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総合政策研究 第 21 号（2013.3） 51

The Use of Greenery to Combat Urban Warming in

Brian HARRISON

Abstract Urban warming is primarily due to the covering of natural land and vegetation by roads and buildings. Because of that, one of the countermeasures used for mitigation is to employ greenery. This paper discusses the reasons behind urban warming in Tokyo and the process of greenification.

they contain is converted into water vapour). The Key Words resultant built-up area then absorbs more of the environmental studies, heat islands, Japa- sun’s heat than does the natural land, thus aggra- nese studies vating the situation. The effect is also amplified at Contents night; heat which is stored in the roads and The situation in Tokyo buildings is gradually released and raises night- Green areas in Tokyo time temperatures. Green roofs In order to feel more comfortable in the higher Green spaces temperatures, people make greater use of air- Green walls conditioning in their homes, offices and cars. The Green curtains air-conditioning may make the indoor tempera- Conclusion tures lower, but the heat is then emitted out- doors, further worsening the outdoor situation. In Urban warming, often termed the heat island central city areas, the vicious circle is further en- phenomenon, refers to the effect when the tem- hanced in the presence of large buildings which, peratures of the central areas of a city are higher besides absorbing heat, prevent the heat escap- than in the surrounding rural areas. This is analo- ing both due to the existence of heat canyons gous to an ‘island’ of heat being present in an area (with the large buildings trapping the heated air of lower temperatures. in the deep ‘canyons’ between the buildings) and Heat islands are formed when the natural land also the blocking of possible cooling winds. in a city is lost due to the construction of roads, It should be noted that this urban warming is buildings and car parks etc. The disappearance of distinct from global warming; while the two may the natural land results in the loss of the cooling share certain characteristics and mutually rein- effects of soil and vegetation due to shading and force each other, their essential causes are differ- evapotranspiration (a process whereby heat is ab- ent. sorbed from the air by plants when the water 52

17 6 16.5 Average 5 16 temp. 15.5 4 Days >35C 15 3 14.5 2 14 1 13.5 13 0

1900 1920 1940 1960 1980 2000 1963 1971 1979 1987 1995 2003 2011 Figure 1 Changes in the average Tokyo temperature Figure 2 Days over 35 oCinTokyo (shown as a 5-year (oC) during the 20th century running average) (Data from Meteorological Agency) (Data from Japan Meteorological Agency)

The situation in Tokyo into the past; for example, the value for a five- a) Temperature year average for 2012 cannot be calculated until In the course of the 20th century, global tem- the data for 2014 is available．］ peratures increased by an average of 0.6 oC, a phe- The number of ‘midsummer days’ (defined in nomenon referred to as global warming; in Japan as being days on which the temperature Japan, the average increase was approximately exceeds 30 oC) has increased substantially. This is 1 oC. (Mikami 2005 a : 8, 9 ; Tokyo Environment conveyed quite dramatically in a visual manner Bureau, date unknown) In Tokyo, however, the by two often-published thermal images originally rise in temperature during the same period was a released by the Environment Ministry. With much greater 3 oC(Figure 1) ; the additional in- deep red indicating days over 30 oCandlighter crease can probably be attributed to the heat colours for days with lower temperatures, an island effect．［It should be noted that, unless oth- image of the Tokyo area for 1999 is mostly dark erwise stated, the original source of all tempera- red and orange, whereas the corresponding im- ture data referred to or used for calculations in age for 1981 consists mostly of pale colours. (To- this paper is the Japan Meteorological Agency, kyo Environment Bureau, date unknown). It is JMA e.g. JMA 2012］． not only the number of hot days that is increas- Besides the rise in average temperatures, ing; the number of hours over 30 oCisalsorising. there has been a significant increase in the abso- In 1980, the numbers of hours over 30 oCwas 168, lute number of hot days, especially very hot days. but this had increased to 357 in 2000, and in 2004 The number of days with temperatures above reached nearly 500 hours. (Mikami 2005 a : 8-11) 35 oChasincreased significantly, as shown by the Although there have been considerable in- five-year running averages (Figure 2)．［Five-year creases in daytime temperatures, nighttime tem- averages are an average for a particular year peratures have actually shown double the plus both the two preceding years and two subse- increase. In Tokyo, this can be seen clearly in the quent years. This helps to smooth out the distort- number of nettaiya, or so-called tropical nights: ing effect of an exceptional year e.g. a much hot- nights during which the temperature fails to fall ter or cooler year. It also necessarily means that below 25oC. The five-year running average for the year referred to is always at least 2 or 3 years the number of tropical nights in Tokyo shows a HARRISON :TheUseofGreenery to Combat Urban Warming in Tokyo 53

50 higher temperatures, the distribution of heat is 40 not even. In Tokyo itself, the highest tempera- tures tend to be focused in the northwest wards, 30 >25C especially -ku. In the Kanto plain as a 20 whole, the hottest spots are to the north, often in 10 Gunma and (e.g. , which regis- 0 tered the joint highest official temperature ever recorded in Japan ~ 40.9 oConAugust 16th, 2007).

