The US has become a nation of suburbs. But will it stay that way?

The American dream in Highland, California. Image: Getty.

Since 1970, more Americans have lived in the suburbs than central cities. In 2010, suburbanites outnumbered city and rural dwellers combined for the first time. Americans live in a suburban nation.

Despite several concerted efforts by city governments to lure residents, suburbanisation continues largely unabated. Census figures from earlier this year show that suburbs of warm climate “Sun Belt” cities in the South and West continue to grow, while cities in the cold climate “Snow Belt” of the Midwest and Northeast decline.

Smaller metropolitan areas with fewer than 500,000 people have also grown, related to an improving economy and job creation in smaller urban centers. This ongoing shift towards the suburbs has significant environmental repercussions.

Since cities and suburbs are home for 8 of every 10 Americans, views of the country are often distorted. Most travel occurs within or between cities. Although rural areas have more than three times the miles of roadways as urban areas, more than two-thirds of the 3trn miles that vehicles travel each year in the U.S. are in urban and suburban areas.

Jobs, too, are overwhelmingly centered around cities. Less than 2 per cent of the American labor force is employed in agriculture.

Many of my students are surprised that the land area occupied by cities is only 3 per cent of the nation’s territory. However, they are correct in that cities have an outsized impact on the economy. In 2016, metropolitan areas contributed $16.8trn to the nation’s gross domestic product, more than 90 per cent of the country’s economy.

With this economic activity comes a high use of natural resources and concentrated pollution production. Although density can be more efficient when it comes to energy use, the sheer number of urban dwellers means that cities, despite a small physical footprint, have a big energy and pollution footprint.

Rising suburbanisation undermines some of the energy efficiency gained by high density living in urban cores. Manhattan has lower per capita greenhouse gas emissions than the suburbs of New York, thanks to factors like apartment living, high costs of car ownership and extensive public transit. Of course, not everyone can afford to live in Manhattan even if they want to. Low-density suburbs are an affordable alternative.

Even so, suburban life can look less desirable. As the U.S. population ages, elderly people may end up “stranded in the suburbs,” far from adequate public transit and unable or unwilling to drive. At my urban university, a mixed use retirement facility was sold out before ground was broken. In the U.S., there are more than 100 university-based retirement communities and the number is growing.


The trend toward suburban life could soon come to an end. Millennials – the generation born between 1981 and 1997 – appear to prefer urban life. They are happier in cities, especially large metropolitan areas, than older generations. The millennial population is growing fastest in metro areas in the Sun Belt and western states, and slowest in the Snow Belt. Topping the list of the fastest-growing metropolitan areas for millennials are Colorado Springs, San Antonio, Denver and Orlando.

Will millennials follow older generations to the suburbs as they marry, have children, recover from the shocks of the Great Recession and find affordable housing? The jury is still out.

Whatever happens, it’s unlikely that people will start to move out of cities and suburbs and back into rural areas. Even though increased connectivity and the internet of things will make remote work more possible than before, businesses will continue to concentrate in urban cores, because they profit from being close to one another. (Futurists once thought the telephone would make crowded cities unnecessary.)

I believe that it’s likely the U.S. will remain a nation of suburbs for some time to come. That will pose a continuing environmental challenge. But it will also bring a new set of opportunities for millennials, who are predicted to overtake baby boomers by next year as the largest generation in the country. How will that generation remake the suburbs to suit their needs and desires without exacerbating current environmental challenges? The answer has profound implications for the nature of cities and urban life in the U.S.

The Conversation

Christopher Boone, Dean and Professor of Sustainability, Arizona State University.

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Green roofs improve cities – so why don’t all buildings have them?

The green roof at the Kennedy Centre, Washington DC. Image: Getty.

Rooftops covered with grass, vegetable gardens and lush foliage are now a common sight in many cities around the world. More and more private companies and city authorities are investing in green roofs, drawn to their wide-ranging benefits which include savings on energy costs, mitigating the risk from floods, creating habitats for urban wildlife, tackling air pollution and urban heat and even producing food.

