The paper illustrates different urban environments with different heights and densities. Credit: npj Sustainable Urban Development (2021). DOI: 10.1038/s42949-021-00034-wResearchers from CU Boulder have published a study showing that low-rise, high density environments such as those in Paris are the best urban forms to reduce greenhouse gas emissions throughout their entire life span.This work was published in the journal Urban Sustainability and was done in partnership by Edinburgh Napier University. The built environment contributes significantly to global energy demand, carbon emissions, resource consumption, and waste generation. It is responsible for 39% of all greenhouse gases emissions in the United States, and 50% of all materials extracted and 42% final energy consumption in the European Union. This makes it an area of great interest for research and improvement on climate change.Jay Arehart, a paper author and an instructor in the Department of Civil, Environmental and Architectural Engineering, stated that the paper challenges the current understanding that cities of tomorrow must be densely packed and stretch upwards. This is to reduce greenhouse gas emissions. The idea behind tall buildings is to maximize space, reduce energy consumption, and allow more people to be accommodated on each square meter of land.Arehart stated that both the urban sprawl in the suburbs and the high-rises in New York City are not optimal. We showed that new developments should not only reduce the carbon emissions from buildings' operations, but also minimize their whole-life cycle. While density is necessary for an increasing urban population, height is not.Four different urban typologies were examined by the team, from dense-and tall to sparsely-and-low. They then created 5,000 simulations based on real world data in order to determine their lifecycle greenhouse gas emissions. Francesco Pomponi (lead author and professor at Edinburgh Napier University) said that this approach took into account both premium for land (the additional land required to build low-rise buildings compared with high-rise), and premium for height. This was done to allow for fair comparisons.Pomponi stated that he developed a new urban density metric in order to accurately measure the city's growth. Our results showed that density is needed to support a growing urban population. However, height is not. It seems that the world will need more Parises, but fewer Manhattans. I still love New York in the coming decades.Urban Sustainability is the latest addition to the Nature Partner Journals Series.Francesco Pomponi and colleagues, Decoupling density (from tallness) in analysing cities' life cycle greenhouse gas emissions, npj Urban Sustainability (2021). Francesco Pomponi and colleagues, Decoupling density of tallness in analysing city's life cycle greenhouse gas emissions, (2021). DOI: 10.1038/s42949-021-00034-w