1902 1916 1930 1944 1958 1972 1986 2000 (JMA 2007) Figure 3 Number of tropical nights (熱帯夜) in Tokyo The reason is directly connected with the heat (shown as a 5-year running average) (Data from Japan Meteorological Agency) island effect. The heat that has built up and been absorbed by the concrete and asphalt of the large and steady increase over the 20th century buildings and roads during the day is slowly re- (Figure 3). The number of such nights in the early leased during the night, producing the feeling of part of the century was very low, and had risen heat ‘hanging’ in the air. This results in the excep- to 14 in 1963, 35 in 2000, 41 in 2004, and 56 in 2010. tionally warm nights. On summer days, the pre- What might be termed “superhot” nights, in vailing winds tend to blow from the south and which the temperature does not drop below 27oC, southeast; thus the hotter air over Tokyo in the used to be extremely rare, but are now becoming morning is blown towards the north and north- relatively common. In the summer of 2007, there west, adding to the heat that builds up for other were no less than 10 such nights, including the reasons (e.g. the sun’s strong rays, the effect of hottest-ever recorded night, during which the which is perhaps amplified by areas situated in temperature remained all night in excess of 30 oC. basins, as well as the effect of being inland from Although large areas of Tokyo suffer from the the coast). At night, though, due to the greater

Table 1 No. of days over 30 oCand no. of tropical nights for Tokyo and Kumagaya (Data from Japan Meteorological Agency)

