Urban Ecological Research in Singapore and Its Relevance to The

Landscape and Urban Planning 125 (2014) 271–289

Contents lists available at ScienceDirect

Landscape and Urban Planning

j ournal homepage: www.elsevier.com/locate/landurbplan

Research Paper

Urban ecological research in Singapore and its relevance to the

advancement of urban ecology and sustainability

∗

Puay Yok Tan , Abdul Rahim bin Abdul Hamid

Department of Architecture, National University of Singapore, Singapore

h i g h l i g h t s

•

Urban ﬂora and fauna studies dominated past two decades of ecological research.

•

Studies on ecology in Singapore far exceeded studies on ecology of Singapore.

•

Mechanistic understanding of urban ecological patterns and processes is lacking.

•

Studies on ecology of Singapore are needed to improve local urban sustainability.

•

A framework and key strategies are proposed to encourage such studies in Singapore.

a r t i c l e i n f o a b s t r a c t

Article history: The drastic changes in the natural environment of Singapore from the beginning of recorded settlements

Available online 4 March 2014

to the present day present numerous opportunities for understanding how urbanization has affected the

ecology of the island city-state. On the one hand, the almost complete clearing of the original tropical

Keywords:

lowland forests and the ensuing catastrophic extinction of the original biodiversity, suggest how cities

Urban ecology

ought to avoid the same developmental pathway. On the other hand, the relatively high percentage of

Urban ecosystems

vegetation cover that the city has achieved due to effective urban greening policies suggest that oppor-

Singapore

tunities still exist to restore functions associated with a healthy urban ecosystem. This paper reviewed

Urban sustainability

Resilience urban ecological research on Singapore conducted between 1991 and 2012, and summarized the key

Livability ﬁndings according to the state factors of an urban ecosystem. The review showed that the large majority

of the studies were focused on biodiversity, and were on the ecology in a city. It revealed gaps in urban

ecological knowledge of Singapore, especially in relation to how studies on the ecology of the city need

to link urban ecological research to issues of urban sustainability. Three key strategies are suggested to

advance knowledge in this area. These are, to focus on long-term ecological studies in Singapore as an

example of a high-density equatorial urban ecosystem, to consciously treat the built component of the

urban environment as a key component of urban ecological studies, and to leverage the strong interests

in eco-city development as ﬁeld experimental sites for urban ecological studies.

1. Introduction dimensions of societies, which will require adaptive urban gov-

ernance and urban planning to bring about inclusive development

The growth of urban populations is projected to occur most and sustainable economic development (Yap, 2011). From an eco-

rapidly in Asia over the next four decades (Montgomery, 2008). logical perspective, drastic land use changes that accompany urban

From a socioeconomic perspective, this is likely to bring about population growth can lead to sustained ecological impacts in

marked changes in the demographic, cultural and political air and water quality, city and regional climate, and biodiver-

sity loss (Elmqvist, Alfsen, & Colding, 2008; Grimm et al., 2008),

often with impacts that extend beyond the immediate boundaries

of urbanized regions. Within urban areas, these adverse impacts

∗

Corresponding author at: Department of Architecture, National University of

often manifest in poor urban living conditions which may not be

Singapore, 4 Architecture Drive, Singapore 117566, Singapore. Tel.: +65 65163531;

reversed by further growth in per capita income (Ooi, 2007; Yap,

fax: +65 67793078.

2011). Urbanization is therefore a key driver of socio-economic and

E-mail addresses: [email protected] (P.Y. Tan),

[email protected] (A.R.b. Abdul Hamid). environmental changes that affect large regions of Asia, directly

http://dx.doi.org/10.1016/j.landurbplan.2014.01.019

272 P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289

and indirectly, and which leads to signiﬁcant concerns of the better understanding of how its internal processes affect its prop-

future sustainability of these areas. Yet, being large agglomerations erties can emerge. For instance, societal consumption of materials

with high concentrations of ﬁnancial resources, innovation, human and resources can be studied as aggregated ﬂows of energy and

resources, and efﬁcient resource use, urbanization should also not materials occurring in and out of an urban ecosystem, and this

be neglected as a possible solution in the quest for sustainability knowledge can in turn be applied to understand a city’s sustainabil-

(Rees & Wackernagel, 1999; Wu, 2010). Therefore, understanding ity (Kennedy, Pincetl, & Bunje, 2011) and livability (Newman, 1999).

the patterns of urbanization and its attendant impacts on the social, The role of changing patterns of urbanization on the delivery of

economic and environmental functions of cities is critical in the ecosystem functions through biophysical processes can also reveal

development of solutions for urban sustainability. the impact of different urban patterns on resource consumption

Within Southeast Asia, Singapore represents an extreme case of (Alberti, 2010), which is intimately linked to sustainability con-

urbanization, which is perhaps a condition of it being a city and cerns of urban regions. Taking such a systems approach also allows

a state. As a state, Singapore currently has the lowest amount of drivers of change and the impacts of such changes to be understood

its original forest area left intact compared to its Southeast Asian through a common currency of energy or material that reside as

neighbours (Zhao et al., 2006). Of the original lowland tropical rain- stock in the ecosystem, or which ﬂows in and out of the ecosys-

forest that almost entirely covered the island before the founding tem using urban metabolic analyses. Foundational knowledge in

of modern Singapore in 1819, only 200 hectares (Corlett, 2011), or various aspects of landscape and urban ecology, such as in char-

0.28% of its current total land area of 714 km remains. This mas- acterizing patterns of urbanization, urban ecosystem services, and

sive transformation occurred within a century from its modern human ecology can then be integrated and explicitly linked towards

founding as a British trading post, initially driven by land clear- the fulﬁlment of urban sustainability objectives (Wu, 2010) (see

ing for the cultivation of cash crops (Corlett, 1992). In fact, when also Breuste & Qureshi (2011)).

H.N. Ridley, the ﬁrst director of the Singapore Botanic Gardens pub- As the most urbanized state in Southeast Asia, and an example of

lished the ﬁrst compilation of the ﬂora of Singapore in 1900, he a high-rise, high-density and compact city, Singapore can present

reported that “a great deal” of the original forest had been felled, a snapshot of what rapidly developing cities could be like in the

“ . . and every year still sees the disappearance of some woodland, future, and therefore lessons that are applicable to other fast grow-

so that in several of the localities . . . few traces of any native plants ing urban regions of the world. However, there is to-date no review

can now be found” (Ridley, 1900). Subsequent land clearing was undertaken on the range of urban ecological research conducted in

driven by urbanization in response to population growth and eco- Singapore, or a synthesis of how the research can be used to develop

nomic development. Land developments for commercial, industrial a picture of Singapore as an urban ecosystem. This paper aims to

and infrastructure needs were greatly intensiﬁed during the period address these gaps. The objectives of the paper are to: (1) summa-

of rapid industrialization between the 1960s and 1980s (Neville, rize the past two decades of urban ecological research in Singapore,

1993). By 1965, Singapore’s population was already considered to (2) describe how urban ecological research can be better linked to

be 100% urbanized (McGee & Greenberg, 1992). This was in con- promote urban sustainability, and (3) identify strategies for further

trast to urban populations ranging from 13% to 36% in Malaysia, research to enable such functional relationships to be forged.

Thailand, Indonesia and the Philippines at the same period. As a city,

its urbanization proﬁle is also comparatively rapid and extensive.

