According to the recent Summary for Urban Policymakers of the IPCC’s sixth assessment report, today urban areas house about 1/2 of the human population, generate 2/3 of its economic output, and are responsible for about 3/4 of global carbon emissions. The fraction of humans that live in urban areas is also growing rapidly. These basic facts make clear that the key challenge for future sustainability is supporting the positive aspects of urban development for human welfare while reducing the impact of cities on the global environment and climate.
To navigate these issues, it is important to adopt an approach that recognizes urban societies as systems and acknowledges that their properties are not simple sums of their parts. Consider this thought experiment. There is an island of 10,000 square kilometers, where 100,000 people need to live in a sustainable way, with no inputs from beyond the island’s shores. How should the people be arranged? One option is for the people to be spread out with a constant density across the island, and the other is to clump them into a mix of towns and rural areas of varying density. Which arrangement would require less total energy? And which would support higher living standards? It should be obvious that the clumpy pattern is better, in that it would reduce the average distance between people. This would reduce the time and energy spent moving around and increase rates of social interchange, enabling a more extensive division of labor. In addition, resources are typically distributed in clumpy ways, such that it is more efficient for people to distribute themselves with respect to these resources and associated land uses. However, while the clumpy pattern may be more productive and efficient overall, it can also facilitate unsustainable exploitation of the island’s resources if people are too shortsighted regarding their actions.
This simple exercise demonstrates that cities are both problems and solutions for climate adaptation, and as a result there is a pressing need to understand the fundamentals of how urban systems work and what their aggregate, long-term effects are for people and the environment. These are exactly the sorts of questions that the archaeological record is well-suited to study. But importantly, reconstructing the detailed histories of specific urban societies will not be very helpful here because, in detail, nothing ever happens twice. What is needed instead is an effort to build understandings that provide greater predictability regarding the long-term effects of changes in specific properties across urban systems. This is the goal of the emerging field of urban science, to which archaeologists are beginning to contribute.
In a recent paper in Nature Urban Sustainability, a group of urban scientists and sustainability scientists, including several archaeologists, teamed up to propose a transdisciplinary effort that seeks to generate actionable research on urban adaptation that recognizes the nature of cities as social networks embedded in physical space. For archaeologists, the point is not necessarily to generate actionable findings directly or solely from archaeological evidence, but for archaeological evidence to contribute to a general understanding of urban systems that can in turn suggest specific actions by which urban societies can adjust, change, and transform their energy systems, economies, infrastructures, support systems, interactions, and governance mechanisms to mitigate the adverse effects of climate change.
The next assessment cycle of the IPCC will focus on urban climate adaptation, so now is the time for archaeologists to engage with efforts like this one and produce studies that contribute to a more just and sustainable future. There is an audience for this sort of work. Let’s do it together!