Year Days over 35oCTropical nights Tokyo Kumagaya Tokyo Kumagaya 2003 0 7 17 1 2004 6 28 41 13 2005 4 14 31 12 2006 3 10 20 9 2007 7 21 31 10 2008 1 13 25 15 2009 0 4 20 3 2010 13 41 56 30 2011 3 23 45 15 2012 6 32 49 14 54 area of natural unpaved land, the areas in the sur- hence a benefit for global warming; however, in rounding prefectures cool down more than cen- Tokyo this is not the case since the period of tral Tokyo, with not so much stored heat to be maximum electricity consumption occurs in sum- re-radiated nocturnally from roads and buildings. mer, not winter, with the widespread use of air- As a result places such as Kumagaya have many conditioning. more extremely hot days than Tokyo, but con- versely have a much smaller number of tropical b) Health effects nights. (Table 1) (Mikami 2005 c: 42 ; Moriyama The high temperatures can have various 2004 : 34-35) A place such as Hachioji, a city health effects, ranging from sleep disturbance which is situated in an inland basin to the west of through to heat stroke and death. One objective Tokyo but which does not receive the same de- approach to gauge the general trend is to exam- gree of Tokyo’s nighttime heat due to its location ine the numbers of people taken to hospital be- relative to the centre, shows temperature pat- cause of heat stroke. The 5-year running aver- terns intermediate to those of Tokyo and Kuma- ages for such people in Tokyo show a dramatic gaya. and continuing increase; before 2007, the abso- The buildings can have a further effect on tem- lute values had never reached a total of 1,000 for peratures. In various parts of central Tokyo, the whole summer (defined as the three-month there are relatively high concentrations of high- period from July to September), yet in August rise buildings. The heat which is absorbed by the 2007 alone the figure topped this value. (Tokyo buildings has no means of escape, and the tem- Fire Department 2007) perature is thus further raised by the ‘heat can- There seems little doubt that the rise in people yons’. Additionally, the buildings can block the carried to hospital because of heat stroke is cooling winds from Tokyo Bay; such an effect directly related to the higher temperatures. was clearly visible following the rapid redevelop- There is a strong correlation between the num- ment of certain central areas e.g. and ber of heat stroke victims and both the numbers Shiodome Shiosaito. (Mikami 2005 d: 58-61) of days and also hours during which the tempera- There is perhaps a natural tendency with ture exceeds 30 oC. (Murayama 2005) It seems urban warming to focus on the higher tempera- likely that the tropical nights, which cause poor tures recorded during the summer; however, sleeps, hinder the body’s attempts to recover the heat island effect is not limited to any particu- from the stress of surviving the greater number lar season. Indeed, the largest changes are ob- of extremely hot days, thus making people more served in winter, with minimum temperatures in susceptible to heat stroke. Also, it must be re- Tokyo rising by 5oCinthe last century. (Mikami membered that the ‘victims’ of the heat are not 2005 a : 11) This can have serious consequences just limited to those who collapse with heat since it allows the expansion of populations of in- stroke; many others suffer lesser symptoms, and sects etc. which would normally be killed off by large numbers of people will suffer poor sleeps at the freezing temperatures, thereby potentially night. disturbing ecosystems. From the energy point of view, it might be thought that the milder winters c) Rainfall would mean less consumption of fossil fuels and Before the 1990s, Tokyo experienced some HARRISON :TheUseofGreenery to Combat Urban Warming in Tokyo 55 heavy downpours but they were not regular is the existence of ozone in the lower reaches of events. Since then, though, there has been a sig- the atmosphere. At 40 oC, ozone is produced at nificant increase in the number of such down- ten times the rate which occurs at 30 oC. The pours, which often fall within relatively limited higher temperatures which are being recorded areas. could thus undoubtedly lead to higher concentra- In Japan ‘heavy’ rain is defined as rain falling tions of ozone and hence increases in photochemi- at more than 10 mm/hour, and ‘torrential’ rain as cal smog, even though perhaps not all the blame rain in excess of 50 mm/hour. Apart from ty- can be attributed to the heat island effect. Cer- phoons and rainy season fronts, torrential rain tainly in recent years there has been a rise in was extremely rare before the 1990s, but now ozone levels in Tokyo. Figures for show a occurs with some regularity. This intensive local- direct correlation between the temperature and ized rain is believed to be caused primarily by the the number of days on which smog alerts are is- heat island effect. In recent years, the rain has sued; when temperatures exceed 37 oC, there is a also been falling later in the day (evening rather greater than 80% probability of an official smog than afternoon), which is believed to be due to an alert. (Kajii 2005). expanded heat island effect plus the effects of global warming. Green areas in Tokyo The mechanism is believed to be as follows. As The major cause of the heat island effect in To- the city becomes warmer during the hot summer kyo has been the destruction of natural land cover, days, the hot air rises. This air is then replaced by which has perhaps occurred to a greater extent cooler air moving in laterally, causing winds. As than in other cities. Let us consider the reasons the hot air rises, it cools and forms clouds. With for this and what the situation is today. the high temperatures, this process tends to occur rather quickly, with the result that when At the end of the Second World War, much of rain begins to fall, it is heavy and falls in limited Tokyo lay in ruins. Reconstruction plans called areas. forextensive greenery, including parks, play- On occasions the amounts of rain involved can grounds, large avenues and broad green belts. be quite staggering. For example, on July 21st However, these plans failed to come to fruition. 