The percentage of built-up area (broadly equivalent to the deﬁni- 2. Two decades of urban ecological research in Singapore

tion of “urban area”), was about 49% in 1999, which had almost

doubled from 27.9% in 1960 (derived from Wong & Yap, 2004). Using the approach of Pickett et al. (2011) as well the human

The rate of urbanization is high even when compared to the expo- ecosystem framework described therein, we examine the past

nential increase in urban areas of Phoenix and Las Vegas, two of two decades of urban ecological research in Singapore, catego-

the fastest growing metropolitan regions in the United States (Wu, rized according to the state factors of the ecosystem. As described

Jenerette, Buyantuyev, & Redman, 2011). The growth in urban areas in Amundson & Jenny (1997), ecosystems are “human constructs

in Singapore does not seem abated. Although the built-up areas was that break the continuum [of the earth’s surface] into manage-

projected to reach 60% by 2030 (Neville, 1993), it was seemingly able and differing segments for study”. Different ecosystems can

attained by 2012, accompanied by signiﬁcant changes in its land be distinguished by different assemblages of state factors, which

cover (Tan, Wang, & Sia, 2013). Given that urbanization continues in all ecosystems include the factors of climate, organisms, topog-

to be the most signiﬁcant cause of land use change in Singapore, raphy, parent material, time and humans, as well as other locally

it is critical to understand how its impacts could be better man- important factors such as ﬁre, coastal conditions, etc. (Amundson

aged, particularly in relation to the two fundamentally important & Jenny, 1997). We selected papers published between 1991 and

pursuits of urban sustainability and livability. 2012 (please see Table A.1 of the Appendix for more information

How can the impacts of urbanization in Singapore be stud- on the selection of papers), and examined urban ecological research

ied? Following the signiﬁcant progress made in the past two to in Singapore according to the following state factors: (1) urban cli-

three decades on how a city is also a novel or hybrid ecosystem mate, which refers to air and surfaces temperatures, atmospheric

(Alberti, 2009; Grimm, Grove, Pickett, & Redman, 2000; Pickett compositions, wind and solar radiation; (2) urban ﬂora, which com-

et al., 2011, 2001), we suggest the approach of understanding the prises both managed and spontaneous vegetation; (3) urban fauna,

impacts of urbanization by focusing on Singapore as an urban which comprises taxa of the animal kingdom; (4) urban soils, which

ecosystem. In this ecosystem, which is in essence, a tightly coupled is a simpliﬁcation of the state factor of parent material, and will

socio-ecological system, the biophysical and socioeconomic com- primarily be on disturbed urban soils; (4) urban biogeochemistry,

ponents interact with each other, driving changes and responding which is focused on the ﬂux and budgets of water, energy, nutri-

to disturbances. Urban ecological studies, or urban ecology as an ents, carbon, and pollutants, and (5) urban social factors, which

emerging integrative discipline (Pickett et al., 2008) provide the refer to humans as the dominant organisms of the urban ecosys-

scientiﬁc underpinnings to understand the patterns, processes and tem, and the social, economic and cultural institutions created by

functions within cities or any urban area, as well as the regional them. The review is limited to the terrestrial ecosystem, includ-

and global effects of cities (Grimm et al., 2008). Treating a city as ing the inter-tidal ecosystem of mangroves, and excludes studies

an urban ecosystem allows a highly complex system to be stud- on the coastal and marine ecosystem of Singapore. As an island

ied through conceptual frameworks and models, from which a nation, its marine ecosystems should be considered as an integral

P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 273

Table 1

to various levels of intervention to improve the conditions of the

Relative distribution of urban ecological studies based on the focus of studies (pat-

urban climate. The key observations from urban climatic studies in

tern, process, mechanistic), adapted from (McDonnell & Hahs, 2009). Studies of

Singapore are:

pattern refer to the characterization of the composition, spatial distribution and

structure of urban elements such as biodiversity, human behaviour, types of land

cover, etc.; studies of process refer to the characterization of interactions between (1) The urban climate of Singapore is affected by both urbanization

similar or different urban elements leading to changes in ﬂows and transformation

and urban activities. As with many other cities, Singapore expe-

of energy, materials and information; mechanistic studies investigate mechanisms

riences an urban heat island (UHI) effect. This is between 4 and

that lead to species and ecosystem responses to urbanization, and manifestation of ◦

7 C (Chow & Roth, 2006; Wong & Chen, 2005), which is moder-

patterns and processes. The number of + indicates the relative number of studies in

each focal area. ate compared to temperate cities of equivalent population sizes

(Roth, 2007). The UHI effect is temporally and spatially het-

State factors Focus of studies

erogeneous, and shows a “rural–urban gradient” (McDonnell,

Pattern Process Mechanistic

Pickett, & Pouyat, 1993), with the mean urban heat island inten-

Urban climate ++ + sity decreasing from commercial, to business, to residential, and

Urban fauna and fauna ++++ ++

to rural sites (Chow & Roth, 2006; Jusuf, Wong, Hagen, Anggoro,

Urban soils +

& Hong, 2007). In addition to land cover, heat released from

Urban biogeochemistry +

anthropogenic activities has a large inﬂuence on the urban tem-

Urban social factors +

peratures, an effect seldom reported in UHI studies (Quah &

Roth, 2012).

component of overall ecology of the island. The marine ecosystems (2) The urban climate is inﬂuenced by novel ecosystems created

are affected by terrestrial processes, such as storm water discharge, by land cover changes, which is illustrated by spontaneous

land reclamation, etc., and commercial activities such as ship move- bush ﬁres that periodically occur in grasslands. Grasslands is

ments in the coastal waters, and have possible reciprocal effects a novel ecosystem in Singapore not thought to exist prior to

on the terrestrial ecology. A search in SCOPUS database retrieved human settlement (NParks, 2010). Due to their susceptibility

more than ﬁfty relevant papers published between 1990 and 2012, to spontaneous bush ﬁres and proximity to human popu-

covering biodiversity assessment, reef restoration, pollutant accu- lations, bush ﬁres in turn create temporal increases in the

mulation, atmospheric deposition, biofouling, remote sensing of concentration of atmospheric particulate matter with possible

water properties, etc. The wide-ranging topics and number of stud- adverse health implications (Karthikeyan, Balasubramanian, &

ies concerned warrant a separate and substantive review; these are Iouri, 2006). This illustrates the reciprocal interactions between

therefore excluded from this paper. human action and ecosystem dynamics suggested in the human

The ﬁndings of the studies are categorized into sub-themes and ecosystem framework, for instance in Grimm et al. (2000).

summarized in Table A.1 of the Appendix. In the following sections, (3) The inﬂuence of regional land use changes on Singapore’s cli-

we describe the key observations from the studies, if any explicit mate shows that “no ecosystem is an island”, and regional

linkages can be drawn between the state factors and urbanization ecosystem processes do not respect national boundaries.

of Singapore, and where applicable, how the understanding devel- Biomass burning of neighbouring South-east Asian forests

oped from urban ecological studies have been used to formulate caused noticeable depositions of a wide range of organic and

policies. inorganic compounds into Singapore’s ecosystems (He et al.,

2011; He, Zielinska, & Balasubramanian, 2010; Yang, Nguyen,

2.1. Categories of urban ecological studies Jia, Reid, & Yu, 2012). This is over and above the tendency

for cities to have higher levels of acid and nitrogen deposition

One hundred and thirty seven papers were reviewed. We believe (Gregg, Jones, & Dawson, 2003). Such depositions are expected

the papers to be a comprehensive coverage of urban ecological to affect terrestrial and aquatic ecosystems of Singapore, but

research in Singapore over this period, but they are not exhaus- systematic assessment of long-term impacts remains to be

tive as grey literature has been omitted. Several publications that conducted. Although not conducted in Singapore, lower pho-

border between coastal and marine ecosystems were also omitted. tosynthesis of forest trees in Sarawak due to reduced level of

The large majority of the papers were on urban ﬂora and fauna photosynthetically active radiation (Davies & Unam, 1999) dur-

(65.0%), followed by urban climate (13.9%), urban social factors ing a widespread haze episode in 1997 showed the possible

(12.4%), urban biogeochemistry (6.6%), and urban soils (2.2%). The effects of prolonged haze periods on large areas of natural and

second decade in the period 1991–2012 on average had about 50% urban forests in South-east Asia. Transboundary ﬂows of air-

more publications per year compared to the ﬁrst decade, especially borne materials thus appear to be an important determinant of

for studies on urban climate and urban social factors, suggesting a the overall atmospheric composition, and the biogeochemical

growing research interest in these areas. budget of Singapore. In addition to possible ecosystem distur-

bances, such external ﬂows also have a socio-economic cost.

