Within twenty years, the world's urban areas are going to grow – a lot. A recent study in the Proceedings of the National Academy of Sciences predict that urban areas will expand 463,000 square miles by 2030, especially in China and India. That’s a lot of new roads, buildings, and hospitals and the study by researchers at Yale, Boston University and Texas A&M estimate somewhere between $25 and $30 trillion worldwide is expected to be spent on infrastructure.
To help understand what this all means the Green Blog asked Lucy Hutyra, an assistant professor at BU and one the study's co-authors to answer some questions. Here is an edited version of her responses.
What does this vast expansion of urban areas mean for the environment? Between the year 2000 and 2030, our projections suggest that the amount of urban land area will more than triple, increasing by nearly half a million square miles to accommodate 5 billion new urbanites. All of this urban growth means new development, infrastructure, and consumption that all have direct and indirect impacts on our environment.
Can you describe your contribution to the research? My research focuses on the movement of carbon within urban environments, including carbon moving through vegetation and emissions from fossil fuels. For this study I calculated the carbon emissions consequences of clearing forests in the tropics to make room for new cities. The clearing of tropical forests is particularly important of their large stature and the vast amounts of carbon they store. While the rates of tropical deforestation have been decreasing in recent decades, urban areas have been increasing. Carbon losses from just the wood in tropical forests will contribute about 5% to our deforestation emissions. Beyond those direct, immediate impacts of clearing forests for cities, the soils, habitat, and climate of the area will also change by replacing forests with roads and buildings.
How can or should urban planning change to account for these greatly expanded cities? Most of this new urban environment has yet to be built. We have a tremendous opportunity to shape where people live, how they commute, their energy efficiency, and how much green space is retained within our urban areas. There is no magic formula for optimal development patterns for all places at all times, but the choices that we make now will be in place for decades. We need to especially consider the short- and long-term consequence of our energy and transportation infrastructure as those choices are not easily redeveloped.
How will carbon emissions change from the expansion?
Where and how we chose to build and power our future cities will determine their carbon impacts. A compact, centralized city with integrated mass transit systems will typically have a smaller carbon footprint than a sprawling, unplanned form of growth. Urban areas are currently estimated to be responsible for approximately 70% of our global CO2 emissions. There is enormous potential to impact our per capita emissions through urban efficiencies, such as reducing single occupancy vehicle commuting distances and increasing building energy efficiencies. Smarter, lower carbon emitting cities do not have to be more expensive to develop, but they require coordinated planning across local and regional governments.
You are also studying "carbon metabolism" in Boston. Can you explain what that is and your research? The carbon metabolism concept is an analogy that allows us to think holistically about different facets of the city and how they influence the release and uptake of carbon. Much like the human body metabolizes food, Boston can be thought to metabolize carbon, consuming, transforming, and emitting carbon in all aspects of urban life, from urban green spaces to commerce and industry. As part of our urban metabolism research, my colleagues and I are taking direct measurements of the variation in CO2 across the region to understand how carbon moves and is exchanged within different parts of the city. While we don't yet have robust carbon policies on the national or international level, we are using Boston as a testbed to develop the observational and methodological framework that will allow us to verify that carbon reduction and greening goals are actually met. Many cities, including Boston, have taken the lead in reducing CO2 emissions, but this metabolism research will help us move towards verifiable commitments.
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