1999, a day in which there was neither a typhoon The severe financial situation meant that there nor a rainy season front, in just one hour no less were insufficient funds for the purchase of the than 131 mm of rain fell in central Tokyo in what land, and the later resumption of rapid urban was at that time a new record for Japan. (Mikami growth resulted in strong pressure to develop 2005 b: 14) Not surprisingly, such heavy rainfall the land. The planning system that was in force can overwhelm the ability of drainage systems to allowed only weak powers for restricting the de- handle the water, raising the possibility of velopment in designated areas unless the land damage - or even deaths should people become wasactually purchased. The authority which trapped in the flooded basements of buildings. could have enforced simple administration orders to block development on the urban fringes was d) Pollution the Home Ministry (which controlled the police); One of the main causes of photochemical smog however, the Home Ministry, which had been a 56 powerful moral and administrative force prior to speculation led to major land price inflation. This the war, had been disbanded, and the national forced people wishing to purchase residential government (and especially the police) had lost land to look at locations away from the central ar- moral authority due to the events of the war, and eas of Tokyo in order to find affordable sites. In was no longer in a position to enforce those ad- these areas, the new city planning system that ministrative orders. (Sorenson 2002 : 159-162) was introduced in 1968 was ineffective at pre- The original plan had envisaged green corri- serving land for public uses such as parks. The dors in the inner areas of Tokyo, with a strictly result was the rapid spread of unplanned urban controlled green belt to remain as farmland (part- sprawl. (Sorenson 2002 : 229-231) In order to ly reflecting contemporary thinking in the United exert a degree of control over the development, Kingdom, and partly to maintain some self- the government designated areas as Urbaniza- sufficiency in food). One aim was to prevent a tion Promotion Areas (UPAs). However, both recurrence of the pre-war high population den- farming interests and the Ministry of Construc- sity in central areas, with people instead living in tion had an interest in maximizing the designa- a number of satellite towns. However, the plans tion of such areas, with the result that they were failed; Sorenson identifies three reasons which over-designated. (Sorenson 2002 : 232-234) The he believes were probably the most critical. 1968 plan envisaged all land in the new UPAs be- Firstly, there was a lack of funds (substantial ing taxed based on market value assessments. finances were necessary but there were compet- However, the farming community was able to ing demands from many areas of Japan which persuade LDP politicians to insert clauses in the had also suffered considerable destruction). Sec- laws which provided loopholes whereby almost ondly, there were opposition movements e.g. all farmland was given preferential tax treat- against non-compensated expropriation, a prob- ment, with taxes often coming to merely 1~2% of lem perhaps made worse due to the lack of prior the taxes levied on adjacent residential property. public consultation. Thirdly, the plans were prob- (Sorenson 2002 : 233-234) Sorenson states that ably very unrealistic; compared to other cities, this was one of the best examples of “the LDP plans for Tokyo were the most idealistic but the rewarding one of its core client groups at the least actually achieved. There was considerable expense of the public interest”. (Sorenson 2002 : pressure for quick construction, although road- 235) widening plans etc. need time for negotiations. This unfair tax situation unsurprisingly caused (Sorenson 2002 : 162-167) friction with local residents. In 1992 the law was As a consequence, the plans to make Tokyo a reformed, and owners of farmland were only very green city tended to come to nothing, with allowed to maintain their tax privileges if they construction in both the inner and outer areas agreed not to develop their land for the next 30 proceeding in a rather haphazard manner. The years; if they wanted to develop their land, they decrease in green land continued over many had to pay higher tax. In Tokyo nearly half years. For instance, between 1972 and 1995, it fell decided to forego development and have their from over 1400 km2 to 1300 km2. (Ojima 2002 : land designated as “productive green land” (sei- 109) san ryokuchi); in surrounding areas, the percent- One reason for the decrease was that land age was much lower (Saitama 24%, Kanagawa HARRISON :TheUseofGreenery to Combat Urban Warming in Tokyo 57

