That proportion has continued to rise steadily, reaching 55% as of 2018. It's climbed faster in China, up from 48% to 59% — meaning an additional 180 million people are living in Chinese cities.
China now has 130 cities of at least 1 million people, more than the U.S. (45), European Union (36) and South America (46) combined.
Carbon choices determine US cities committed to futures below sea level
Authors:
Strauss et al
Abstract:
Anthropogenic carbon emissions lock in long-term sea-level rise that greatly exceeds projections for this century, posing profound challenges for coastal development and cultural legacies. Analysis based on previously published relationships linking emissions to warming and warming to rise indicates that unabated carbon emissions up to the year 2100 would commit an eventual global sea-level rise of 4.3–9.9 m. Based on detailed topographic and population data, local high tide lines, and regional long-term sea-level commitment for different carbon emissions and ice sheet stability scenarios, we compute the current population living on endangered land at municipal, state, and national levels within the United States. For unabated climate change, we find that land that is home to more than 20 million people is implicated and is widely distributed among different states and coasts. The total area includes 1,185–1,825 municipalities where land that is home to more than half of the current population would be affected, among them at least 21 cities exceeding 100,000 residents. Under aggressive carbon cuts, more than half of these municipalities would avoid this commitment if the West Antarctic Ice Sheet remains stable. Similarly, more than half of the US population-weighted area under threat could be spared. We provide lists of implicated cities and state populations for different emissions scenarios and with and without a certain collapse of the West Antarctic Ice Sheet. Although past anthropogenic emissions already have caused sea-level commitment that will force coastal cities to adapt, future emissions will determine which areas we can continue to occupy or may have to abandon.
Transportation experts say car-congested cities could become a thing of the past, provided people are prepared to ride-share with a robot driver.
A study published Thursday by the Paris-based Organization for Economic Cooperation and Development suggests that widespread use of "taxibots" could cut by 90 percent the number of cars needed to perform the same number of journeys per day.
Researchers used data from Lisbon, Portugal, to simulate how such self-driving, communal cabs would affect traffic. Even with only one passenger per ride and no complementary public transport, the number of cars still dropped by 77 percent.
Despite notable differences in appearance and governance, ancient human settlements function in much the same way as modern cities, according to new findings by researchers at the Santa Fe Institute and the University of Colorado Boulder.
Previous research has shown that as modern cities grow in population, so do their efficiencies and productivity. A city's population outpaces its development of urban infrastructure, for example, and its production of goods and services outpaces its population. What's more, these patterns exhibit a surprising degree of mathematical regularity and predictability, a phenomenon called "urban scaling."
But has this always been the case?
SFI Professor Luis Bettencourt researches urban dynamics as a lead investigator of SFI's Cities, Scaling, and Sustainability research program. When he gave a talk in 2013 on urban scaling theory, Scott Ortman, now an assistant professor in the Department of Anthropology at CU Boulder and a former Institute Omidyar Fellow, noted that the trends Bettencourt described were not particular to modern times. Their discussion prompted a research project on the effects of city size through history.
To test their ideas, the team examined archaeological data from the Basin of Mexico (what is now Mexico City and nearby regions). In the 1960s -- before Mexico City's population exploded -- surveyors examined all its ancient settlements, spanning 2000 years and four cultural eras in pre-contact Mesoamerica.
Using this data, the research team analyzed the dimensions of hundreds of ancient temples and thousands of ancient houses to estimate populations and densities, size and construction rates of monuments and buildings, and intensity of site use.
That humans and the cities we build affect the ecosystem and even drive some evolutionary change in species' traits is already known. The signs are small but striking: Spiders in cities are getting bigger and salmon in rivers smaller; birds in urban areas are growing tamer and bolder, outcompeting their country cousins.
What's new is that these evolutionary changes are happening much more quickly than previously thought, and have potential impacts on ecosystem function on a contemporary scale. Not in the distant future, that is -- but now.
A new paper by Marina Alberti of the University of Washington College of Built Environments' Urban Ecology Research Lab published this month in the journal Trends in Ecology & Evolution suggests that if human-driven evolutionary change affects the functioning of ecosystems -- as evidence is showing -- it "may have significant implications for ecological and human well-being."
Alberti, a professor of urban design and planning, said that until recently it was assumed that evolutionary change would take too long to affect ecological processes quite so immediately. Such thinking has prevented evidence from coming together "in a way that can only emerge through a cross-disciplinary lens," she said, observing the interactions between humans and natural processes.