2.2. Urban climate This was estimated to be USD $286 million during the 1997

haze, estimated from increased health care costs and reduced

The urban climate is determined by a set of interacting fac- tourism receipts (Quah (2002) and references cited therein).

tors such as local climatic patterns, geographical characteristics (4) Urban climatic studies point to a range of possible interven-

that determine whether continental or maritime climate prevail, tions, such as green spaces (Wong & Chen, 2005), street trees

urban surfaces (vegetation and water cover versus built surfaces), (Wong & Jusuf, 2010), rooftop greenery (Wong, Chen, Ong, &

and anthropogenic activities. The ﬁrst two factors are not imme- Sia, 2003), urban morphology (height to width ratio of street

diately within human’s control, although anthropogenic activities canyons) (Goh & Chang, 1999) and types of building mate-

that has accelerated since the Industrial Revolution are a direct rials (Priyadarsini & Wong, 2005) to mitigate the UHI effect.

cause of global climate changes that will inﬂuence the prevail- The empirical relationships established in these studies, though

ing local climate. The latter two factors arise directly from human largely focused on investigations from a single-discipline

actions shown in the pace and extent of urbanization, as well as perspective, have provided the basis to launch interdisci-

the urban morphology of cities through the practice of urban plan- plinary investigations that are more predictive than descriptive,

ning and design. By the same corollary, these are more amenable and which can eventually be used to understand the urban

274 P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289

climatic impacts of different urban plans and designs (Wong, Zn, Cr and Mn 2–5 times higher in industrial areas compared to

Jusuf, & Tan, 2011). In fact, built upon the foundations of ear- the nature reserves (Zhou, Wong, Koh, & Wee, 1997), similar in

lier research, exploratory work has begun to use urban climatic range to observations cited in Pickett et al. (2011).

mapping methodologies in the planning of new townships and (2) The hydrological properties of soil are altered under urban con-

developmental regions in Singapore by scientists and national ditions, with soils in turfed areas of green spaces having water

planning and development agencies. inﬁltration rate and saturated hydraulic conductivity up to 200

times lower compared to soils in natural conditions (Rahman,

2.3. Urban biodiversity – ﬂora and fauna 1993), presumably due to compaction of urban soils arising

from human trafﬁc.

Urban ﬂora and fauna is an active area of research in Singapore.

The key observations from biodiversity studies in Singapore are:

Recent innovations in the use of specially formulated urban soils

will further add complexity and spatial heterogeneity to urban

(1) Singapore has introduced a high level of managed vegetation

green areas. For instance, structural soil which is used to over-

that has replaced native vegetation lost in the process of urban-

come compaction of horticulture soils (Rahardjo, Indrawan, Leong,

ization. Yee, Corlett, Liew, and Tan (2011) assessed the overall

& Yong, 2008), and growing media designed with ﬁltration proper-

vegetation cover to be at 57% in 2007.

ties in bioretention systems (Ong, Kalyanaraman, Wong, & Wong,

(2) The main drivers of species extinction were fragmentation of

2012) are being introduced into urban landscapes in Singapore.

native vegetation and further disturbances of remnant habitats.

These newer forms of urban soils alter the inﬁltration, retention and

The loss of native vegetation has led to signiﬁcant extinctions of

evapotranspiration of soil water, the urban climate (Bartens, Day,

native flora and fauna. The extinction in butterflies, fish, birds

Harris, Wynn, & Dove, 2009; Coutts, Tapper, Beringer, Loughnan,

and mammals was estimated to be 34–87% between 1819 and

& Demuzere, 2013), and can enhance urban biodiversity (Kazemi,

2003 (Brook, Sodhi, & Ng, 2003), and ﬂora extinction was about

Beecham, & Gibbs, 2011). The urban soil fauna is also a largely unex-

26% (Turner et al., 1994). This is comparatively high among 11

plored area of work. Based on preliminary studies, urban soils in

cities studied (Duncan et al., 2011).

Singapore are expected to harbour a high level of biodiversity, but

(3) Studies on species abundance and diversity in different habitats

this is likely to be dominated by exotic species (R. Corlett, personal

suggest two complementary approaches towards biodiversity

communication, July 31, 2012).

conservation in Singapore. The ﬁrst approach is the protection

of signiﬁcant patches of existing native vegetation, which still

harbour a high percentage of native ﬂora and fauna and which

2.5. Urban social factors

have a large impact on species diversity (Brook et al., 2003;

Castelletta, Thiollay, & Sodhi, 2005). This is corroborated by the

The understanding of human and social factors is arguably the

assessment of the importance of the management and use of

least investigated aspect of urban ecological studies in Singapore,

native vegetation towards slowing down the demise of extant

but is of central importance in the human ecosystem framework

species in a study of extinction debt carried by cities (Hahs

(Grimm et al., 2000; Pickett et al., 2011). In this framework, the

et al., 2009). The second approach builds on studies by Lian

preferences and decisions of individuals, households and commu-

and Sodhi (2004) and Sodhi, Briffett, Kong, and Yuen (1999)

nities drive changes in the rate of urbanization, rate of material

that highlighted the conservation value of managed vegeta-

consumption, removal of native vegetation, introduction of exotic

tion in urban sites in the presence of suitable plants and larger

species, etc., leading to secondary effects such as altered processes

native vegetation fragments. These studies point to the role of

of heat and material exchanges and composition of biodiversity.

increasing habitat connectivity or defragmentation in highly

The changes are eventually manifested in the status of the state fac-

built-up areas for conservation objectives, especially in view

tors in the urban ecosystem of Singapore, such as the urban climate,

of the highly fragmented landscapes in Singapore.

which in turn affects Singaporeans’ well-being in either a virtuous

(4) Studies on the distribution and diversity of extant species cor-

or a vicious cycle. We are not aware of any studies that have used

roborated those conducted in other cities. They support the

this conceptual framework explicitly to link human factors and the

general observation that urban areas can harbour a high level

biophysical environment of Singapore. Several perception studies

of biodiversity (see sections on “Biodiversity and population

showed that Singaporeans in general, accept the need to co-exist

studies” in Table A.1 of Appendix A), but with a large majority

with biodiversity (Sha et al., 2009), and favour more greenery to

comprising urban exploiters and exotic species. For instance,

be introduced into their immediate living spaces within buildings

exotics constitute about 85% of extant ﬂora of Singapore (Chong,

(Yuen & Hien, 2005). There is also a fairly active advocacy by the

Tan, & Corlett, 2011).

civil society for a more balanced approach towards development,

particularly with regards to giving due considerations to the con-

2.4. Urban soils

servation of the natural heritage (please refer to the section on “civil

society advocacy” in Table A.1 of Appendix).