23%, 19.3%). (Sorenson 2002 : 235) green roofs, green walls and green curtains. Let From the tax and fairness point of view, the us now consider these approaches in general, and lower tax rates for farmland were patently un- examine the situation in Tokyo specifically. fair. However, when viewed from the viewpoint of the heat island phenomenon, the existence of Green roofs large numbers of plots of natural land cover was Green roofs are layers of vegetation which lie beneficial. Conversely, the 1992 revisions of the on top of a building’s conventional roof surface. law meant that a considerable number of plots They are often classified into ‘intensive’ and ‘ex- would be developed, thus potentially worsening tensive’ roofs, referring to the amount and type of the heat island effects. In many cases farmland vegetation used and hence the amount of mainte- wascovered by asphalt to provide small car nance required. In recent years, most interest has parks. Unfortunately this was very detrimental focused on extensive green roofs, which are rela- to combating the heat island effects, and it must tively lightweight and easy to deal with, needing be wondered whether there is not a way to pro- relatively little maintenance and resource inputs. vide financial incentives to convert such land They can easily be incorporated into new build- back to its natural state. ings or added to existing buildings. (Green Roof With all the pressures for development, Tokyo Centre) ended up with far less green space than exists in many of the world’s major cities. Cities such as a) Green roofs in general London, New York, Berlin and Vancouver all The International Green Roof Association have in excess of 25 m2 of green park area per (IGRA) lists various benefits of green roofs be- resident. In contrast, the average value for the sides the mitigation of the heat island effect, and whole of Japan in 2002 was approximately 8 m2/ classifies them into public and private benefits. person. Within Japan, the Tokyo metropolitan The public benefits, i.e. benefits for the environ- area ranks a lowly 42nd out of the 47 prefectures ment and society, generally include the following. at only 6.8 m2/person, with the so-called “tokubet- Firstly, the roofs help to maintain biodiversity by suku”(central wards) ranking bottom of the 13 acting as a natural habitat for animals and plants; specially designated cities (with an average area besides being lively places in themselves, they of only 3.1 m2/person). (Aichi University of Educa- can “connect isolated refuges for flora and fauna tion 2007) within sterile city centres” for e.g. bees, birds, Although there are a number of countermea- butterflies and beetles. Secondly, they can help to sures that can be used to combat urban warming, prevent localized flooding because of their ability because the primary cause of heat islands is the to retain stormwater (it is possible to reduce the loss of natural green land cover, it is not surpris- amount of immediate run-off by up to 60-90%). ing that one of the key approaches to mitigating Thirdly, they have an anti-pollution function in the problems is to increase the amount of green- that they can remove dust and harmful chemicals ery in inner urban areas. Since it is of course not from the air, leading to decreased particulate con- easy to increase the amount of green parks, ef- centrations and less smog. Furthermore, by forts have tended to focus on other means of improving city landscapes, they can provide greenification, specifically the construction of benefits to people’s psychological and physical 58 health. (IGRA) additional requirements. (Toshi Ryokka Gijutsu The IGRA also lists a range of private benefits Kaihatsu Kikō 2006) Tokyo became a leader in Ja- for those who have green roofs. Firstly, the roofs pan in this field; in the absence of national legal have a longer life (which can be doubled due to restrictions, various other authorities imple- the protection afforded to the actual roof of the mented similar regulations, but rather later e.g. building). Secondly, they lower noise levels (sound introduced a requirement for reflection can be reduced by 3 dB, and insulation greening rooftops over 3,000 m2 in 2005, followed can be up to 8 dB better). Thirdly, they provide by restrictions on roofs larger than 1,000 m2 in thermal insulation (which results in reduced Osaka and Hyogo prefectures in 2006 and in energy use and heating costs in winter). They prefecture in 2007. (Kankyō Gijutsu Jōhō also provide a heat shield (indoor temperatures Nettowāku 2007) are reduced in summer, which means less energy When the goals for the Tokyo ordinance were use and thus air-conditioning costs). Finally, being established (in 1998), the 5-year running av- green roofs allow greater space which can be erage for the number of tropical nights in Tokyo used for a multitude of purposes. (IGRA) was 30.4, and by the following year had risen to 32.4 nights. The goal stipulated in the ordinance b) Green roofs nationally and in Tokyo was to reduce this 5-year average to a total of 20 The Tokyo government passed an ordinance nights per year by the year 2015. (TMG 2001) which took effect in April 2001 and stated that for Although the metropolitan government did not all new or renovated buildings with an area ex- itself directly offer subsides for the construction ceeding 1,000 m2 (or 250 m2 in the case of public of green roofs, there was a foundation for this facilities) at least 20% of the usable roof area must purpose (Tōkyōto Toshi Ryokka Kikin) as well as be green. From the following year, with the aim other sources of support, including an increasing of strengthening the regulation and accelerating amount of aid from local government. (TMG, date the greening of roofs etc., an amendment to the unknown) Of the Tokyo wards, Chuo-ku (1989) ordinance stipulated that companies submit plans and Kita-ku (1994) have long offered financial aid for greenification, and drew up penalties for non- but most others began in 2002 (-ku, compliance. (TMG, Tokyo Metropolitan Govern- Shinagawa-ku, -ku) or 2003 (Taito-ku, ment 2001) This constituted part of Governor Minato-ku, Chiyoda-ku, Sumida-ku, Koto-ku). Shintaro Ishihara’s plan to increase the total Some did not start until 2005 (-ku, Nerima green area in central Tokyo from 29% to 32% by -ku, -ku); Bunkyo-ku aimed at 2006. 2015. (Metropolis 2003) (Toshi Ryokka Gijutsu Kaihatsu Kikō 2006) In a According to an urban greenery website, the revision to the law for the preservation of urban Tokyo regulations in principle required the green areas, private facilities in the areas spe- greening of at least 20% of the land minus the cially designated as being important green building area, and at least 20% of the roof area to spaces, which were mainly in the central areas of which people had access or could be used; the large cities, were (if plans for the facilities were so area covered by building support materials could approved by the local wards or cities) able to be included in the total. Various wards and cities receive preferential tax treatment. (TMG 2001) within metropolitan Tokyo also implemented On the national front, the annual rate of con- HARRISON :TheUseofGreenery to Combat Urban Warming in Tokyo 59

