In 2008, humans became a majority urban species for the first time. Today, up to 54 per cent of people live in cities, and that number is only set to rise. Climate change will impact the cities and towns we live in—many urban areas will have to change significantly, and rapidly, in order to withstand the pressures of increasing dangerous weather events, heat waves, and other climatic dangers. However, according to the United Nations Human Settlement Programme, urban settlements account for 60–80 per cent of all carbon emissions, meaning that how we live in those cities and towns will also have a significant impact on how climate change progresses, and whether we have any chance of mitigating its impacts.

There are a huge number of factors which will have to be considered in order to green our cities. One of these, of course, will literally be how green they are—not only are green spaces like parks and gardens important for carbon sequestration and biodiversity, but the shade trees provide can significantly reduce the urban heat island effect. This is the effect by which the materials of which cities are built—“dense dark surfaces such as bitumen on roads”—trap heat during the day, and keep the city warmer at night, with the eventual impact that average temperatures in urban areas are three to four degrees higher than surrounding, non-urban areas. For this reason, The Guardian reports, the Melbourne City Council is aiming to “double the tree canopy cover from 22 to 40 per cent by 2040, by planting about 3,000 new trees a year”—an important policy, given that the higher and higher temperatures projected during Australian summers in coming decades will have serious health impacts, particularly when combined with the urban heat island effect.

Another issue requiring urgent consideration is where growing cities should grow. As more and more of the population moves or is born into cities, the amount of space they take up necessarily increases. Generally it is accepted that there are two ways this can go—out or up. We can embrace urban sprawl and allow cities to spill out into valuable farmland and wild spaces, or we can replace low-density detached houses with skyscrapers, allowing far more people to live in the same amount of ground space.

There are obvious issues with allowing urban sprawl to continue indefinitely—aside from the destruction of wilderness areas, a lot of valuable farmland is located around the city fringe. This is particularly true in Melbourne, where the foodbowl located around the city produces “47 per cent of the vegetables grown in Victoria and around eight per cent of fruit”, according to a Foodprint Melbourne report from 2015. By 2050, when Melbourne’s population is predicted to reach at least seven million, “Melbourne will require 60 per cent more food to meet the population’s needs,” but “around 16 per cent of the farmland in Melbourne’s foodbowl” could be lost to the urban sprawl occurring as a result of this growth. While currently the area around Melbourne “produces enough food to meet around 41 per cent of the food needs of greater Melbourne’s population,” they say that by 2050 this could be reduced to as little as 18 per cent. Food would then have to travel to the city from further away, likely via fossil-fueled transportation.

Furthermore, outer suburbs tend to be less well-serviced in terms of infrastructure than older inner suburbs—in particular, there tends to be far less public transport than closer to the city centre. As more people are forced further out by the lack of space and affordable housing, there will be a significantly increased reliance on cars, given that most jobs will continue to be located closer to the CBD. Obviously, this will mean far more fossil fuels used, and could also create serious issues for residents of outer suburbs as fossil fuels become more expensive, and people become less able to transport themselves into areas where jobs are more readily available.

However, simply building up instead is by no means a perfect solution. More large concrete buildings will contribute further to the urban heat island effect, and densely populated areas often struggle more with issues of polluted air and water. Many apartment buildings going up at the moment are cheap, pre-fabricated concrete blocks which may only last a handful of decades—obviously a hugely wasteful way to build—and which take the place of better quality houses.

Living in cities in a sustainable way will require holistic planning and massive changes to the way we organise our spaces. There are the obvious elements, such as investment in public transport, and new green spaces—Melbourne City Council’s plan for Southbank Boulevard seems a step in the right direction, with its new bike lanes, green tramway, and focus on biodiversity in the inner city. However, ensuring that housing in the greener inner city and suburbs remains affordable and available will be more difficult, and could require changes to the expectations about how we share space. Having individuals or small families in their own houses no longer seems practical—instead, retrofitting our suburbs to accommodate more people by establishing more housing co- operatives, living in a more communal way, may be necessary. The expectation that adults, particularly with families, leave sharehouse situations for their own space is a deeply entrenched one, but to avoid cities sprawling out we will have to learn to share space in a new way.