a more eco-friendly product.

Via Austin Monitor, The Washington Post (1, 2) and Chester Energy and Policy

Images via Elvert Barnes (1, 2), Luis Tamayo and Tim Evanson