Bridges for animals

For a small country, Singapore has made tremendous efforts to safeguard the environment in the face of rapid urban development and climate change. Recently, local planning authorities have begun to pay more attention to the preservation and improvement of ecological networks in the city state.
In this article, we are privileged to have Mr Abdul Rahim bin Abdul Hamid, a researcher from the National University of Singapore, to provide us with insight into the issue of ecological networks in the urban environment.

Ecosystem, ecological networks and ecological links

An ecosystemis a community of living organisms (plants, animals, etc) in conjunction with the non-living components of their environment (air, water, soil, etc), interacting as a system.



When similar ecosystems  are in close proximity  or they are separated by a different ecosystem but connected by a corridor of suitable vegetation that facilitates the dispersal of certain animal species, they can form ecological networks and promote further interaction.

Urban avoiders, adaptors and exploiters

Ecological networks become important, especially in dense urban environments, because natural areas are always in danger of being isolated or totally removed as a result of urban development. Isolated land masses are highly susceptible to resource depletion, ultimately resulting in extinction of flora and fauna.

Species that prefer natural areas (urban avoiders or urban adaptors) have not evolved as fast as the rapid pace of developments. Thus, they prefer to remain within the natural areas or their edges. The species that prefer urban areas (urban exploiters) are usually different to those found in natural areas. Therefore, appropriate corridors for the dispersal of species are necessary to link between natural areas if they are far apart or isolated.

Consider the following scenario,
  • Butterfly A feeds on Plant A in Park A
  • Plant A starts to die out in Park A
  • Park A is close to Park B
  • Park B has Plant A
  • Butterfly A will die out unless it can find its way to Park B


For this to work, we have to understand the ecosystems inherent to Parks A and B. This will help identify the existing network and enable planners to intervene accordingly, such as setting up an appropriate link to connect Park A to Park B.
There are many types of eco-links. Some examples include:
  • Eco-bridges (Figures 5 – 7)
  • Eco-ducts
  • Intensive planting that mimics the habitats of certain species
  • Riparian corridors which are river corridors that mimics the habitat of certain species
  • “Stepping-stone” habitats which are pockets of similar vegetation type found along a line connecting the two ecosystems

Eco-Link @ BKE


Eco-Link @ BKE is an eco-bridge in Singapore.
The function of this bridge can be rationalised as follows (Figure 1):
  • Central Catchment Nature Reserve is a large, thriving ecosystem
  • Bukit Timah Expressway (BKE) cuts the Central Catchment Nature Reserve into 2 zones
  • The smaller zone, Bukit Timah Nature Reserve, is isolated and has significantly lesser flora and fauna compared to the Central Catchment Nature Reserve (larger zone)
  • This means less food and shelter for birds and bees in the smaller zone
  • A bridge was constructed for the purpose of providing access for animals in the smaller zone to the larger zone



Eco-bridges are different from conventional bridges, simply because animals don’t cross bridges the way people do. Some animals are really shy and require foliage cover when in transit. For example, the Colugo (Figure 3) will not cross the bridge unless conditions are forest-esque. The Common Myna (Figure 4), on the other hand, will fly over 4-lane highways without much fuss. This is why the eco-link is 50 m wide and is designed for extensive foliage cover. The curvilinear plan serves to channel animals towards the bridge (Figure 2).

Opportunities for eco–linkages in Singapore

There are many areas in Singapore where more robust ecological networks can be established. For instance, the two distinctive ecosystems in Tengah and Jurong Lake (Figure 9) have the potential to be connected via the channel in green. However, the characteristics of these two ecosystems must be fully mapped out for the appropriate type of linkage to be recommended. 


Data such as plant and animal species, vertical vegetation and canopy structure, urban morphology, hydrological and meteorological factors are crucial for analysis. Only after an extensive survey can the most suitable course of action for these areas to be recommended.

– Rahim
About the writer:
Abdul Rahim bin Abdul Hamid received the B.Sc. (Chemistry and Microbiology) (1995) from the National University of Singapore, Grad. Dip. Appl. Sc (Horticulture) (1997) and Master of Landscape Architecture (2002), both from the University of Melbourne. 
After having practised as a landscape architect in Australia as well as in Singapore, Abdul Rahim is pursuing a doctoral degree at the National University of Singapore (NUS). Abdul Rahim is also a part-time Graduate Student Researcher at the Centre for Sustainable Asian Cities and a Teaching Assistant for the School of Design and Environment, NUS since 2010. 
His research interests include urban ecology, landscape ecology, GIS and environmental visualisation, environmental and landscape planning, and urban and landscape heritage.
For more information, please contact Rahim at 
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Figure 9


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