There is a paucity of information on the heterogeneity and com-

Human-nature conﬂict is emerging as a concern. In urban

position of soils in Singapore, and how these might inﬂuence or

areas where humans and other biodiversity share spaces in close

underpin ecological processes and functions. With only 0.28% of

proximity, incidences of human-nature conﬂicts such as those

land that has not been directly disturbed by humans, soils in large

between humans and macaques (Sha et al., 2009; Yeo & Neo,

areas of Singapore would have been altered from their natural

2010) have been documented. Such incidences were also reported

properties. In landscape areas for instance, backﬁlled soil mixes

in the news media, such as in Chia (2012) and Feng (2011),

introduced from differing soil formations in Singapore, or even

which sometimes unnecessarily heighten misconception and anx-

neighbouring countries create highly altered and heterogeneous

iety towards human–animal relationships (Yeo & Neo, 2010). All

urban soils. The key observations from a limited number of soil

these illustrate a novel ecosystem at play in which altered natural

studies in Singapore are:

processes, such as habitat disturbances and predation, create new

and dynamic relationships between humans and biodiversity in a

(1) A pattern of urban–rural gradient was observed in the compo-

socio-ecological system.

sition of heavy metals in soils, with concentrations of Pb, Cu,

P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 275

2.6. Urban biogeochemistry concentration, etc., and that the urban environment can harbour

a high level of biodiversity. The studies also provided several

Urban biogeochemistry is concerned with the study of the new insights. For instance, while it is known that urban waste

“transport and transformation of matter and energy in [urban] discharge and appropriation of nature’s resources by cities lead

ecosystems” (Kaye, Groffman, Grimm, Baker, & Pouyat, 2006), and to regional changes in biogeochemical cycles and climate, the

focuses on the ﬂuxes and budgets of water, energy, nutrients, reciprocal effect has seldom been explicitly studied. An island city-

carbons and pollutants occurring at the atmospheric, surface or state like Singapore which is surrounded by large regional land

subterranean layers. The methods of urban metabolism, through masses, can be severely impacted by changes in the regional for-

the study of mass ﬂuxes, or ﬂuxes of energy and its equivalents, est cover brought about by cities’ expansion or economic activities.

have been used to characterize urban biogeochemical ﬂows com- These changes cause transboundary movement of atmospheric pol-

pared to rural areas (Kaye et al., 2006; Kennedy et al., 2011). The lutants that affect the health of humans and local ecosystems,

key observations from urban biogeochemical studies in Singapore and which can also bring about signiﬁcant economic costs. An

are summarized below: ecosystem assessment of Singapore is therefore incomplete unless

the inﬂuence and input of “external” materials are accounted

(1) Singapore’s urban metabolic rate, revealed by per capita domes- for.

tic consumption of materials, had increased concurrently with The implementation of highly urbanized water catchments in

economic growth (Schulz, 2007). Despite the signiﬁcant shift Singapore shows that the urbanized land cover, in contrast to veg-

from a production-based to service-based economy, there was etated water catchments, can also provide a valuable ecosystem

no improvement in the overall productivity of material usage. service as catchment areas for water harvesting. It demonstrates

The city is thus still expanding and appropriating resources such that when considering how the biophysical environment of the city

as fossil fuels, construction minerals, industrial minerals, etc., can be constructed to better mimic natural systems, for instance

from the natural environment. in its heat and water budgets, the built elements in the urban

(2) In addition to urbanization and domestic consumption, eco- ecosystems can become complementary rather than antagonistic

nomic activities i.e. external trade, was an important predictor elements in the pursuit of sustainability. In the case of Singapore,

of ﬂows of biomass, fossil fuels, construction minerals, indus- with its high-rise and high-density built environment, the total

trial minerals and other secondary products over a 41-year amount of built surfaces inclusive of all the vertically stacked ﬂoor

period. For instance, the level of imported greenhouse gases areas of building and their facades will exceed the area of veg-

(GHG) emissions was 4–5 times that of direct GHG emissions etated surfaces in the city by several folds. These built surfaces

originating from within Singapore (Schulz, 2010). should thus be also assessed for their use to improve the biophysical

(3) Studies on the feasibility of urban stormwater catchment and environment of the city, rather than the singular focus on vege-

the eventual realization of an urban reservoir (Marina Reser- tated surfaces in traditional ecological studies. These ﬁndings are

voir) in 2011 to meet Singapore’s water needs (Cheong, 1991; important in the consideration of research directions elaborated in

Lim, Leong, Tiew, & Seah, 2011) show that despite the lack subsequent sections.

of large vegetated water catchment areas in a highly built- Our review is useful for highlighting gaps in the knowledge of

up environment, an urban water catchment can be harnessed speciﬁc state factors and interactions between them, especially

for the provision of urban ecosystem services. Although pollu- in relation to urban functions. This can be illustrated by several

tant loading from urban runoff into receiving bodies have been examples. For instance, the relative importance of urbanization

reported (Chen, Tan, & Tay, 1995; Chua, Lo, Shuy, & Tan, 2009), it versus anthropogenic activities on the intensity of UHI remains to

appears that threshold levels of pollutant loading have not been be determined, but is an important question as the knowledge can

breached for important pollutant species, and that downstream inform planners of the type of interventions that are most effective

water treatment is able to cost-effectively treat the reported in mitigating UHI. In the area of urban soils, the reasons for the

pollutants. observed high biodiversity, the implications of soil biodiversity on

soil and vegetation productivity, as well as how these processes

The urban metabolic studies reinforce earlier observations on might be affected by human activities remain unknown. The

the influence of regional flows of atmospheric materials, in that numerous knowledge gaps in urban soil ecology identified by

economic transactions in the form of imports and exports need to Byrne (2007) apply equally to tropical soils, and highlight urban

be considered in material budgets to fully reﬂect an urban ecosys- soils as a key area requiring active research. Similar to the state

tem’s processes and the appropriation of services and resources factor of soils, the limited studies on urban social factors as a

from outside its political boundaries. The studies also point to a determinant of various urban phenomena also point to severe

recurrent theme on the human factor (and their associated social inadequacies in this facet of socio-ecological research. It is an area

and economic activities) as a key driver of ecosystem dynamics. deserving more urgent attention given the central importance of

human as the actor and link in determining urban patterns, func-

2.7. Gaps in urban ecological studies in Singapore tions and long-term sustainability (Boone, 2013). In addition to its

use for pinpointing such speciﬁc knowledge gaps, our research also

These studies form a collective documentation of the changes highlighted gaps in the types of research that will be useful going

in the components of the ecosystem of Singapore following sig- forward. There is a signiﬁcant shortfall in studies that have moved

niﬁcant and rapid transformation of land cover and pattern, beyond descriptive studies, to those that are explanatory, mecha-

accompanied by equally signiﬁcant socio-economic developments. nistic or predictive. Using the classiﬁcation of McDonnell and Hahs

The state factors of urban ﬂora and fauna are relatively well- (2009), we assessed the relative distributions of studies according

studied, which aligns with the general observation that studies to whether they are centered on pattern, process, or mechanistic

of habitats and organisms dominate early ecological research in studies (Table 1). Studies of patterns, such as the spatial distribu-

cities (Alberti, 2009; McDonnell, 2012). Information on the other tion of species, population studies, spatial and temporal proﬁles of

aspects of the state factors is however, far more limited. The urbanized areas, urban–rural gradients in soil characteristics and

studies nevertheless, reinforce several currently known patterns pollutant loads, etc., are the most commonly conducted studies.

in urban ecosystems, such as formation of urban heat island, Studies related to processes, such as correlative studies between

urban–rural gradients in ambient temperature, soil heavy metals urban temperature, urban geometry and land cover, species

276 P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289

richness and land cover, or between nutrient recycling and land development of policy and planning of sustainable cities is synony-

cover, etc. are comparatively scarce. We use “mechanistic” studies mous with the practice of urban ecology (cited in Evans (2011)).

