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?

Natural Resources: Hidden Curse or Buried Treasure?

Z Geography is out of town this weekend.

A USA Today article (published on 16 January 2014) gushes (no pun intended!) over the continuing development of the Eagle Ford Shale in southern Texas. The article aptly discusses the benefits and problems associated with major natural resource discoveries. Besides the variety of ways physical geography influences natural resources (accessibility, availability, to name a few) human geography also influences (and is influenced by) natural resources.

Over the short term, the article highlights the sudden influx of money into an otherwise struggling, predominantly rural belt in the state of Texas. In an accompanying article, USA Today reports that one county sitting atop the shale had to give $300,000 back to the state last year (under Texas law, more affluent districts return “a percentage” of their revenue in order to fund poorer ones). This year this particular district is projected to return $28 million. This money, derived from a variety of links with the shale’s oil (land royalties, spiking land prices, greater sales), facilitates the district’s acquisition of technology to enrich public school education. In addition, the funds have also allowed for upkeep and maintenance on existing facilities. To illustrate this boom, according to the article 70% of the district’s students qualify for free or reduced-price lunches. Through these oil-generated funds, all 1,300 students in the district of access to new iPads, new school buses, and free school supplies.

Of course, there also a number of short term (and long term) problems associated with this boom. There are the deleterious effects of being located so close to production sites with some residents reporting nose bleeds and head aches, in addition to the terrible smell (described as rotten eggs) as trapped natural gases are burned (flaring). The city of San Antonio has recorded higher-than-normal ozone levels since the drill began, according to the article. In addition to negative health effects, these gases will also contribute to a changing climate. In addition to negative health and environmental effects, there have been other second-order effects. Prostitution and traffic have both increased as “man-camps” of oil workers are established throughout the region. This unforeseen geographic clustering is taxing for small, local police services. The massive (though ultimately temporary) increase in population is also straining regional water supplies and raising concerns of potential contamination of groundwater supplies.

A shale skeptic, quoted in the article, discusses another long term pit fall – the end of the oil. He estimates that, at current extraction rates (which are likely to rise), the Eagle Ford Shale has “five to 10 years” of production. These predictions (as dedicated followers of the “peak oil” debate will know) should be taken with a large grain of salt (or sand). As technology, and prices, change it is impossible to predict (especially with great accuracy) when the end will occur. As the article notes, the technology being employed in shale exploitation has been used for natural gas extraction. The difference came with crude oil reaching $100 a barrel and advances in technology. In short, it became profitable. Despite this a geographically-wider reading of oil economies is useful.

The United Arab Emirates, particularly Dubai, provides one method of preparing for time when oil extraction becomes unprofitable. Dubai has been investing much of it’s profits from oil into becoming a financial hub of the Middle East, in addition to catering to high price tourism. These activities ensure a diversification of the local economy that should endure once physical extraction of natural resources end.

The local and state governments also have a positive role to play, and should. Nigeria is enduring a decades-long insurgency in the Nile Delta where locals accuse the central government of failing to redistribute oil revenues fairly. Then there is the case of the Democratic Republic of Congo where extensive natural resource endowment, and extraction, provides little (or no benefit) to locals thanks to a contracted state, persistent political and social violent instability, and corruption. While southern Texans unlikely to turn violent over the various negative health effects associated with production, local governments (backed by the state government) have the ability to mitigate these effects (if not wholly control them).

Natural resources can contribute to conflict (both violent and nonviolent), identifying places where these conflicts can occur is paramount to the geographer. For a transportation geographer, it may be the identification of critical intersections that are most likely to serve as bottlenecks or prone to traffic accidents. For medical geographers, it may be the delimiting of the extent to which serious health issues may arise, the proximity of people to production activities and prevailing winds. While knowing these, and other, answers are unlikely to solve underlying conflicts that can be used to more cost-effectively target solutions.

Thus, the development of the Eagle Ford Shale is “a gift” to an underdeveloped region of Texas. However, as discussed in the USA Today article and this post, the region faces serious long-term and short-term challenges. Properly managing, administering, natural resources is the corner stone of long term stability.

Super Moon (2013)

This overly short post is dedicated to our constant extraterrestrial companion, the Moon (or Luna). The video below is a NASA science video on the 2011 perigee (super) moon. One key takeaway – if you decide to take a picture try to capture it as it comes over the horizon as it passes common reference points on the ground (such as trees or buildings).

And Happy Belated Summer Solstice! What do these things have to do with Geography? If we’re discussing the entirety of Earth, the perigee (super) full moon of June 2013 represents the closest the moon comes to the Earth in 2013. As the video notes, while natural disasters are unlikely, the effect on tides will be the strongest during the perigee (super) full moon.

The summer solstice occurs when a planet’s semi-minor axis is at its maximum tilt towards its star. In the northern hemisphere of Earth, this translates to the longest (in terms of daylight) day of the year. By the same token the winter solstice, when Earth is tilted at its maximum away from the Sun, is the shortest day of the year.

The Aral Sea, Lakes?

Occasionally, I find myself examining side-by-side shots of the so-called “Aral Sea.” I’m beginning to think that its time to we, as Geographers, Politicians, Academics, and Private Citizens, stop referring to the various Aral Lakes as the “Aral Sea”.

As far as I’m aware, there isn’t a proscribed standard surface area, diameter, radius, or perimeter distinguishing between a lake and a sea. What they have in common is that they are large-ish bodies of water, fresh or salty. A lake is surrounded on all sides by land, while a sea is “definitely marked off by land boundaries” (thanks to This is why we have the Aral Sea, which is completely surrounded by land, and the North Sea, which isn’t. Generally though, seas are larger than lakes.

Compare the two images below, a composite of two satellite images taken in 1989 and 2008, further down is another image (from showing the “Aral Sea” in June 2013. The Earth Snapshot website also provides a link to a Columbia University webspace discussing the “Aral Sea Crisis.”

Aral Sea (1989, left) Four Lakes of Aral (2008, right), via wikipedia.

My point is purely the naming convention. I’m guessing its primarily out of a sense of tradition that we continue to use the term “Aral Sea” for what is clearly three different Aral Lakes. In addition to the tradition of the word, perhaps it is also to assuage our (humanity’s) own guilt. If we continue to refer to this as the Aral Sea I suppose we’re deluding ourselves (since most of us will never see it) into thinking that humans can’t possibly have this sort of affect on our natural environment. According to wikipedia, the Aral Sea had an area of over 26,000 sq. mi. in 1960. In 2004, the “four lakes” (East, West, Middle, North) had a combined area of 6,600 sq. mi.

As it turns out a number of “lakes” are larger than the “Aral Sea”, even when in it was a single body in 1960. Lake Superior (Canada and the U.S.) has a surface area of 31,000 sq. mi. Lake Ladoga (in Russia) the largest lake in Europe is larger than the four lakes of Aral, having a surface area of about 7,000 sq. mi.

Although some would argue that it would be a stretch to think that a simple name would have much impact on the world. I would argue that this name frames and defines (duh) our world and, more importantly, our place in it. Sure, we may continue to use “Aral Sea”  out of hope that the Aral Sea will make a come back, but at the moment, it feels delusional. If not delusional, then it might just be a denial. A denial to the potential fact that we, humans, wrecked our environment.

The EOsnap’s image (taken in June 2013) below shows the four lakes of Aral in the upper right. The vast expanse of water on the left is the Caspian Sea.

Four lakes of Aral (2013), via