struction of green roofs rose steadily, doubling c) Uses of green roofs in Tokyo from approximately 13.5 hectares in 2000 to The primary purpose of constructing green about 25.5 ha in 2006, with approximately 5,900 roofs is, of course, the mitigation of the heat is- roofs providing a total green roof area of 160 ha. land effect. However, when green roofs are made, (MLIT 2007 : 2) Nevertheless, the Ministry of they can be used for a multitude of purposes. Be- Land, Infrastructure and Transport (MLIT) ex- low are some of the applications for which they pressed some concern over the fact that, for the are being used in Japan. first time, in 2006 the area constructed decreased Rooftop gardens can, like residential gardens slightly from the year before, although it recog- or parks, be used for relaxation. Such gardens nized that the total number of constructions re- have been constructed on the roofs of govern- mained at around 1000, and that large projects ment buildings e.g. the building housing the head- might have influenced the figures. (MLIT 2007 : quarters of the Ministry of Land, Infrastructure 10). and Transport (MLIT 2002 : 40) and the Taito-ku When the Tokyo regulations were being ward office. (Taito-ku ward office, date unknown) agreed, Japan placed well down internationally in In Ichigaya, Tokyo, a factory roof belonging to the average area of green roofs, although the the Dainippon Insatsu company is used by 1,000 number of actual green roofs was competitive; people per day to relaxaswellasactingasa this no doubt reflects the smaller building size in short cut across the factory complex. (Nikkei terms of area. (Ojima 2002 : 110). Ākitekuchua 2003 : 151) In Kawagoe (Saitama) a The area of green roofs constructed in Tokyo green roof also acts as a pleasant view for work- in the period 2000-2006 was 77.38 hectares; this ers eating in the company cafeteria of a factory. figure includes 29.38 hectares of green areas (Kodansha Editoriaru 2006 : 129-131) A further above ground but which are not on the roof. possible function of a rooftop could be as an exer- (TMG 2007 a) On the other hand, the MLIT gives cise area e.g. on a large roof it might be possible the Tokyo figure for 2000-2006 as 55.42 hectares to construct a running track. Such approaches (MLIT 2007 : 2) ; the reason for the discrepancy are particularly appropriate for large roofs such is not clear. The MLIT states that the figure for as may occur on factory roofs or other large Tokyo represents approximately 1/3 of the total buildings; for instance, green roofs have been for the whole of Japan (34.6%), far above the next- constructed on the roofs of airport terminal roofs placed prefecture (Kanagawa at 18.59 hectares)． at Schiphol airport in Amsterdam (Beatley 2000 : ［These are then followed by Aichi at 12.87 ha and 208) and Vienna airport. The relatively low costs Osaka at 11.25 ha］.Tokyo again clearly outstrips mean that green roofs can easily be constructed other prefectures when the construction totals on public housing projects e.g. a rooftop biotope are expressed in other forms e.g. in terms of area was made on suchaproject in Nishi Tokyo. (Nik- per million of population (Tokyo is over double kei Ākitekuchua 2003 : 92-95) that of second-placed Kanagawa) or area per In hospitals roof gardens could provide a dou- square kilometer within the city planning ble benefit. Besides offering a spot for relaxation, boundaries (Tokyo is over triple the value of Ka- there are potential therapeutic benefits. A classic nagawa, and overwhelmingly more than other research paper reported how patients who had prefectures). (MLIT 2007 : 11). undergone gall bladder surgery recovered more 60 quickly (as well as needing less pain medication) act as a focal spot for communal activities involv- when their rooms overlooked greenery. (Ulrich ing local children, such as taue rice planting and 1984) It is often more difficult to offer such views festivals, in an area conspicuously lacking in in urban environments, but this can now be done green. In Minato-ku, about 100 kg of sweet pota- with green roofs. St. Luke’s Hospital in Tokyo toes were cultivated relatively easily in an experi- built such a garden for its patients to enjoy when ment on top of the NTT building, with the person carrying out some renovation work. (Earth in charge suggesting that similar projects might Pledge 2005 : 56-57) In Japan it is accepted that be suitable for school roofs (where they could no gardens can have a positive psychological and doubt additionally serve an educational function). physiological effect on people in old-age care fa- (Asahi Shinbun 2006) The roofs of large depart- cilities. (Toshi Ryokka Gijutsu Kaihatsu Kikō ment buildings can be used for a similar purpose 2003 : 34-35) e.g. Ruminas Musashi Koganei in Koganei. (MLIT The psychological benefits of green roofs are 2002 : 41). In Osaka, a herb garden and turfed not restricted to those who can walk amongst the area at the OCAT (Osaka CityAirTerminal) build- greenery as the roofs can greatly improve the ing are used for wedding receptions. (MLIT 2002 : visual quality of the urban landscape. Workers in 41) surrounding higher buildings can look down on Perhaps the most well-known green roof in Ja- the green roofs and gain the feeling of overlook- pan is not in Tokyo but in in Kyushu. It ing green fields; the benefit is not imaginary, as belongs to the ACROS building (standing for research has shown that workers in buildings “Asia crossroads over the sea”). It is situated adja- with green features tend to exhibit lower absen- cent to a central park, the only one in the area. teeism and greater productivity. (Beatley 2000 : On the park side of the building, a series of vege- 206-208) tated terraces climb from ground level to the top Department stores could build roof gardens of the building. The effect of the building facade and offer them as a place for customers to relax is to effectively double the area of apparent during breaks in shopping, and perhaps even es- parkland; the feeling of being in an oasis of na- tablish coffee shops. Besides adding to the relax- ture is enhanced by water jets connecting a ing atmosphere, the coffee shops could provide series of pools to produce a waterfall that masks an additional source of revenue for the store. the sounds of the city. (Earth Pledge 2005 : 60-61) Takashimaya department store in Denenchofu, Aconcrete and glass structure juts out of the Tokyo, offers paths to stroll around, as well as central part of the green terraces. Thermocam- fountains and ponds (which further enhance the eras show that the temperature difference be- cooling objectives of the green roof). tween the concrete and grass can be as much as Green roofs also offer the possibility of small- 7oC. (Nikkei Ākitekuchua 2003 : 123) scale agriculture in the manner of urban allot- ment gardens. For example, in the large complex Green spaces of Roppongi Hills in central Tokyo, one roof in- The vast majority of elementary, junior and cludes a small traditional rice paddy and vegeta- senior high schools in Japan have playgrounds ble plot. Besides providing edible produce, the which completely lack grass. As part of the coun- garden can act as a community centre e.g. it can termeasures for combating urban warming, in HARRISON :TheUseofGreenery to Combat Urban Warming in Tokyo 61

