climate change sustainability

What’s the world’s least sustainable city?

Have you ever wondered, out of curiosity, what the least sustainable city on earth might be? In writing his book about sustainable cities, Professor Andrew Ross of New York University didn’t go looking for good examples. He wanted to document the worst he could find, because if that place could transition to a sustainable future, then it would be it be possible anywhere. The book is called Bird on Fire, and the city is Phoenix, Arizona.

hohokamPhoenix has an interesting story, because the city that stands in the Sonoran desert today is not the first settlement to be built there. The Hohokam people were there first. Uniquely among North American tribes, they were canal builders, and built a large network of canals and weirs to irrigate their notoriously dry homeland. In the Middle Ages, these canals allowed the Hohokam to settle, farm, build sizeable towns, and establish trade routes with their neighbours.

The project did not last. The population grew and began to strain at the ecological capacity of the region. A series of droughts made things worse, while floods upstream destroyed vital parts of the canal network. By 1400 the Hohokam had abandoned the land and their adobe walls eroded back into the desert. The ruins of their largest town can be visited at Casa Grande National Park.

The original canals were rediscovered in the 1860s, and pioneers dug them out again. Knowing that they were building on the ruins of an ancient predecessor, the early residents chose the name Phoenix. It was at first a small farming town, then became a trading post with the arrival of the railway. New dam projects increased its water supply and made new growth possible, and in 1912 it became the state capital.

In 1947 an unfortunate incident occurred which had serious repercussions. There was a fire at the streetcar depot. Most of the fleet was destroyed, and rather than build a new public transport system to replace it, the city decided to focus on cars instead. Streets were widened, suburbs were built without tram connections, and the scene was set for urban sprawl.

Drawn by the year-round sunshine, those suburbs continued to grow. In more recent years, new housing developments have been the main source of growth in the city. The cotton fields and citrus orchards that used to be important have been turned over to development and the sprawl now covers well over a thousand square miles. Population has boomed, growing by a quarter in ten years. Predictably, the city suffered particularly badly from the sub-prime housing crisis.

phoenixToday greater Phoenix has a population of 4.3 million people, but it’s still in the middle of the desert. That desert is very slowly getting hotter and drier as the climate changes. The city depends on water pumped 300 miles from the Colorado River, which is itself depleted by overuse and long term drought. Besides the obvious challenges of water, Phoenix has very high CO2 emissions and notorious air quality. It also has a staunchly anti-green political culture. It’s hard to say if it’s absolutely the least sustainable city on the planet, but it’s certainly a contender.

It would be easy to condemn Phoenix as an environmental lost cause. It probably shouldn’t have been built in the first place, and the existence of a ruined civilization on the same spot should have been a warning rather than an invitation. But it’s not as if 4.3 million people can just be moved and the place bulldozed, so the question of transitioning Phoenix to a sustainable footing has to be seriously examined. It’s not really good enough to say it can’t be done.

Nobody needs to examine that question more than Phoenix itself, and the signs are pretty mixed. A ‘Re-invent Phoenix‘ scheme is re-orienting development along light rail corridors, although I note that it is still a growth strategy. Water conservation measures have reduced per capita consumption by 20% over the last two decades, but those savings have been entirely overtaken by the growing population. You’d have thought solar energy and particularly solar thermal ought to be a no-brainer in the Valley of the Sun, but apparently the city’s stated renewable energy target is a pathetic 15% of electricity generation by 2025.

There is huge potential for infill development on abandoned lots and brownfield sites, creating a denser city – something Detroit has tried. Building codes are being improved to encourage walking and cycling, and there are many opportunities for urban farming too. In one of the more interesting developments, the Gila River Indian Community won a court case that granted them a third of the city’s Colorado river rights, and they are using the water resource to raise local food production.

I would need further convincing before declaring that Phoenix could ever be made sustainable, starting with a dramatic change in political culture and public awareness of environmental issues. But I do respect Andrew Ross’s sentiment in studying the city: “We don’t just live in the success stories”, he says. “Much more vulnerable and even recalcitrant cities have much more to teach us about whether we have the wherewithal to make changes.”