A recent report in the UK suggested that the green roof market there is expanding at a rate of 17 per cent each year. The world’s largest rooftop farm will open in Paris in 2020, superseding similar schemes in New York City and Chicago. Stuttgart, in Germany, is thought of as “the green roof capital of Europe”, while Singapore is even installing green roofs on buses.

These increasingly radical urban designs can help cities adapt to the monumental challenges they face, such as access to resources and a lack of green space due to development. But buy-in from city authorities, businesses and other institutions is crucial to ensuring their success – as is research investigating different options to suit the variety of rooftop spaces found in cities.

A growing trend

The UK is relatively new to developing green roofs, and governments and institutions are playing a major role in spreading the practice. London is home to much of the UK’s green roof market, mainly due to forward-thinking policies such as the 2008 London Plan, which paved the way to more than double the area of green roofs in the capital.

Although London has led the way, there are now “living labs” at the Universities of Sheffield and Salford which are helping to establish the precedent elsewhere. The IGNITION project – led by the Greater Manchester Combined Authority – involves the development of a living lab at the University of Salford, with the aim of uncovering ways to convince developers and investors to adopt green roofs.

Ongoing research is showcasing how green roofs can integrate with living walls and sustainable drainage systems on the ground, such as street trees, to better manage water and make the built environment more sustainable.

Research is also demonstrating the social value of green roofs. Doctors are increasingly prescribing time spent gardening outdoors for patients dealiong with anxiety and depression. And research has found that access to even the most basic green spaces can provide a better quality of life for dementia sufferers and help prevent obesity.

An edible roof at Fenway Park, stadium of the Boston Red Sox. Image: Michael Hardman/author provided.

In North America, green roofs have become mainstream, with a wide array of expansive, accessible and food-producing roofs installed in buildings. Again, city leaders and authorities have helped push the movement forward – only recently, San Francisco created a policy requiring new buildings to have green roofs. Toronto has policies dating from the 1990s, encouraging the development of urban farms on rooftops.

These countries also benefit from having newer buildings, which make it easier to install green roofs. Being able to store and distribute water right across the rooftop is crucial to maintaining the plants on any green roof – especially on “edible roofs” which farm fruit and vegetables. And it’s much easier to create this capacity in newer buildings, which can typically hold greater weight, than retro-fit old ones. Having a stronger roof also makes it easier to grow a greater variety of plants, since the soil can be deeper.


The new normal?

For green roofs to become the norm for new developments, there needs to be buy-in from public authorities and private actors. Those responsible for maintaining buildings may have to acquire new skills, such as landscaping, and in some cases volunteers may be needed to help out. Other considerations include installing drainage paths, meeting health and safety requirements and perhaps allowing access for the public, as well as planning restrictions and disruption from regular ativities in and around the buildings during installation.

To convince investors and developers that installing green roofs is worthwhile, economic arguments are still the most important. The term “natural capital” has been developed to explain the economic value of nature; for example, measuring the money saved by installing natural solutions to protect against flood damage, adapt to climate change or help people lead healthier and happier lives.

As the expertise about green roofs grows, official standards have been developed to ensure that they are designed, built and maintained properly, and function well. Improvements in the science and technology underpinning green roof development have also led to new variations on the concept.

For example, “blue roofs” increase the capacity of buildings to hold water over longer periods of time, rather than drain away quickly – crucial in times of heavier rainfall. There are also combinations of green roofs with solar panels, and “brown roofs” which are wilder in nature and maximise biodiversity.

If the trend continues, it could create new jobs and a more vibrant and sustainable local food economy – alongside many other benefits. There are still barriers to overcome, but the evidence so far indicates that green roofs have the potential to transform cities and help them function sustainably long into the future. The success stories need to be studied and replicated elsewhere, to make green, blue, brown and food-producing roofs the norm in cities around the world.

Michael Hardman, Senior Lecturer in Urban Geography, University of Salford and Nick Davies, Research Fellow, University of Salford.

This article is republished from The Conversation under a Creative Commons license. Read the original article.