to refer to studies that derive causal relationships to explain The different perspectives of urban sustainability are clearly

patterns. For instance, mechanistic studies seek to explain why a important in the context of situations to which the concept is

higher carbon sequestration potential might exist in urban com- applied. In linking the concept to urban ecosystems, we suggest that

pared to natural areas due to the use of improved horticultural soils urban sustainability can also be conceived as a measurable prop-

compared to native, nutrient-poor tropical soils, or due to better erty of the urban ecosystem. As a property, it is directly inﬂuenced

care in meeting water and nutrient needs. We suggest that a mech- by the changes in, and the interactions between state factors of the

anistic approach to urban ecological studies has yet to be effectively ecosystem triggered by socio-economic and biophysical drivers. It

used locally, but is important to derive generalizations that can be takes a snap-shot of the dynamic state of the urban ecosystem,

deployed through urban planning and design for more sustainable but importantly, allows targets to be set using a wide a range of

urban patterns and forms. Shochat, Warren, Faeth, McIntyre, and metrics and indices. While there is no stable end-state of sustain-

Hope (2006) for instance, illustrated the use of mechanistic urban ability in a city (Pickett et al., 2013) which can be measured by

ecology to identify the ecological and evolutionary mechanisms metrics and indices, targets are useful for initiating actions, direct-

that can explain the higher population density but lower species ing urban development towards a more sustainable direction, and

diversity often reported in urban areas. Possible reasons for fewer for monitoring progress. This is because the axiom “if you can’t mea-

studies using a mechanistic approach could be due to difﬁculties of sure it, you can’t manage it” is widely adopted and operationalized

higher resource needs and longer time for such studies (McDonnell as key performance indicators in public and private institutions.

& Hahs, 2009), or that it requires a combination of diverse expertise Numerous metrics and indices for measuring sustainability have

that can be difﬁcult to assemble within a single study. been developed, and these were recently reviewed by Gasparatos

There were only a few studies, such as Brook et al. (2003) and and Scolobig (2012). Categorized as “biophysical”, “monetary” and

Lim and Sodhi (2004) that attempted to explain observations of “indicator/indices”, the range of metrics and indices reﬂects the

biodiversity richness in relation to urban forms and population plurality in the interpretations of sustainability and value system of

density, or those of Schulz (2007, 2010) that take a city-scale view the user. Their use will necessarily vary according to the objectives

of its metabolic and material budget. Taken together, using the of sustainability assessment and the context of applications.

distinction between ecology in cities and ecology of cities (Grimm Similarly, important urban considerations of livability and

et al., 2000; McDonnell, 2012), the studies therefore reﬂect the resilience can be treated as characteristics of the urban ecosystem.

predominant focus in the study of ecology in Singapore, with As with the concept of sustainability, there is more than one per-

much less attention on the ecology of Singapore. While studies of spective of resilience, but all seem to convey the quality of a system

ecological patterns and processes in the city provide important in having the capacity of “preserving what we have and recovering

baseline information essential to understand and document to where we were” (quoted in Davoudi, 2012). In the context of

spatial and temporal changes in the city, it is difﬁcult to use the cities as socio-ecological systems, resilience is generally inter-

results to piece together a picture of the overall state of ecology of preted as “ecological resilience”, which recognizes the presence of

Singapore, largely as these studies have not been positioned within multiple rather than single, stable states that a city could assume.

an accepted model or theory of Singapore as an urban ecosystem. It refers to the ability of a city to tolerate disturbances without

It is therefore also difﬁcult to explicitly link the outcomes of changing “its basic structure and function or shifting into a quali-

the studies to an urban sustainability perspective of Singapore. tatively different state” (Wu & Wu, 2013). The centrality of human

Clearly, a conceptual framework, such as the conceptual scheme agency in a human-dominated ecosystem also confers the qualities

proposed in Grimm et al. (2000) is needed to draw out linkages of the capacity for adaption, learning and self-organization in a

that are already apparent, as well to form testable hypotheses resilient socio-ecological system (Folke, 2006). These are also

of how components of the urban system might interact with essential qualities for sustainability. Resilience is therefore linked

each other in processes that might not be immediately apparent to sustainability, and is viewed as a key approach or mechanism

now. We suggest below, how these challenges can also become towards sustainability (Evans, 2011; Pickett et al., 2013; Wu & Wu,

opportunities for developing research streams in the ecology of 2013). It is also suggested to be the “fourth dimension of sustain-

Singapore that can better answer questions of urban sustainability ability” (in addition to the other dimensions of economy, social

in response to further urbanization pressures. equity and environment) (Ahern, 2012). The degree of resilience,

in turn, is governed by the balance between socio-economic and

biophysical processes (Alberti & Marzluff, 2004), i.e. interactions

3. Linking urban ecological research and urban between state factors that determine relative levels of human

sustainability, resilience and livability or ecological functions to support human needs. More generally

using the economic concept of capital, resilience is determined

Urban sustainability is an abstract concept that has been by the level of natural, social, and built (and ﬁnancial) capital

described as a process that seeks a balance between the key assembled within the urban ecosystem (Pickett et al., 2013). We

dimensions of social sustainability, economic sustainability, natu- therefore suggest that resilience is a malleable property of urban

ral sustainability, physical sustainability and political sustainability ecosystems that supports, or prevents the progress towards a more

(Pacione, 2007). This is akin to consultative urban planning during sustainable state. Emerging frameworks, such as those developed

which multiple objectives are considered in developing a develop- by the Resilience Alliance (http://www.resalliance.org) are also

ment plan for the community concerned. It has also been described being explored for resilience assessment.

as a measure of the extent to which a city has achieved a desirable In addition to the twin agenda of sustainability and resilience,

state of sustainability at any given point in its developmental stage livability has emerged as a key pursuit of urban development

(Shen, Peng, Zhang, & Wu, 2012), as well as a pattern of urban devel- in cities (Holden & Scerri, 2013; Ooi & Yuen, 2010). This is also

opment closely linked to issues of urban governance (Ooi, 2009). shown in a range of livability indices that benchmark cities, such as

Urban sustainability is also fundamentally about growth and devel- the Global Liveability Report (http://www.eiu.com/) and Monocle’s

opment that improve the economy and quality of life but which Most Livable Cities Index (http://monocle.com), and organiza-

minimizes the use of environmental resources and impacts on the tions dedicated to the study of cities’ livability, such as Centre

environment (UNWCED, 1987). It has been suggested too that the for Liveable City (http://www.clc.gov.sg) and International Making

P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 277

Cities Livable (http://www.livablecities.org). Although it does not energy and carbon metabolism of the city. Using the conceptual

have a single, widely-accepted deﬁnition, livability can be broadly framework, one could also ask, given the low interest and afﬁnity

understood to be about meeting human needs, from existential to to nature among Singaporean youths reported in Kong, Yuen, Sodhi,

spiritual. Aspects of such needs are listed by Newman (1999) to and Briffett (1999), how does this social trait inﬂuence subsequent

include employment, health, leisure, accessibility, community, etc. behaviour and attitudes towards sustainability and resource con-

Livability is inﬂuenced by both the human and natural environ- servation for this generation of Singaporeans? Could this eventually

ment (Newman, 1999), and we suggest that it is also determined by lead to higher consumption patterns and waste generation, with

socio-economic forces. For instance, the current economic malaise consequential effects on the material ﬂow of Singapore measured

experience by several European nations has severely affected the through a sustainability assessment tool? Viewed using an urban

basic livelihood, health care provision and general well-being sustainability lens, the consequence of detachment from nature

of affected regions. Social institutions and their governance also among urban populations might then not be simply studied as an

determine the degree to which essential public services can be dis- inevitable social consequence of increasing afﬁnity among youths

tributed equitably across different social-economic classes, directly to videophilic activities, but one which has urban sustainability

affecting the livability of communities. Similar observations can be impacts and hence deserving some form of intervention.

