CityReads│Seeing Our Urbanizing Planet Like Satellites

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Seeing Our Urbanizing Planet Like Satellites

Satellite images reveal cities unseen by naked eyes.

Seto, Karen C., and Meredith Reba. City Unseen: NewVisions of an Urban Planet. Yale University Press, 2018.

Sources: https://time.com/longform/infrared-images-city-unseen/

https://yalebooks.yale.edu/book/9780300221695/city-unseen

Sometimes, it takes a bit of perspective to see the bigger picture. That is the tack Karen C. Seto and Meredith Reba of Yale University take in their new book, City Unseen: New Visions of an Urban Planet. The two authors use satellite images of 100 cities around the globe to showcase the intricacies of the relationship between urban settlements and the natural world.

You may have visited the cities that appear in this book. You may even live in one. And yet many of these images show scenes unlike anything that you or I have ever seen. These images present the city at an unusual scale—one that highlights how humanity and the planet work together orin opposition. We see urban areas shining in unexpected colors—casting even the most familiar places in an almost other worldly light to reveal a better understanding of vegetation, water, and human settlements. A change of perspective has made familiar places on Earth suddenly seem foreign and reshaped my understanding of our home planet.

New global impacts require new perspectives

The age and location of the world’s oldest city are upfor debate. But one thing is uncontested: cities have played a central role in the evolution of human civilization for thousands of years. Historically, the availability and types of resources in surrounding hinterlands limited the sizeand scope of a city. Water, fuel for energy, and building materials restricteda city’s growth.

The physical geography—including vegetation, soils, landforms, topography, and climate—also shaped the social and economic characteristics of cities, determining how quickly cities grew, their patternsof expansion, building styles and construction materials, and even how much time urban dwellers spent outside.

Today, trade, commerce, and migration have decoupled cities from their immediate surroundings. Cities rely on both the local and global environments. Global supply chains bring resources from distant sources tourban centers. Migrant workers bring new labor and transform the cultural composition of even the most diverse cities. In the other direction, urban influence expands outward. Cities are not only regional hubs of production and innovation, but also global engines of growth, with economic and political effects on places and people far away. The environmental impacts of urban areas are also global. Urbanization has affected wildlife habitat and biodiversity, the global demand for energy, and greenhouse gas emissions and climate change. Cities today affect and are affected by the state of the entire planet.

It took from the beginning of human history to 1960 for the global urban population to reach one billion. It took another twenty-six years—until 1986—to reach two billion. Today, the global urban population is increasing by one billion roughly every thirteen years. Onereason why urban populations are increasing at a faster rate than before isthat increasingly, population growth is occurring mainly in urban areas

To understand urban growth, however, we must look at both the population and the resources required to build, transform, and operate our cities. Every day, an area equal to 20,000 American football fields becomes part of the global urban landscape. Cities consume more than 75 percent of the world’s primary energy. Cities and their built environments are literally transforming landscapes, reshaping landforms, vegetation, waterways, and regional microclimates. Our urbanizing planet is a story about human ingenuity, resolve, and perseverance. Given that we will add another two to three billion urban dwellers to our planet by the end of the century, it is critical that we have a broader perspective of cities.

Seeing cities like satellites

Today, we have whole new means of seeing, studying, and understanding these complex connections between the urban environment and the world through data from satellites. Since the launch of Google Earth in 2001, satellite images of Earth have become easily accessible to the public.Many of us can see the most remote areas of the world with a single click, instunning detail, even on the screens of our mobile devices. Satellite data provide new perspectives on the pulse of humanity, and nowhere is this more evident than in urban settlements. This book takes advantage of these data to provide new perspectives on humanity’s urban imprint and to tell the story ofthe city’s rise.

Although the statistics about contemporary urbanization show unprecedented magnitude and pace of change, the view from space also showsus that urban areas take up a small fraction of our planet and that there is incredible diversity in an urbanizing humanity. We see that an urbanizing planet is composed of towns, villages, and other metropolitan regions of varyingsizes and shapes. Urbanization today is not just about dense settlements and tall skyscrapers. Many urban dwellers around the world live in settlements that are relatively small in size—with several thousand inhabitants— challenging our preconceived notions of the city.

The images in this book situate urban areas in their larger environment. Our wider perspective shows cities as a critical driver of environmental, social, and economic change outside of city limits, and allows readers to consider cities as interconnected to their regional and global hinterlands. At the same time, we must never forget that cities must also be understood at the human level.

Satellites offer several perspectives impossible fromunaided eyes. In some images in this book, we show repeat observations of thesame place. These allow us to observe urban areas over time. What spatial patterns emerge as cities grow or shrink? How is the city changing in responseto its environs and vice versa? How do changes in season and climate affect the urban landscape?

