That Sinking Feeling: Megacities in Decline

Well, not really in decline in the way you’re thinking. Megacities, defined by the United Nations as areas with urban populations in excess of 5 million persons (think Tokyo, New York City, Mumbai), are slowly sinking into the earth – according to research from the Netherlands (and reported by the BBC). Coupled with raising sea levels due to climate change, humanity’s most densely packed population centers at risk of longer and deeper floods.

Sea Level Rise, City Subsidence (via BBC)

Land or the ground sinks into the Earth’s crust naturally, as any geographer will tell you. One method is tectonic plate movement. Depending on the plate, one may be subsumed under another with one being pushed upwards and the other being pushed under. These geologic processes also cause earthquakes and volcanic activity (see: the Pacific Ring of Fire). As the BBC article points out, this geologic activity may be responsible for about 1 mm of subsidence a year. According to the research, a longitudinal study using radar imagery (measuring elevation), concludes that human activity – particularly groundwater extraction – is the primary culprit for city subsidence.

In most cases, a city’s drinking water supply is sourced from local groundwater. As this water is extracted from underground aquifers, one would assume that heavier buildings and infrastructure would press down upon, and compact, the underlying soils. Of course, the relative amount of compaction would be dependent on the local soil (sand, clay, silt, and other factors). While some cities have reduced, if not almost wholly eliminated, municipal subsidence (the article mentions Tokyo and Venice) by halting groundwater extraction – this option isn’t a realistic solution for coastal megacities in less economically advanced countries (Dhaka, Lagos, Jakarta). In these and other “smaller” cities (between 1 and 5 million persons) municipal budgets are already strained coping with a vast informal housing sector (read: slums and shantytowns), a stagnant infrastructure, and poor administration. Adding a requirement for an entirely new source of drinking water for an entire city would be prohibitively expensive.

However, given rising sea levels, municipal subsidence, some 75% of humanity lives on the coast (but not necessarily in a city), and about half of humanity lives in cities (not necessarily on a coast) – we can easily see the scale of the problem. Fortunately, the problem is somewhat long-term, city subsidence and sea level rise occurs at rates of millimeters a year. However, though the number is small the results are disproportionately large. A National Geographic article, published Sep 2013, cited a OSCE report stating that a 20-inch sea level rise would leave 150 million people and $35 trillion dollars (about 9% of global GDP) at risk of coastal flooding. A city sinking 20-inches, an easy analogy, would take 40 years at 5 mm a year.

Of course, this timeline would compress markedly if cities are to contend with both rising sea levels and their own sinking. The timeline is likely to further compress if urban population growth rates remain high as new residents also demand access to water.

Even more long-term, Z Geography wonders if the growth of megacities will lead to their own decline. Could this natural hazard (coastal flooding) combine with other human-made hazards in cities (violent conflict, poverty) and lead to a period of deurbanization in the next 50, or 100, years? One could argue “yes”, in the true spirit of Malthus, but we shall watch for technological and economic innovation – perhaps a cheaper way to reduce our dependence on groundwater?

#AmericanProblems: a Letter to the People of Russia

Dear Friends,

Please accept Z Geography’s most humble apologies for the attitudes of his fellow Anglophones, specifically those that delight in uploading photos of bathrooms, doors, and non-potable water.

Sadly, the first inclination among many of us, being Anglophones, is to immediately point out our infrastructural superiority when we travel to a new and exciting place, especially when that place is associated with a quadrennial and exciting event. I apologize for this.

What makes these attitudes particularly frustrating is the complete lack of empathy.

The World Health Organization, one of several UN organizations tracking the seventh Millennium Development Goal (halving the number of people without access to improved drinking water sources), reported in 2013 (using 2011 data) that 768 million people don’t have access to improved drinking water. And that’s just “improved” drinking water. As our vociferous news correspondents in Sochi will tell you, having an improved drinking water source isn’t necessarily a potable water source. Right now there are more people in the world who don’t have access to clean water than there are people in the United States. One proxy for unclean water is unimproved sanitation (also tracked by the Millennium Development Goals), the same WHO report noted that (in 2011) over 2.5 billion people lacked access to an improved sanitation facility. Of that number, 761 million relied on a public sanitation facility, 693 million use an unimproved sanitation facility (i.e. unclean), and the remaining billion defecated in the open.

This lack of empathy is hardly forgiveable though, considering that we (in the U.S.) are still dealing with our own non-potable water problems.

There isn’t any excuse for the non-thinking masses in Sochi and on Twitter who have, evidently, forgotten all about the 300,000 West Virginians who lost access to clean drinking water when an industrial chemical spilled into their water source. As the New Yorker found, they were told “not to drink the water, cook with it, wash in it, or even use it do laundry.” And the MCMH chemical is LETHAL to humans, or at least – we think so:

“Pretty much all that anyone knows about the health effects of this chemical is what size dose is fatal for rats, and that number comes from a single, non-peer-reviewed study. A crude extrapolation of this number puts the fatal dose for a large adult at a little more than two ounces.” (from the New Yorker)

And then just yesterday (that is 11 February), and again in West Virginia in the same “general area” as last month’s chemical spill, a coal company accidentally released “coal slurry” into a tributary of the Kanawha River. Again, MCMH is one component of the chemical in the slurry. However, as the LA Times reports, state officials say public water intakes were not affected. Last week, the director of Kanawha-Charleston Health Department noted that residents were confused when the state initially indicated the water was safe (following last month’s spill), and then issued safety warnings for pregnant women and re-starting water bottle deliveries.

The director’s family isn’t using tap water, which bears some olfactory signs of containing MCMH (smelling of licorice), and local doctors are advising residents to not drink tap water.

Thus, my friends, kindly disregard the Twits and the “educated” journalists currently infesting your country and remember that there are Anglophones out there who hope that President Putin makes a concerted effort to improve access to clean drinking water for all Russians, regardless of ethnicity, language, or religion.

I wonder if any of the journalists in Sochi are from West Virginia?

Sincerely yours,