made of the global ﬁnancial crisis of 2008 and 2009, which had Secondly, in linking studies of ecosystems patterns and pro-

been attributed to a system of low resilience (Wu & Wu, 2013). cesses explicitly with urban sustainability measures, the outcomes

This demonstrates the link between depressions in livability and of such studies will be better appreciated by policy makers and have

the resilience of urban regions. Livability is also linked to sus- higher likelihood of being utilized in urban planning and design.

tainability. For instance, livability is described as an expression of Urban planning is typically a prescriptive process guided by a set

human desires, and sustainability as the capacity to deliver those of planning parameters, such as those that are inherently mutu-

desires through time (de Chazal, 2010). Taking a broader view ally exclusive in nature (e.g. development density versus conserved

in the context of a socio-ecological system, livability draws on area, built-up area versus green space coverage, road density versus

economic, social and natural capital from the ecosystem to meet cycling network, etc.). It is often a zero-sum process driven by trade-

human needs, whereas sustainability is concerned about the capac- offs between competing land needs, and unless such tradeoffs can

ity of the system and intergenerational equity to meet such needs be understood using a common currency such as one of available

in the long-term. sustainability indicators, it is difﬁcult to fully understand the impli-

We propose a framework to illustrate the key ideas described cations of decisions at the system level. By devising urban ecological

above (Fig. 1), focusing on aspects of urban sustainability. The studies which measure the consequences of trade-offs, e.g. of com-

framework recognizes the external impacts of socio-economic peting land use allocation on urban sustainability, there is a closer

factors, such as the world and regional economy, geopolitics, link between the ends (application) and the means (research) in

human migration patterns, health epidemics, etc., which have large urban ecological studies. Implementing such studies requires an

impacts on a small, highly trade-dependent and open economy of interdisciplinary approach that involves multiple disciplines col-

Singapore. It also recognizes the vulnerability of Singapore as a laborating to answer systems level questions using this common

small island city-state to the inﬂuence of global climate changes, framework. We believe that when studies are framed to probe

sea level rise and transboundary movement of atmospheric pollu- changes in overall ecosystem properties, they are likely to yield

tants on local ecosystem functions. It recognizes that internal state more actionable outcomes that can be used by policy makers.

factors are not independent, but interact among each other. Natu- A transdisciplinary approach, which has been deﬁned as cross-

ral, built and socio-economic components are conceived to be the disciplinary interactions between different scientiﬁc disciplines,

primary clusters of state factors within the ecosystem. The natu- and “non-academic stakeholders and government agencies guided

ral factors comprise the key factors traditionally associated with by a common goal” (Wu, 2006), can also engender better research-

a natural ecosystem but which has become highly altered in an to-policy translation. The early joint studies in urban climatic

urban ecosystem. The built environment factors, such as buildings, research involving urban climate modellers, building scientists,

infrastructure and tele-communications, represent the city’s stock plant scientists and active participation of policy makers in the

of energy and materials appropriated from nature during urbaniza- assessment of the urban green spaces as a mitigating factor for

tion. Because the built component is typically large compared to the urban heat island mitigation bears resemblance to such a transdis-

natural factors, it is shown as a separate cluster in the framework. ciplinary approach. The results of these studies had been translated

Socio-economic factors comprise human’s social, cultural and eco- into recent government guidelines and targets for implementation,

nomic systems. The interplay between the state factors affects the such as the national-level mandatory green building rating scheme

stock and ﬂow of ecosystem services of the ecosystem, in turn (BCA, 2010), climate change mitigation strategies (NCCS, 2012),

affecting its properties, such as sustainability, resilience, and liv- and national sustainable development blueprint (IMCSD, 2009).

ability. These are not independent, but inter-linked properties of The involvement of multiple actors has fostered the formulation of

the urban ecosystem. evidence-based public policies, which would have been unlikely to

What is the usefulness of such a framework? Firstly, framing be achieved through single-disciplinary academic research alone.

urban ecological system in this manner allows more explicit asso- This perhaps illustrates the promise of transdisciplinary action as

ciations of cause and effect to be postulated, both horizontally an approach to deal with sustainability challenges described by

among state factors and vertically with overall ecosystem prop- Wu (2008).

erties, and which can then be tested as research hypotheses. For

instance, the vegetation cover of Singapore is expected to decline

4. Strategies for advancing urban ecological research

due to population growth and increased land developments over

the past ﬁve years. But what will this mean to the urban sustain-

We provide some perspectives on key strategies to shape

ability of Singapore? Rather than taking a single dimensional view

urban ecological research in the context of urban sustainability in

of just describing patterns of longitudinal changes, it will be more

Singapore. The suggestions are not exhaustive or exclusive, but we

meaningful if the changes could be correlated to impacts on the

believe that they will help to stimulate further use of a common

urban microclimate and energy consumption. The knowledge can

ecosystem approach to deal with the issues of urban sustainability

then be used to form predictive relationships of how vegetation

among scientists, urban planners, policy makers, and the commu-

cover changes in a city in turn lead to deﬁnitive changes in the nity.

278 P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289

Fig. 1. Conceptual framework linking the state of an urban ecosystem (bounded by dotted lines) to internal state factors that interact among themselves and which collectively

determine patterns and processes within the ecosystem. State factors are grouped according to the natural environment factors, built environment and socio-economic factors.

There are multiple pathways of interactions between broad group of state factors, as well as within each sub-group of factors (such as between urban climate and urban

biodiversity) (thinner black arrows). External drivers (thicker black arrows), such as global climate changes, transboundary pollution, world’s economy, etc., inﬂuence the

ecosystem. Patterns, processes and functions within a deﬁned urban ecosystem in turn determine the stock and ﬂow of ecosystem services and confer measurable properties

on the urban system (open arrows), such as sustainability, livability, and resilience. Urban sustainability can be assessed by a suite of sustainability assessment tools (from

Gasparatos and Scolobig (2012)).

4.1. Conduct an integrated research programme in urban ecology that is centered around an accepted model of urban ecosystem,

with a long-term horizon in Singapore as an example of a from which research projects can be initiated on various com-

high-density equatorial urban ecosystem ponents of the models, is likely to be more effective in allowing

synthesis of knowledge and generalizations to be drawn about

The types of questions that scientists ask and provide answers to the ecosystem. This seems an obvious strategy given the vari-

is founded on the concepts, models and theories that science collec- ous weakness and gaps highlighted, but the fact that there are

tively develop (Amundson & Jenny, 1997). A research programme few integrated research conducted locally suggests barriers and

P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 279

difﬁculties in orchestrating an integrated research programme. instead of the current practice of designing for immediate discharge

The Long Term Ecological Research centered around Phoenix and of stormwater runoff into a drainage infrastructure that takes up

Baltimore (Grimm et al., 2000) and lessons learnt from these pro- considerable land in any city, a commercial development could

grammes provide a useful operating model on how other similar be required to retain a comparable, if not higher amount of the

programmes can be initiated. They have also provided valuable sci- stormwater previously detained by a forested site which it has

entiﬁc foundations to enable a broad-based look at issues of urban replaced. Similarly, as trees reduce sensible heat and increase latent

sustainability. But questions of generalizability of current knowl- heat through a combination of higher albedo, shading and evapo-

edge across a wide range of context deﬁned by geography, culture, rative cooling, one could also ask if buildings can be designed to

history and politics remain unanswered (Pickett et al., 2011). Does mimic these functions through material selection and architectural

Singapore have unique properties because of its equatorial climate, design. This will then compensate for the loss of such ameliorative

high population density, high level of built-up areas, peculiar socio- functions provided by trees.