  1. Although it may not be apparent, Perth, despite being visually a much wetter city than Phoenix, is even less sustainable.

    This is due to two factors. The first is the unique nature of Australian soils. In most present-day landmasses, the Alpine Orogeny and large-scale Quaternary ice sheets are continually producing new soil. In contrast, Australia lies upon the thickest and densest crust in the world, so that no orogenies have occurred since the formation of Gondwana in the Carboniferous (BEFORE the dinosaurs). Moreover, its separation from Antarctica has left Australia much too hot to have its Palaeozoic-age soils scoured by ice sheets. For your information a limited paleopedological record shows that even in the Miocene (eight million years ago) Europe and North America had soils analogous to Australian soils, revealing that Australian soils are in fact THE geological norm and that familiar European and North American soils constitute exceptional geological rarities.

    The consequence of this complete absence of new soil formation are:

    1) uniquely low nutrient concentrations, most critically of the chalcophile elements like copper, zinc and selenium necessary to catabolise photosynthesis
    2) uniquely deep soil texture contrasts due to high levels of leaching of clay from topsoil, resulting in high erosion hazards even on flat land
    3) uniquely high bulk densities making Australian soils very difficult to work and producing very difficult rooting
    4) uniquely low nutrient retention ability leading to severe pollution from fertiliser use
    5) uniquely large supply of flat land relative to population that provides no economic efficiency for careful land use or soil conservation
    6) uniquely low runoff coefficients due to the prevalence of “cluster” (proteoid) roots to absorb minimal concentrations of phosphate and other essential nutrients. For an idea, Perth with a mean rainfall pre-AGW of 900 millimetres produces less runoff than Phoenix with a mean rainfall of about 200 millimetres but much younger and richer soils.
    7) uniquely high precipitation elasticity of runoff. In even the most elastic regions of the northern and western hemispheres, elasticities rarely exceed 3, whereas in southern Australia they frequent exceed 5 (i.e. a 10 percent change in rainfall produces a 50 percent change in runoff)

    The second thing is that anthropogenic global warming has produced more radical changes in climate in Western Australian than anywhere else on Earth. Since 1973, rainfall in southwestern Western Australia has declined by one-third vis-à-vis natural averages, whilst in the areas of Western Australia east of the 119th meridian it has increased by over forty percent. Critically, the absence of annual growth rings or useful coral cores means we cannot verify the extremely likely scenario that these changes are utterly unprecedented over the Quaternary. Nonetheless, they have already virtually eliminated runoff into Perth’s dams. Between 1882 and 1974 the average was around 275,000 acre-feet; since 2010 it has been only 45,000 acre-feet; in contrast 431,000 acre-feet of water flowed into Perth’s dams in July 1946 alone. The consequence has been that Perth – despite momentarily retaining its green forested look – has become a true desert city dependent like Gulf States cities on desalination in a zero-runoff environment.

    Efforts to improve public transit and develop renewable energy in Perth have been if anything less bad than in the rest of Australia though still utterly woeful. The low cost of land and high demand for housing have produced a worst of both worlds scenario in Australia – unaffordable housing and dreadfully unsustainable development. Transport planning, rather than aiming to totally eliminate unsustainable, energy-intensive car and air transport in favour of 100 percent investment in high-speed rail, absolute road building bans and developing new housing to exist entirely free from private motorised transport, continues to build new freeways and plans new airports. Electricity policy in sun-drenched Perth has been equally terrible – despite tremendous potential, the abundance of coal has meant virtually no investment in solar and wind power that could easily have powered the city. At the same time – in a landmass whose mammals have a fifth the basal metabolic rate of European mammals – there has been no effort to design houses to use a fifth or a tenth the energy as such an ecology would dictate. My personal experience, though, clearly shows that with better quality building Australia could almost certainly design its housing to use a fraction the present energy consumption on the increasing number of hot days.

    1. Interesting. Soil formation is a fascinating science, and doesn’t get as much as it deserves when it comes to sustainability. Thanks for taking the time to explain Perth’s precarious situation.

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