Study: Global urban areas expected to triple by 2030

September 27th, 2012

lucyGlobal urban areas will nearly triple by 2030 from what they were at the beginning of the 21st century, according to a recent study published in the Proceedings of the National Academy of Science. The growth represents an expansion of more than 463,000 square miles and poses a significant threat to global biodiversity.

Lucy Hutyra, an assistant professor in the College of Arts & Sciences Department of Earth & Environment, is a co-author of the study. She was recently awarded an NSF career grant titled ‘Assessing Urban Influences on Ecosystem Processes’.  Also a new mother to a 10-week old son, Hutyra graciously took time to explain what this research means.

Can you tell us the significance of this study and why we should care about it?
Lucy Hutyra: This study gives us a vision of what our future cities and urban areas could look like if we continue on the same growth and development trajectories. While urban and population growth are not necessarily negatives, we should think carefully about how and where we want to grow our cities to minimize the environmental and societal impacts. This is the first study that gives us a spatially explicit map of what the future could look like and what the biodiversity and carbon impacts of what that land cover change could mean.

What parts of the world will see the most urban growth and how will that affect biodiversity and carbon pools?
LH: By 2030, it is estimated that we will have 5 billion more people living in cities. The United States is already a very urban country, with nearly 80% of our population living in cities. The place where we are likely to see the greatest urban expansion are Africa, China, and India. Nearly 65% of all the urban land area on the planet in 2030 will be developed during the first three decades of the 21st century. If all this development goes forward, it will encroach on or displace habitats for 139 amphibian species, 41 mammalian species and 25 bird species that are either critically endangered or endangered. Further, as forests are cleared and soils are paved to build these new cities, carbon will be released into the atmosphere amplifying climate change.

We usually think of cities, with their high carbon density, as more environmentally friendly than suburban and rural places, but this study suggests a different pattern. Can you explain?
LH: Where and how we choose to build and power our future cities will determine their environmental impacts. A compact, centralized city with integrated mass transit systems will have a very different environmental footprint than a sprawling, unplanned form of urban growth. The choices and policies that we put in place now will impact us for decades to come. Smarter, lower carbon emitting cities do not have to be more expensive to develop, but they require coordinated planning across local and regional governments.

What was your contribution to this study?
LH: My research interests are currently centered on the urban carbon cycle, thinking about the movement of CO2 between tailpipes, plants, and the atmosphere. In this study, I looked at how much tropical forest (and the carbon stored in those forests) would be cleared and estimated how much carbon would be released to the atmosphere as a result of this urban growth. While the rates of tropical deforestation for timber harvest and agricultural expansion have been slowing in recent decades, cities in the tropics are growing rapidly and encroaching into pristine tropical forests. Urban growth driven carbon losses from tropical trees alone will result in 1.38 Pg of carbon going into the atmosphere, but the land clearing will yield a whole new urban ecology and chemistry in those areas.

Can you tell us about BU’s collaboration with Harvard on a carbon analysis of Boston and what you’re learning through that project?
LH: Much of my research group is working very locally here in Boston, thinking about the metabolism of our city. Much like the human body metabolized food, Boston can be thought to metabolize carbon, consuming, transforming, and emitting carbon in all facets of urban life, from urban green spaces to commerce and industry. We are working to measure or estimate the carbon release and their impacts on one another and on the region’s carbon emissions as a whole. While we don’t yet have robust carbon policies on the national or international level, we are developing the observational and methodological framework that will allow us to verify that carbon reduction and greening goals are actually met.

You recently had a baby. Congratulations. Have you been thinking about what kind of global environment your son will be coming of age in?
LH: For the last couple of months I have been on maternity leave and am now looking at the world a bit differently. By 2030, my son will be graduating high school and entering a very different world as an adult. It’s critical that we take steps now to build smarter, more sustainable cities. We will be living with many of the urban infrastructure choices that we make now for decades, we need to consider the long-term environmental impacts as well as the short-term economic costs to build resilient cities.

Contact Hutyra at 617-353-5743 or

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