Megacity Musings

Greetings from Tokyo, the world’s largest megacity and urban wonderland! With a population of 37.9 million, Tokyo is a place where people appear almost anywhere and everywhere. Despite the high population density, Tokyo remains a fine city to visit. It is nearing the end of winter here and plum blossoms (Prunus spp.) are in sight around the city. Plum and cherry trees are charismatic flagship species that many people within and outside Japan relate to. As pointed out by Professor Evans, the choice of trees planted reflects the country’s or city’s cultural identity. In Tokyo, these beautiful trees are often cultivated in traditional Japanese gardens within shrines and temple grounds, as well as in parks, but are less common along streets, possibly due to their high susceptibility to disease and maintenance requirements. Nevertheless, plum and cherry trees continue to be the country’s favourite angiosperms.


Plum blossoms are celebrated at Yushima Tenman-gū Shrine during the annual spring festival

Besides plum trees, Ginkgo trees are also popular among the Japanese. Ginkgo biloba is the “Tree of Tokyo”, but is an exotic species introduced to Japan’s urban landscape in the late 19th century. Referring to Weng Ngai’s post on street trees, I agree that representing a city with native trees is ideal but may not be the most practical option. For instance, Ginkgo was chosen as a street tree over other native trees for its fast maturity and ability to withstand urban conditions in devastated Japanese cities after the 1923 Great Kanto Earthquake and World War II. The changing appearance of Ginkgo marks the progress of seasons and people have been able to relate to this exotic species more than other natives like the Japanese Elm.

As Weng Ngai suggested, the trees that are planted in cities depend on the preference of different stakeholders, which is closely tied to the function of trees. Although Ginkgo is the “Tree of Tokyo”, it is not prevalent everywhere. Along wide roads and high-speed expressways managed by public corporations, the species assemblage comprises mainly of Japanese red pine, black pine and cedar, with Ginkgo only contributing one-tenth, because the evergreens are better at reducing traffic noise in surrounding residential areas. Nevertheless, exotic species like Ginkgo continue to complement geometrical Japanese landscapes and remain deeply rooted in the lives of the Japanese. At this point I was wondering if Singapore has a national tree… We have a few iconic ones such as Tembusu and Angsana, but do Singaporeans relate to them as much as they relate cherry trees to Japan?


Defoliated Ginkgo trees in the University of Tokyo campus

City planners and dwellers seemed to have developed this mindset that cities should be neat, clean, and orderly. Perhaps evolutionary psychology theories may explain this? As a city modernises, there becomes a stronger preference for orderliness in a dynamic urban landscape. The belief that orderly environments lead to improved mental health, life satisfaction, better thinking, tradition and convention may be a form of psychological adaptation in a rapidly changing urban environment.

Beyond the urban sprawl, the majestic Mount Fuji is visible. The mountainous region around this composite volcano is dominated by an endless sea of low-rise earthquake-resistant dwellings. Tranquility, clean water and fertile soil are just a few reasons why people would prefer to reside near the volcano rather than the urban core. Would you live near Mount Fuji?


Mount Fuji beyond the urban sprawl

Out of the 37.9 million people in Tokyo, I am probably one of the few people who goes around looking at urban lithophytes that grow spontaneously in Tokyo’s urban environment.

Plantago sp.

Plantago sp. growing at base of concrete wall

Covered in the recent lecture on spontaneous vegetation, urban lithophytes are plants that grow on rocky, hard and exposed surfaces with limited nitrogen substrates. They are not only adapted to a low nutrient substrate, but also to limited water availability and frequent direct sunlight. In urban areas, the roots of these plants penetrate into the crevices to tap on available nutrients in rainwater, litter, moss, dead tissues, and soluble alkali salts that leach from concrete and mortar. Dispersed by wind or urban birds, urban lithophytes may be considered “weeds” to some people, but to others these plants are valued for their medicinal properties and may be deliberately planted in gardens (or in labs, as in the case of Cannabis). If you find these plants interesting (I hope so), please feel free to check out my website on the urban lithophyte flora of buildings in Singapore.