2005 a project was carried out to lay turf on the Green walls school grounds of a number of public schools in Green walls are walls on which living plants Tokyo (27 elementary and junior high public provide a cladding system. Traditionally in vari- schools, and 6 metropolitan schools). (TMG 2007 ous parts of the world, climbing plants such as b) The program was extended from 2007, not ivy have grown on external walls, but today high- only for combating urban warming but also to im- tensile steel cables etc. are allowing the approach prove the educational experience for the children. to also be used on tall buildings. Research in this The programme in 2007 called for the provision area has been particularly focused in Germany of 2 billion yen in subsidies to be used for turfing over the last 20 years, with the aim of seeing 70 school grounds (either fully or partially) for plants as integral to the design concept instead of areas exceeding 250 m2 (the funds also being being merely add-ons. (Livingroofs.org) available for greening roofs and walls in addition Besides the visual attraction, green walls also to the grounds). (TMG 2007 b) The cooling cre- provide public benefits in that they help to re- ated by the laying of turf can be considerable. In duce the heat island effect; can remove heavy a test conducted at one school in August 2005, metals, volatile organic compounds and other pol- the difference in temperature between a grass lutants from the atmosphere; cut noise levels; surface and a conventional gravel-type play- and increase biodiversity. Similarly there are a ground was 8.3 oC. It was claimed that the addi- range of private benefits. They can provide shad- tional benefits of turfing were that more children ing which can reduce the daily temperature fluc- played outdoors; safety was improved; there tuation by up to 50% and lessen heating during wasapositive psychological effect on the chil- summer; evergreen plants can also provide insu- dren; the learning environment was natural; lation in winter. Green walls can also lead to pro- and there was an increase in community spirit tection against the weather e.g. heavy rain and (e.g. by parents helping with ground mainte- hail. (Livingroofs.org) nance). (Tokyo Environment Bureau 2007) Green walls can be constructed at various loca- It is also possible to make places greener by tions on a building, and most often involve a type planting trees etc., but sometimes there can be of vine (almost 80% of the total). The most com- unforeseen consequences. For example, in an at- mon location (57.1%) is literally the growth of tempt to increase the amount of greenery in greenery at various heights on the side of the -ku in Tokyo, trees were transported building e.g. Ginza Gallery Center (MLIT 2002 : from Kyushu. However, the soil which was 42). This is followed by growing greenery planted attached to the trees contained larvae of a type of at the base of the building, which can then grow cicada which previously existed in Kyushu but upwards (25.1%). Next comes the downward not in Tokyo. Able to survive in the milder tem- growth of greenery from the top edge of the peratures existing in central Tokyo due to the building (9.4%) e.g. Yakult headquarters building heat island effect, the alien species of Kyushu (MLIT 2002 : 42), and from individual verandas cicada then displaced the smaller type native to and balconies (2.5%). (MLIT 2007 : 7) Tokyo, thereby disturbing the existing ecosys- In 2000, the rate of construction of green walls tem. (NHK 2007) was slow, but as time progressed the rate of con- struction rose rapidly, such that the area of green 62 walls in 2006 (3.6 ha) was approximately 15 times wall and the net; often the net may slope out- what it had been in 2000. (MLIT 2007 : 6). The wards. The curtain produces a cooling effect rate of construction rose especially in 2005 and partly because of shading and partly due to eva- 2006, with the area constructed in 2006 amount- potranspiration. ing to a full 14.2% of the total. (MLIT 2007 : 14). Green curtains can be very effective for There was a big discrepancy in the activities of schools which lack air-conditioning. At one ele- the various prefectures. Again, Tokyo was the mentary school in Itabashi-ku in Tokyo (Itabashi major contributor, accounting for over 40% of the No. 7 elementary school) a green curtain has been total (41.3%) ; this was followed by the prefec- grown along the building façade during the sum- tures of Hyogo (16.5%) and Aichi (13.8%). The mer. The temperature reductions indoors are sig- next places were occupied by other prefectures nificant (temperatures inside the classroom were in the Kanto region (Kanagawa 5.4% ; Saitama reduced from 40 oCto34oC).Itmight be thought 5.0% ; and Chiba 2.8%). The MLIT registered its that the green curtains could make the class- displeasure, though, at the fact that several pre- rooms rather dark, but by growing plants such as fectures had only a few green walls constructed ivy, the sunlight can filter through the curtain, during this time period, and complained that cer- maintaining brightness inside the classroom tain prefectures failed to submit details of any while reducing the temperature. (Itabashi ward construction. (MLIT 2007 : 6). office, date unknown) Green walls have appeared in a number of loca- The green curtains can grow fairly quickly. tions in Tokyo. In some cases, governmental Itabashi-ku began growing one on the south buildings have a green wall partly as a means of building of the ward office at the end of April making the public aware of the possibilities e.g. 2007, and its height of 10 cm had reached 10 me- Taito ward office. The walls are appropriate for tres by July 10th, approaching the top of the four- educational institutions where they can also claim storey building. On the hottest days, the tempera- an educational role for students e.g. Iwakura Sen- ture difference between indoors and outdoors ior High School (Taito-ku, near Ueno station), was of the order of 10 oC. (Itabashi ward office Seijō Gakuen High School (Shinjuku-ku), and Rik- 2007) kyō University (Ikebukuro). Green walls can also The curtains can be removed after summer, be used for large buildings such as theatres (e.g. thereby allowing the classrooms and other rooms Senshu Kogekijō, also known as Sakura Gekijō, in to benefit from the warm sunshine during the ). They have also been constructed on the colder months of the year. outer sides of large ventilation shafts providing Green curtains can also be used for tall apart- air for the underground areas to the west of Shin- ment buildings. A traditional way of keeping juku station. Green walls thus can be constructed houses cool during summer in Japan is to place in a range of situations. bamboo screens (‘tsudare’) over windows. How- ever, if a green curtain is placed so that it slants Green curtains outwards, it allows the passage of air along the A green curtain is somewhat similar to a green balcony, increasing the effectiveness of cooling. In wall. It is grown vertically along nets, either up- Nerima-ku, the cooling effect of a green curtain wards or downwards, with a gap between the was found to be sufficient for air-conditioning to HARRISON :TheUseofGreenery to Combat Urban Warming in Tokyo 63 be unnecessary. (NHK 2005) The curtain can cut worth considering whether tax laws could be out up to 80% of the incident sunlight, as well as amended to provide incentives for returning such cooling via transpiration, reducing indoor tem- land to its natural state, thereby increasing the peratures by 5 oCeven on days when the tem- total area of green space. perature exceeds 30 oC. The government set rather strict goals to achieve regarding the number of tropical nights Conclusion in Tokyo; however, their efforts so far have Temperatures in Tokyo have increased dra- yielded positive results, with the 5-year averages matically over the past decades due to the heat for tropical nights showing a decrease until 2009, island effect, to the point where the heat is di- but since then there has been a sizeable increase rectly affecting the quality of residents’ lives and and more can be done. There certainly seems to affecting their health. Tokyo has taken the lead in be determination to achieve the goals, and it is adopting measures to mitigate this urban warm- hopeful that the worst effects of urban warming ing, most notably in the issuance of an ordinance may be alleviated in the coming years, even requiring the construction of green roofs on though the government seems set to fail to meet many of the larger buildings. Although at present its targets. the regulations only require green roofs on new and renovated buildings, with the successful im- References pact of the regulations becoming evident, it is Asahi Shinbun. (2006). Minori aru okujō ryokka worth considering whether such an ordinance (Green roof bears fruit). Asahi Shinbun Octo- should be expanded to cover all large existing ber 31, 2006, p. 39. buildings. Aichi University of Education. (2007). Toshi Other greening measures have also demon- ryokka to okujō to hekimen ryokka (Urban strated their effectiveness. Green walls are be- greenification and the construction of green coming more popular and mimic the beneficial roofs and green walls). http : //www.biolo. effects of green roofs. Green curtains offer a sim- aichi-edu. ac. jp / SIchihashi/1Monday7. PDF ple and cheap means of not only helping to fight Accessed August 27, 2007. urban warming but also a way of making an im- Beatley, Timothy. (2000). Green urbanism: Learn- mediate and substantial impact on the comfort of ing from European cities. Washington DC: school classrooms that lack air-conditioning. Island Press. These steps, plus the plans for turfing school Earth Pledge. (2005). Green roofs: ecological de- playgrounds, are receiving strong encourage- sign and construction. Atglen, Pennsylvania: ment from the metropolitan government, which Schiffer Publishing. has clearly established itself as a leader in the Green Roof Centre, Sheffield. (Date unknown). Do field in Japan. something worthwhile - grow a roof. http : // Many parts of Tokyo have a patchwork of www.thegreenroofcentre.co.uk/pages/what. small farming plots. However, changes in the tax html Accessed August 27, 2007. laws in 1972 meant that the number of plots de- IGRA (International Green Roof Association). creased, with a significant number being used for (Date unknown). Benefits of green roofs. purposes such as asphalted car parks. It may be http : //igra-world.com/green-roof-benefits 64