The images in this book also appear in unexpected colors. These alien landscapes are the result of a type of translation—are-creation of light outside the visible spectrum in colors our eyes can see. Just as dogs can hear sounds inaudible to humans, sensors aboard satellites areable to “see” what our eyes cannot. These wavelengths unseen by our eyes help us explore the health of vegetation, the water content of soils, the heat emanating from a concrete surface or the pollutants in the atmosphere. These other wavelengths help us explore the health of vegetation, the water contentof soils, the heat emanating from a concrete surface or the pollutants in the atmosphere. Seeing in different frequencies can provide an advantage; butterflies use markings visible only in the ultraviolet (UV) spectrum to gauge the health of their potential mates; some birds use the UV reflectance in the skin of baby chicks to adjust feeding strategies; and for many fish, UV vision is essential for for aging and mate selection.

Satellite sensors extend our vision into these frequencies and allow us to see the health of vegetation and the distribution of heat across a city, as well as urban attributes such as the types of materials used in buildings and roads. We also see the unexpected beauty of these urban centers and their surrounding landscapes— visible only from above.

Finally, the overhead perspective of satellite imagery offers a new context and thus new understandings. We see geometries of transport, diversity of forms, angularity and sinuosity of the urban settlements. We also see that, despite the contemporary trends and scale of urbanization, urban areas are relatively small globally but impactful.

The book is organized into three sections that provide a narrative arc of an urbanizing planet. It begins with “Earth’s Terrains,”which showcases urban areas situated in their larger natural landscapes. In this section, we see cities defined by their physical environments such as mountains, rivers, and agrarian landscapes. In the second section, “Urban Imprints,” we see the physical expression of urbanization. Cities and their supporting infrastructure such as roads, urban design, and night lights leave tangible, material impressions on the planet. In the third section, “Transforming the Planet,” we focus on how the demand for urban resources is changing landscapes, and how adynamic earth is changing urban vulnerabilities.

Urbanization is a permanent change to the surface ofEarth. Urban sustainability will be a prerequisite for planetary sustainability, not only because that’s where most people live, but because that’s also where the demand for the planet’s resources—water, food, energy—comes from. Cities are vulnerable to many things—climate change, extreme weather events, lack of social cohesion, economic disruption. But cities are also extremely productive places that are rich in ideas, innovation, and culture.

The widespread availability of remote sensing data from satellites orbiting the earth has allowed us to see our planet from new perspectives and enabled new understandings of the relationship between cities and the environment. Contemporary large-scale and rapid urbanization is transforming the planet, and the availability of big data from Earth-observing satellites is transforming how we study these changes. Many of the most pressing sustainable developmentand environmental challenges have an essential urban component for their solution.

We need this knowledge not for one or even a dozen cities, but for all urban areas worldwide—small or large, developing or established, industrialized or industrializing. Remote sensing imagery can be a central element in developing this new urban science. 

With the right satellite image and analysis, the angularity of streetscapes in Detroit, Mich., become apparent to us; we are able to detect differences in street structures and building materials between the border cities of Mexicali in Mexico and Calexico in the United States; geological folds called anticlines and synclines in the oil and gas-rich region of Chongqing, China, are revealed; we can even “see” air pollution over Beijing,etc.

The US-Mexico border snakes across this image, about athird of the way down. It divides the twin cities of Calexico, California(population 40,000) from Mexicali, Mexico (690,000), both visible in purple.Above the border, blocks are neatly arranged with a smaller urban footprint;below, Mexicali sprawls into a mosaic of surrounding agricultural plots.

Chongqing, China, straddles three horizontal “grooves”in the Earth’s crust known as anticlines and synclines. The city is built on sandstone in a region that’s well-known for coal mining.

The Russian town of Semikarakorsk (population 24,000)is surrounded by a patchwork of farmland, showing the diversity of crops grown in the region. It’s an area Anton Chekhov once described as so fertile you could poke a stick into the ground and it would take root. The Don river, which snakes past the city, brings nutrients to the fields in good years, and catastrophic flooding in bad ones.

Malé, Maldives 1:32,000 The Republic of Maldives, with an average elevation of just under 8 feet, was the first country to sign theKyoto Protocol committing to reduce greenhouse gas emissions that cause climate change. A recent study found that many atoll islands are threatened not only bysea-level rise, but also flooding, which will negatively impact freshwater availability and may render these low-lying places uninhabitable by the middle of next century.

Arequipa, Peru 1:325,000 Mina Cerro Verde is an open-pit copper and molybdenum mine shown in blue in the bottom left of the image, just south of the city. The mine, which has a symbiotic relationship with the city, has been expanded in recent years and operates the city’s first wastewater treatment plant

Seoul, Republic of Korea 1:148,000 Twenty-seven bridges span the Han River in the center of Seoul (pictured in dark blue), stitching together the two halves of the city and acting as networks between communities on opposite sides of the river

Osh, Kyrgyzstan 1:175,000 Rectangular crops, producing tobacco, grains, cotton and melon occupy the Alay foothills to the north of the city. The varying colors of the fields highlight the variety of crops and growth stages, while fallow fields are pictured in purple

Zaatari, Jordan 1:25,000 Home to about 80,000 Syrian refugees, Zaatari is the largest refugee camp in the Middle East, now functioning as an informal city for its residents. Globally, the number of displaced people reached an unprecedented record in 2015, exceeding 65 million,more than the populations of Canada, Australia and New Zealand combined.

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