Now for some urban wildlife. Have you seen a domesticated Japanese macaque?




Well, now you have.

This Macaca fuscata was performing at the Yushima Tenman-gū Shrine in Tokyo. I was baffled to see the monkey being tied up, made to jump across hurdles, balance on balls and form gestures to the crowd. Even though I was impressed by the macaque’s intelligence and skills, I preferred very much to watch it foraging in the wild near Lake Kawaguchi.


There was hardly any food for this wild macaque in winter, and it tried very hard to invade buildings in the vicinity but to no avail. It ended up feeding on the branches and bark of trees.

This post can go on forever, but I shall end here with a Japanese white-eye (Zosterops japonicus) resting on a plum tree. Amidst the fast-paced and highly developed urban environment, one can still find amazing flora and fauna in the city of Tokyo. Do visit when you can!


The science of correlation

Ecologists are obsessed with correlative science, urban ecologists even more so. We realize that most natural systems are infinitely complex and cannot be comprehended from a purely mechanistic perspective. One may model protein folding by quantifying the forces of hydrophobic interactions, dipole moments, bond-angle strains, etc., but one cannot exhaustively describe the probability of reproductive success in a generation of Javan Mynahs in Orchard road by a systematic evaluation of every possible (direct) cause to fecundity and mortality. Most natural systems involve too many abstract components to be studied in a thoroughly experimental manner. But that does not mean we surrender to ignorance. Urban ecology (and social sciences in general) emphasizes a pragmatic approach to science that makes logical speculations from generalizable trends. Correlation science is science. …But it is not without problems…and I’ve found myself asking them many times over the last half a sem while studying urban eco.

I cite the recently mentioned example of street trees not as criticism, but in order to incite a more personally-relevant inquiry into the subject. Prof Evans mentioned several times that physiological constraints are the (main?) reason for the high number of exotic trees planted in Singapore. I must qualify before commenting that (i) I do not believe the statement is wrong; the ‘correlation’ does exist (ii) I do not assume Prof speaks presumptuously—I’m most certain he is perfectly well-informed concerning the myriad of other forces that act concurrently and historically to shape the ‘community composition’ of Singapore’s streetscapes. Notwithstanding, the statement is extremely difficult to swallow as it is. Is the fact of “large proportion of exotics in streetscape community” simply explainable by “physiological constraints—Singapore no savannahs, our native trees not adapted”? Many tangents we could pursue. I state a few briefly:

  1. Historic and economic factors. It was only just recently mentioned (was it in a 4265 or 4262 lecture?) that, historically, many plant stocks have simply been more available to streetscape managers than others. Many of these species were discovered and popularized by botanists and arborists who had not been sampling the globe unbiasly (is it coincidence that Hevea brasiliensis, Swietenia macrophylla, and Albizia saman, some of the earliest introduced tree species (1876) are all neotropical?). Certain tree species are simply better studied and “marketed” than others, and very few of these are native to our island for obvious reasons. Tree planting patterns have evolved over the years in Singapore, and most of us have actually observed it in our lifetimes. But the progress of this evolution does not seem to have followed the botanical/horticultural discoveries of more physiologically-adapted tree species as tightly as we would have thought to be the case if physiology were the main/dominant predictor of native/exotic tree community composition. Streetscape managers do shopping too…which brings us to the next factor.
  2. Psychology. It might be discounted anywhere else in the world, but not in Singapore. Because streetscape is managed by relatively few individuals, polarization in “preferences” really make a difference in our streetscape community assemblage. I dare say confidently that Prof Tan from the Botany lab (an individual—individuals should never be “factors” in ecology right?) has probably had more statistically significant influence on the evolution of NParks tree planting philosophy than a good number of other factors we might think of including in any ‘urban tree community model’. And I think many of us can testify to a slight (subconscious?) bias towards foreign imports in this country, which NParks officers might have shared (in the past?) as well. Put another way, the mere idiosyncrasies of an individual streetscape manager ARE going to make a significant difference in our tree community assemblage—how do we harmonize that with the physiological argument? and how do we go about making science out of this?
  3. Lastly, there are actually many native species that grow very well in streets but aren’t commonly planted. Even a dim-witted undergrad like I can name ten or more without looking up a reference book. Singapore was not completely rainforest ecosystem—coastal forests contributed many street tree species and can contribute potentially many more (the SSS1207 textbook discusses this). The Figs are a very good example. Benjamina, microcarpa, kerkhovenii, superba, virens… Thoroughly native, many considered RF spp. They can and do grow well in the urban environment, yet they are not planted much along roads for practical reasons—they damage structure, they have crazy girths, they make scary pillar roots, they shed frustrating volumes of fruits, and their many religious associations can be problematic. Some native tree species which were once extensively used are now being phased out because of practical considerations as well (and perhaps also because we have more money to splurge on other more flamboyant exotic species). Think Cerbera odollam and Terminalia catappa, a 5min thought exercise might reveal why. The argument that Alstonias, Szygiums, Artocarpuses cannot do well in the urban environment is simply groundless because these do grow by road sides in urban environments local and beyond. The fact that exotic savannah tree species offer a wider selection and perhaps additional safeguard against dessication is valid, but one cannot help but realize that the non-biological factors still trump the physiology argument.

What, then, is the point in saying all of this? My question is not about street trees; it is about urban ecology and the science of correlation. The argument from physiology is not wrong at all. Physiological demands place a ‘cut off criterion’ which eliminates quite a few native tree species from the candidature, consequently giving exotic savannah species a much higher chance of being fielded in this game. Yet in the science of infinitely complex systems, explaining a “top 15 trees in cities” histogram with “physiology” may be a slight oversimplification. How far can we extrapolate biologically valid arguments like this one before sounding more like politicians than scientists? Again, I do not propound that Prof Evans is teaching us stuff that is wrong or even inaccurate; and in fact I believe the method of the single take home message is pedagogically powerful. But putting classroom time behind us, is it most rigorously scientific to state the “physiology explanation” without a balanced qualification of the (extremely) strong, confounding (and potentially interacting) effects of the (many) other components of this system?

Or, notated, is

Native/Exotic spp in Tree Community ~ Physiology + etc

a scientifically valid simplification of

N/E.STC ~ HistoricalFactors + EconomicFactors + PracticalConsiderations + IndividualPreferences + Physiology + EF^2 + HF:EF + PC:Phy + EF:Phy + EH:PC + IP:Phy + etc


Lightscape Map Desired

Although I would not call myself an avid astronomy enthusiast, I enjoy stargazing in my free time, albeit with no telescope and via the naked eye. Hence, last week’s topic about light pollution in urban areas really intrigued me. Often, when the situation allows it, I enjoy pointing out stars and constellations to my friends. This often happens on campus, together with a clear, cloudless sky. (The exact location would be the stretch of road from Faculty of Science to NUH, near the School of Medcine) There, I would easily point out to them, the bright and more easily recognizable constellations like Orion. When the sky is really cloud free, it is even possible to see the Plaeides star cluster! Usually my friends would be amazed and I would chide them for not looking up at the skies more often. However, most would say that they were never able to see these near their homes which contradict with my own experience, for when stargazing at locations near my house, I was always able to see and recognize constellations such as Leo, Canis Major, Scorpio, just naming a few. In fact, in my opinion, the night sky there and here in NUS does not differ that much. That said, my friends live pretty far away from me, them living in the Jurong area while I stay in the Serangoon area, though we all live in HDB estates. Since an attempt to dig up a lightscape-map of sorts of Singapore did not have any results, it makes me wonder about how does light pollution vary in the different areas of Singapore? Does this correlates to the urban geometry of that area? If so how is it correlated?