"We now have evidence that there is rapid evolution. These changes may affect the state of the environment now. This is what's called eco-evolutionary feedback.
"Cities are not simply affecting biodiversity by reducing the number and variety of species that live in urban habitats," Alberti said. Humans in cities are causing organisms to undergo accelerated evolutionary changes "that have effects on ecosystem functions such as biodiversity, nutrient cycling, seed dispersal, detoxification, food production and ultimately on human health and well-being."
It's a feature of the landscape one sees throughout China. On the sides of roads, at the edges of construction sites, on the steep banks of rivers, and in pastures that wrap around the fat pylons of future highways, Chinese people are farming, tilling tiny jewel-like plots that may only last a season, or rushing a herd of goats or a flock of ducks through traffic.
As its leaders often remind the world, China has 22 percent of the world's population, but less than 10 percent of its arable land (as much as one fifth of which, it was recently reported, is severely polluted). People find ways to make up for the shortfall. For centuries officials have complained of peasants cultivating marginal lands, and for just as long Chinese farmers have been geniuses of agricultural improvisation, making use of whatever land they could find when they needed it.
Today, the country is in the midst of a massive shift from countryside to city. Much of it has occurred at will, as ambitious migrants have left the fields to seek new jobs and new experiences in the factories of China's booming cities. But many others do not move at will. Instead, they are expelled from their homes and into strange new lives as city folk as the fields they once tended give way to new roads and shopping malls or slip under the rising waters of newly risen dams. Still others fall somewhere in between. They may find themselves following their children to new lives and new status as members of an urban population that, for the first time, in 2011 exceeded the number of those remaining in the countryside. China's leaders hope that 70 percent of the country will be urban by 2030.
In cities, old rhythms of life die hard, and even as more and more farmland on the outskirts of urban areas disappears, new transplants and old holdouts continue to find patches of ground to plant.
Tim Franco, a Shanghai-based photographer, has spent time on these "microfarms" in the heart of the megacity Chongqing, where the changes underway across the country appear especially stark. Some farmers grow food to feed their families, others to supplement their incomes, and some because, with the city closing in all around them, it's the only thing that makes them feel at home.
ON MAY 21st China’s finance ministry released details of a new scheme to allow ten wealthy localities in China—Shanghai, Beijing and Guangdong among them—to issue bonds directly for the first time in two decades. Although a small pilot scheme has allowed a few cities and provinces to issue bonds in the past, in practice the federal government issued them on their behalf. So the new scheme of municipal bonds is a radical departure.
The shift comes as China’s leaders increasingly fret about the mountains of local debt that have built up despite the restrictions put in place 20 years ago. Back then party leaders in Beijing were concerned about how recklessly municipal governments were borrowing. Local leaders had binged on bonds and bank lending to such an extent that a crisis loomed. Fed up with the resultant scandals and excesses, the federal government decided to solve the problem by banning local borrowing.
Ancient Urban Ecology Reconstructed from Archaeozoological Remains of Small Mammals in the Near East
Authors:
Weissbord et al
Abstract:
Modern rapidly expanding cities generate intricate patterns of species diversity owing to immense complexity in urban spatial structure and current growth trajectories. We propose to identify and uncouple the drivers that give rise to these patterns by looking at the effect of urbanism on species diversity over a previously unexplored long temporal frame that covers early developments in urbanism. To provide this historical perspective we analyzed archaeozoological remains of small mammals from ancient urban and rural sites in the Near East from the 2nd to the 1st millennium BCE, and compared them to observations from modern urban areas. Our data show that ancient urban assemblages consistently comprised two main taxa (Mus musculus domesticus and Crocidura sp.), whereas assemblages of contemporaneous rural sites were significantly richer. Low species diversity also characterizes high-density core areas of modern cities, suggesting that similar ecological drivers have continued to operate in urban areas despite the vast growth in their size and population densities, as well as in the complexity of their technologies and social organization. Research in urban ecology has tended to emphasize the relatively high species diversity observed in low-density areas located on the outskirts of cities, where open and vegetated patches are abundant. The fact that over several millennia urban evolution did not significantly alter species diversity suggests that low diversity is an attribute of densely-populated settlements. The possibility that high diversity in peripheral urban areas arose only recently as a short-term phenomenon in urban ecology merits further research based on long-term data.
