It’s often said that denser urban development helps reduce the emissions that cause global warming. When people live in smaller homes that require less heating and when they give up cars and take transit, they make less use of climate-impacting resources. On average, dense urban areas have per capita emissions roughly 20% lower than rural areas.
However, this positive effect is offset by the fact that more of us are living in smaller households than in the past. About a quarter of homes now only have one person in them–up from 13% in 1960. In the last 50 years, the number of homes has grown 74% quicker than the U.S. population at large. The mean household size is now 2.6 people, or 29% less than in the mid-20th century.
But sharing platforms like Uber, Airbnb, and Craigslist can help cities cut their carbon emissions, potentially becoming an important weapon in the fight against climate change, a new study suggests. The authors argue that sharing transport, housing, air conditioning, and even internet connections can mitigate the shift to smaller homes. In effect, the sharing economy–broadly defined–can make up for the shift to smaller households. “If cities can provide the social and technological infrastructure that facilitate [sharing], then it is possible that dense cities can help people leverage the benefits of sharing in the 21st century in much the same way that large households have done so in the past,” the paper, published in Ecological Economics, says.
Anders Fremsted, an economist at Colorado State University, in Fort Collins, and one of the authors tells Fast Company that the environmental benefits of companies like Uber and Airbnb are “quite modest” so far. The bigger reductions in carbon emissions come from more traditional sharing, for instance, the way apartments in big blocks share heat through their walls, or the way city folk give up personal cars in favor of taking the subway. “We shouldn’t pretend that it’s new with the advent of the sharing economy. We’ve been doing this for a long time in lots of ways,” he says.
But cities can do more to encourage sharing, from approving new development that lets people live and work in closer proximity (minimizing transport needs) to making ride-hailing cheaper and more convenient. Other policy options include closing the digital divide between rich and poor, incentivizing people to rent out their homes when they go away, carpooling, and even building more parks, which reduce the need for personal, rather than shared, space.
The historical shift to smaller homes is a big deal from a climate point of view. Putting all other factors aside, the paper calculates that per head emissions in the U.S. increased by 9% between 1960 and 2010–just because people started living in smaller households. Moreover, increasing household size in cities is less beneficial than in rural areas. Adding one adult to a rural home reduces per head emissions by 8%; doing the same in the country reduces them only by 3%.
The example of the U.S. is instructive for the rest of the world. Mirroring our experience, three-quarters of the world saw more growth in the number of households than in populations in the years 1985 to 2000. Single-occupancy homes are set to be the most common form of household by 2030, the paper says.
By 2050, 85% of people in the developed world and 63% of the developing world are expected to be urban dwellers. That creates either an opportunity to reduce emissions or exacerbate them, depending on the type of development and how much people are prepared to share resources, including homes, transport, and durable goods, the paper argues.
“Some forms of sharing rely on people looking after one another, while others are more transactional–for instance, where an Uber driver shares his car for a fee,” Fremsted says. “If we can see the climate benefits of two different types of sharing, then we should think hard about how to make as much of this happen as possible.”