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cessed August 27, 2007. (In Japanese) unknown). Ryokka keikaku to okujō ryokka- Moriyama Masakazu. (2004). Hiito airando no yoku aru shitsumon (Greenification plans and taisaku to gijutsu (Countermeasures and the greenification of roofs - frequently asked techniques for heat islands). Kyoto: Gakugei questions). http : //www 2.kankyo.metro.to- Shuppansha. (In Japanese) kyo.jp/green/keikakusyoseido/faq.htm Ac- Murayama Kouji. (2005). Necchūshō no kikendo ga cessed August 28, 2007. (In Japanese) takaku natte iru! (The danger of heat stroke TMG (Tokyo Metropolitan Government). (2007 a) is increasing). In : Mikami Takehiko (ed.). www. 2. kankyo. metro. tokyo. jp / green / Tōkyō ijō kishō (Tokyo’s unusual weather). shyukei / sidoujisseki 1803 made. pdf Ac- Tokyo : Yōsensha. 2005 : 12, 13. (In Japanese) cessed August 27, 2007. (In Japanese) NHK (Nippon Hōsō Kyōkai). (2005). Gaman deki- TMG (Tokyo Metropolitan Government). (2007 b). nai! Natsu no mōshō (Unbearable! The fierce Toshi to chikyū no ondanka taisaku-kōtei no summer heat). July 28, 2005. http : //www. shibafuka (Countermeasures against the nhk.or.jp/gokinjo/backnumber/050728.html warming of cities and the world - turfing Accessed July 29, 2005. (In Japanese) school grounds). Tōkyōto kankyō hakusho NHK (Nippon Hōsō Kyōkai). (2007). Mijika na kon- 2007 (Tokyo environmental report 2007). chū ni ihen ari. (Something strange is hap- 2007 : 31. (In Japanese) pening to our familiar insects). Close-up Gen- Tokyo Environment Bureau. (2007). Kōtei no shi- dai No. 2433, June 26th, 2007. (In Japanese) bafuka (Turfing schoolgrounds). www 2. Nikkei Ākitekuchua. (2003). Jitsurei ni manabu kankyo.metro.tokyo.jp/kouteisibahu/index. okujō ryokka (Green roofs: learning from ac- htm Accessed March 10, 2008. (In Japanese) tual examples). Tokyo: Nikkei BP Shuppan. Tokyo Environment Bureau. (Date unknown). (In Japanese) Tōkyōto no hiitoairando genshō ~ atsuku naru Ojima Toshio. (2002). Hiito airando (Heat islands). Tōkyō (Tokyo’s heat island phenomenon - Tokyo : Tōyō Keizai Shinpōsha. (In Japanese) Tokyo becomes hotter). http : //www 2. Sorenson, Andre. (2002). The making of urban kankyo.metro.tokyo.jp/heat/heat 1.htmAc- Japan. London: Routledge. cessed February 24, 2007. (In Japanese) Taito-ku ward office. (Date unknown) Okujō . (2007) Necchūshō ni ryokka oyobi hekimen ryokka nit suite (The goyōshin(Vigilance against heat stroke). http : greenification of roofs and walls). http : // //tfd.metro.tokyo.jp/lfe/kyuu-adv/heat_dish www. city. taito. tokyo. jp / index / 000023 / 19-a.htm#2 Accessed August 22, 2007. (In 017308.html Accessed September 18, 2007. Japanese) (In Japanese) Toshi Ryokka Gijutsu Kaihatsu Kikō. (2003). TMG (Tokyo Metropolitan Government). (2001). Okujō ryokka no Q&A (Questions and an- Okujōtō ryokka no suishin (The advancement swers about green roofs). Tokyo: Kajima of greenification of roofs etc.). http : //www. Shuppankai. (In Japanese) chijihon.metro.tokyo.jp/hyokahp/h 13/h 13 Toshi Ryokka Gijutsu Kaihatsu Kikō 2006 (2006). PDF/16.pdf Accessed August 27, 2007. (In http : / / www. greentech. or. jp / gijyutsu. Japanese) syoseido.html Accessed August 27, 2007. (In TMG (Tokyo Metropolitan Government). (Date Japanese) 66

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