political culture, trade-dependent open economy, relative short but This will force a shift from the current mindset of mitigat-

rapid urbanization history, etc.? Do emerging generalizations on ing the impacts of buildings on its environment, to one requiring

the properties of urban ecological systems then apply to Singapore? buildings or any built infrastructure to also provide compensatory

The complexities embedded in such questions can only be man- ecological functions. In recognizing that the built environment is

aged through inter- and transdisciplinary studies conducted over also a major component of the urban ecosystem, the vertical and

an adequately long time frame, as well as undertaking comparative underground spaces of the city will also necessarily become rele-

studies across cities (McDonnell & Hahs, 2009) with the objec- vant focal areas for how the ecological performance of a city can

tive of conﬁrming generalizations in urban ecosystems (McDonnell, be improved. For instance, investigations can be directed towards

2012). For Singapore, there also needs to be an increased focus how vertical spaces can be created as important habitats for bio-

on framing urban ecological questions with a stronger or more diversity in a city environment. A similar approach should also

inclusive emphasis on the socio-ecological interactions, given the be applied to biodiversity conservation in Singapore. Given that

relative lack of studies in this area. One could ask, for instance to protected biodiversity areas constitute only 3.5% of Singapore’s

what extent does Singapore’s green environment (Tan et al., 2013) land area, focusing on protected vegetated areas alone will have

shape nature conservation and sustainability attitudes among the limited overall impact and could be ineffective in the long-run

citizenry, especially in the middle class with its appetite for mate- because of adverse environmental changes in the matrix surround-

rial consumption. Will this heighten the awareness of sustainability ing nature reserves (Laurance et al., 2012). It also misses the vast

concerns and lead to changed behaviour that reduces material opportunities provided by urban areas for biodiversity enhance-

consumption? Or will material consumption continue to grow ment (Rosenzweig, 2003).

as shown by Schulz (2007), and Singapore be trapped as an air-

conditioned nation (Hitchins & Lee, 2008) with a high per capita 4.3. Incorporate urban ecological research in eco-city

carbon footprint? Studies in Singapore may also provide better development

transferability of lessons learnt to emerging and rapidly growing

urban areas in Asia, notably in China and South-east Asia with their There is currently signiﬁcant interest to build eco-cities in var-

rapidly growing middle classes that drive material consumption ious parts of the world, such as Hammarby, Masdar, Songdo, and

in these economies. Singapore also presents several advantages particularly in China. While a standardized deﬁnition of “eco-city”

for conducting city-scale studies. For instance, because its city remains to be accepted, the term is generally understood to be

and national boundaries coincide, international trade data cap- intermixed with terms such as sustainable urban development,

tures detailed inventories of material ﬂows that are available for green movement, green cities, etc. (Roseland, 1997). An eco-city

almost the past ﬁve decades (Abou-Abdo, Davis, Krones, Welling, has also been suggested to be “a city that provides an accept-

& Fernandez, 2011). These will be useful for correlating city-scale able standard of living for its human occupants without depleting

metabolic studies with various facets of socio-economic and bio- the ecosystems and biogeochemical cycles on which it depends

physical changes. Biodiversity changes have also been relatively (cited in Wong (2011)). The emergence of eco-city development

well documented (Corlett, 1992). Local and international collab- in China is also remarkable, with more than 100 Chinese munic-

orations will be useful towards initiating such an ambitious but ipal governments, and 390 cities or towns being developed to

needed long-term research programme in Singapore. become eco-cities (Wong, 2011; Wu, 2012), and understandably

with varying degrees of success in achieving ecologically sound

4.2. Increase the focus of research on the built component of the urban development. However, given the sizeable developmental

ecosystem scale and the wide range of social, economic and environmen-

tal objectives associated with each development, eco-cities of the

Our review on the ecological research in Singapore showed the past, present and future present remarkable opportunities to forge

dominance of ecological studies on the biotic (living) component a better appreciation of how urban ecosystem models and con-

of the ecosystem. In the context of a dense, highly built-up city cepts apply to the development of sustainable urban development

of Singapore, one must ask if the focus could be better balanced ideals in a real-world situation. Collaboration among urban ecolo-

towards also placing a stronger emphasis on how the abiotic (built) gists, urban planners and policy-makers could be at several entry

component can be designed and managed to improve the urban points: at the conceptual development stage, at the design stage

ecosystem towards sustainability objectives. This concern arises which includes development of performance indicators for sustain-

because the city is likely to have a much higher cumulative area of ability assessment, and at the post-completion stage through the

built-up surfaces than vegetated surfaces, and that further urban- assessment and reﬁnement of conceptual or design ideas. Recent

ization pressures will place a limitation on how much vegetated Sino-Singapore collaborations in urban development in China are

areas can be retained, or injected into the dense built-up environ- examples of platforms for bringing urban ecological research into

ment of Singapore (Tan et al., 2013). Taking such a view will lead to practice, and for new insights to be gained. Some examples include

an examination of the environmental performance of a particular the ﬂagship eco-city development, the Sino-Singapore Tianjin

land development, e.g. a commercial property with an ecologi- Ecocity (see Baeumler et al., 2009), Sino-Singapore Guangzhou

cal lens, and force a comparison of its ecological impacts with Knowledge City (http://www.ssgkc.com), and the China-Singapore

that of a natural environment, like a forested patch. For instance, Suzhou Industrial Park (http://www.sipac.gov.cn/english/). Using

280 P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289

these established platforms allows scientists, planners, policy- the mechanisms that explain observed patterns and processes. The

makers and developers to apply lessons learnt from experiences focus of future efforts should thus be on the understanding the

gained in Chinese cities to other parts of the world, including ecology of Singapore, as understanding properties at the ecosystem

Singapore. level forces a more explicit examination of ecosystem level changes

This is notwithstanding that there are signiﬁcant gaps in our in association with issues of urban sustainability, livability and

current understanding of urban ecology, but such an approach resilience. Much also remains to be understood about Singapore

also recognizes that urban planning and design in practice do as an urban ecosystem characterized by equatorial conditions,

not wait for full scientiﬁc knowledge to be assembled. So while rapid and dramatic urbanization, peculiar socio-political condi-

limited time and business circumstances often do not allow for tions, etc., and this present considerable opportunities in urban

comprehensive or full feasibility studies to be conducted prior to ecology research with a long term focus.

development as mentioned by Wu (2012), there is likely to be sig-

niﬁcant opportunities for structured collaborations between urban Acknowledgements

ecologists and urban planners to monitor various aspects of eco-

city developments. This is akin to undertaking ﬁeld experiments. We thank the Shanghai Key Laboratory for Urban Ecological Pro-

Our experience in Singapore also suggests that a close collabo- cesses and Eco-Restoration for the invitation to present a paper

ration between scientists, urban planners and policy makers at at the conference on “Frontiers in Urban Ecology and Planning:

the research phase helps to narrow the gap in the translation Linking East and West Scholars to Advance Ecological Knowledge,

of research results into applied policies and guidelines. A similar Planning and Management of Urban Ecosystems” held at the East

approach can be applied in cross-disciplinary collaborations in the China Normal University. This paper is based on an earlier version

development of eco-cities. presented at the conference. We also thank Amy Hahs and Mark

McDonnell of the Australian Research Centre for Urban Ecology, as

5. Conclusion well as two anonymous reviewers for their helpful comments on

earlier versions of the paper. All shortcomings in the paper are ours

Urban ecological research has documented the changes and pro- alone.

vided useful information on the state of the ecosystem in Singapore,

as well as reinforcing key ideas from urban ecological research else-

Appendix A.

where. Some research results have also been used in formulation of

national level plans on sustainable development. Signiﬁcant gaps

See Table A.1

however, exist in that there is insufﬁcient focus on understanding

P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 281 of or

not

(key

fauna, urban

factors

are

(5) soils

Studies and

region(s) of state

C C

assessment which at

R, R R R R, ﬂora the

); urban An

S R S, C R S, S, C C R S R S, Scale C S S Investigation: S,

but of (

nature).

invasive); (2)

urban or

each

to For

Bulletin

in ﬂora. highlighted.

width polar

the experiments source

radiation); the

consists the

to spaces and a

affect deemed are setting. instance

speciﬁc species

urban

the

environment, is

biodiversity, Gardens’

urban excluded.

the for are solar

economy ﬂora

species. open temperature populations successfully

level.

explain affects urban or height

The

for

than volume extinct under been Singapore’s

biodiversity

which

to controlled

an open if

effect

Singapore alien of ecology, keywords Singapore,

have

species

green control, temperatures. dimension

in urban

hydrocarbons,

also

surface of demonstrating e.g.

city, to other the

vegetation,

effect trafﬁc fungi campus

likely sources,

Six

air

and and to Singapore’s

buildings.

using

Singapore. pollution,

, social,

Increasing

species

have

localized are and of

responsible

spatial

invasive and in

cover, heat,

due fauna, island in

whole

signiﬁcant Factors

urbanized

tropical

metals parks be

of aromatic

plants.

the 2012) observed a

composition or

ﬂora

(2011) in

ecosystem Singapore,

published,

to native

estate.

the

temperature human,

bodies heat of

and

al. most surface the

nutrients,

at urban, the

recognition

with

are

heavy air been

build-up building

health.

over higher et

than

procedures

on transboundary on August

urban infeasible the

of patterns.

vegetation

by and water

urban

urban, polycyclic consumption

housing of parcel(s), and 15 heat early be

density

have

temperature.

proposed and

the has to

of which grasslands

from the greenery,

Chong exotic to human

establishment on

the

air in

and

ﬂux

parks, rainfall land of Singapore,

correlated

in greenery

immediate activities were energy

urban

extent

the

atmosphere, documented

species phosphorus those explained more

likely street focus affect

studies

on heat April

Singapore, distance the

biogeochemistry. for methods surfaces,

the

mainly concentration

bryophytes that relation

are site(s),

few and

words: 12

ambient

canyon human system rooftop

island,

turn, intensity turn in

heat, the mostly

should

adjacent of

concentrations in in paved

very

words: 2011

(key occur ameliorate

is and including

signiﬁcantly (monsoonal) the island’s compilation

There

single

Selective impact

heat

between affects street to

scenarios is

can

exclusion and and

area of

nitrogen

the the also landscapes. studies (key ﬂux

intensity. the

(between

sites, inﬂuence

the As of affected fauna

anthropogenic of on on beneﬁts

that

urban invasives

the of cover, clearing

1990s

that development species. scale

pteridophytes,

seasonal

heat

reproductive

street, of the urban of included.

housing

JSTOR island

a atmospheric strong factors

anthropogenic

the the phosphorus, urban in buildings

correlation

land

Based vegetation a ratio

worst-case

early

directly of

forest

matter disturbed ﬂuctuations

at and C

thermal the

changes on events

heat been

(

(4) morphology, be

climate,

for Singapore.

lichens, the

of and

has public in

and

the

depositions

control

effective social

observed. assessment

to space, ﬁndings the in

scale

and width

managed

also

cryptogenic

particularly metals

changes Direct

the

need and

urban

to island and in

urban

form the

from algae,

the

urban,

seasonal changes

anthropogenic Singapore. impact

focusing

primarily 210 or for of green urban

showed

have the compared particulate on ecosystems. nitrogen

invasive);

use

in high-rise species

materials

dominate deemed

heavy as disturbance

the quantify acids, and

of (6)

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species species

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fauna and

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extinction diversity population Biodiversity State Habitat Urban Fragmentation Fragmentation Forest Table

P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 283 of

C R, R

S C S R R, C S, C R R S S R C Scale Investigation: S, to

in its

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Studies Studies Key Assessment A The The A An Characterization The Demonstration Nutrient A There and the composition. urban resource urbanization economy (inclusive Singapore’s former, life. documented seem will of attributed development urbanized runoffs. area, landscaped (reservoirs) trade vulnerability impact areas, future exceeded Australian highly 2002. al.

Morton al.

et &

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et Ng

Tan (2010)

Brook

Cuong

(2003);

(2002); (2011)

(2002) al.

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et et et et &

Burslem Research Bayen Ahyong Abou-Abdo Schulz Schulz Chen Cheong Chua Rahman Zhou (2003a); (2010); (2006) (2005); Joshi Chen Wong

)

and

metals characteristics

limitation species

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species (

biogeochemistry soils metabolism hydrology

factor

water heavy A.1

growth pollutants Urban Nutrient State Coastal Urban Soil Soil Urban Invasive Urban Table

284 P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 of

R, R

C C S C C S, Scale C Investigation: S, as

and

land urban the the

animal

model

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to be

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recreational nature of

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perception perception

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(2009b); Ng

(1995); Sovacool

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nature

)

needs conﬂicts Sha

urban laws factors

versus advocacy

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social

factor Research

society

A.1

conservation Urban State Human-nature Conservation Civil Perception Recreational Table

P.Y. Tan, A.R.b. Abdul Hamid / Landscape and Urban Planning 125 (2014) 271–289 285

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Tan Puay Yok, PhD is an Associate Professor in the Department of Architecture in the

system. Energy Policy, 38, 4848–4855.

School of Design and Environment of the National University of Singapore (NUS),

Sha, J. C. M., Gumert, M. D., Lee, B. P. Y. H., Jones-Engel, L., Chan, S., & Fuentes, A.

where he contributes to the Masters programme in landscape architecture, envi-

(2009). Macaque–human interactions and the societal perceptions of macaques

ronmental management and integrated sustainable design as well as other design

in Singapore. American Journal of Primatology, 71, 825–839.

studios. His research interests are in the areas of policies, systems and practices of

Shen, L., Peng, Y., Zhang, X., & Wu, Y. (2012). An alternative model for evaluating

greening and ecology of the built environment. Prior to joining the academia, he

sustainable urbanization. Cities, 29, 32–39.

served in Singapore’s national agency on greenery and conservation matter, and

Shochat, E., Warren, P. S., Faeth, S. H., McIntyre, N. E., & Hope, D. (2006). From pat-

was involved in the development of policies, operational work and management of

terns to emerging processes in mechanistic urban ecology. Trends in Ecology and

research programmes.

Evolution, 21, 186–191.

Sodhi, N. S., Briffett, C., Kong, L., & Yuen, B. (1999). Bird use of linear areas of a tropical

Abdul Rahim bin Abdul Hamid is a PhD candidate in the Department of Architecture

city: Implications for park connector design and management. Landscape and

in the School of Design and Environment of the National University of Singapore.

Urban Planning, 45, 123–130.

Prior to his graduate studies, he taught landscape architecture in School of Architec-

Tan, P. Y., Wang, J., & Sia, A. (2013). Perspectives on ﬁve decades of the urban greening

ture and the Built Environment, Singapore Polytechnic. He also has prior experience

of Singapore. Cities, 32, 24–32.

as a practicing landscape architect in Australia and Singapore. His dissertation is

Turner, I. M., Tan, H. T. W., Wee, Y. C., Ibrahim, A. B., Chew, P. T., & Corlett, R. T. (1994).

centered on the development of ecological network for enhancing biodiversity in

A study of plant species extinction in Singapore: Lessons for the conservation of

Singapore.

tropical biodiversity. Conservation Biology, 8, 705–712.