The reality of animal crossings

‘Roads or borders?’ – this question posed by Chen (2017) succinctly captures the differential impact of urban developments on human and non-human inhabitants of the city. As urban developments encroach upon and intersect nature, the hybrid socio-natural spaces produced encompass variegated encounters between the two realms, with profound consequences (Swyngedouw, 1996). This is clearly illustrated in the case of urban mobility – while transport infrastructures have enabled increasingly rapid movements of people, wildlife movement have been contrastingly impeded.  

Reconnecting a divided forest

In 1986, Singapore’s central nature reserve was split into two by the Bukit Timah Expressway (BKE). The six-lane expressway runs through the centre of Singapore, dividing the reserve into the Bukit Timah Nature Reserve and the Central Catchment Nature Reserve.

Map of BKE dividing the Bukit Timah Nature Reserve (left) and Central Catchment Nature Reserve (right) (Adapted from:

While enhancing connectivity for motorists, BKE forms a physical barrier to wildlife movement. Wildlife populations were isolated, with knock-on impacts on genetic diversity and biological fitness. For instance, the common Long-tailed Macaque in Singapore’s forests separated into two sub-populations, showing signs of inbreeding depression (Chung et al., 2016).

The throngs of traffic however, did not stop all wildlife from attempting to cross the BKE, with often fatal consequences. The BKE has seen many vehicular-wildlife collisions since its construction. This includes that of critically endangered animals like the Sunda Pangolin – from 1994-2014, an average of 2 pangolins perished from roadkills (Chew and Pazos, 2015). While this number may seem small, there are only roughly 50 pangolins in Singapore (ibid).

Common roadkill victims in Singapore (Image source from left to right:,,

With growing environmental consciousness, a wildlife overpass, Eco-link@BKE, was built in 2013. Being the first of its kind in Singapore and South-east Asia, Eco-link@BKE was a major step forward in Singapore’s conservation practise – signifying a shift from merely conserving remaining nature areas to active restoration seeking to undo previous scars.

Laudably, extensive research and nature surveys were conducted to conceive the overpass’s design: including an hour-glass shape to funnel wildlife onto the overpass, and meticulously planned soil and vegetation composition.

Vegetation and soil structure of Eco-Link@BKE (Adapted from:

Positive results have been seen, with cameras sighting various wildlife crossing the eco-link, such as pangolins and palm civets.

Everlasting barriers

That said, Eco-link@BKE is by no means a panacea. Despite being designed to funnel wildlife, the overpass is ultimately only situated at a particular point along the entire intersection. With the lack of concrete barriers to prevent wildlife from getting on the road, roadkillings still occur (Wang, 2019). For instance, in 2018, a rare Sambar deer was euthanised after a collision on BKE and a pregnant wild boar tragically died along with its unborn litter of piglets.

These large mammals in particular are prohibited from using the Eco-link@BKE as they are thought to damage the Bukit Timah Nature Reserve, with the smaller forest being unable to support the foraging of large mammals. Though this decision was made for the interest of wider conservation aims, it is evident how infrastructural designs continue to control species’ (im)mobility.

Photo of fence on the overpass preventing large mammals to cross (Adapted from:

The risk of tokenism

Wildlife overpasses risk being portrayed as a magic bullet for habitat fragmentation. In the case of Eco-link@BKE, the overpass is ironically more visible to humans than wildlife, with its beautifully designed façade standing out for passing motorists (Wang, 2019).

Streetview of Eco-link@BKE (Source:,103.7838116,3a,75y,314.74h,100.72t/data=!3m6!1e1!3m4!1sR5FIPSqgAAXIgt-yJzWFsQ!2e0!7i16384!8i8192?hl=en&authuser=0)

With its heavy publicity – from widespread news coverage, grand tree-planting opening event to guided walks for the public – Eco-link@BKE is arguably more than a restoration effort but instead, a branding project promoting Singapore’s dedication to biodiversity conservation. Such an image is key to Singapore’s quest of becoming a ‘leading sustainable city’ (Wang, 2019:19).

In this sense, there lies a danger of wildlife overpasses being used to legitimise developments affecting nature areas. For instance, just opened in December 2019, Singapore’s second wildlife overpass, Mandai Wildlife Bridge, was built as a mitigation measure against wildlife displaced by the upcoming Mandai eco-tourism hub which encroaches on secondary forests. Environmentalists have criticised the move, highlighting the overpass’s inadequacies – narrow width of 30m (compared to the 50m wide Eco-link@BKE), proximity to visitor look-outs of wildlife parks and poor timing (construction of wildlife parks began in 2017, way before completion of the overpass) (NSS, 2016).

Imagining convivial urban mobilities

Evidently, the proximity of nature areas to roads have created treacherous journeys for wildlife in Singapore, exacerbated by developments encroaching upon nature areas. While wildlife overpasses have been constructed to facilitate wildlife movements across roads, perilous and often fatal animal crossings have yet to cease. Regrettably, wildlife overpasses risk becoming an ‘ethical bypass’, justifying continual appropriation of nature for urban growth (Wang, 2019:19). In line with the push for conviviality (Hinchliffe and Whatmore, 2006), it is crucial to rethink our modes of development, in order to enable the mobilities of non-human inhabitants.

[762 words]


Chen, M. (2017) ‘How effective are wildlife corridors like Singapore’s Eco-Link?’ (WWW) Menlo Park, California, United States: Mongabay ( ; 20 Nov 2020).

Chew, H.M. and R. Pazos (2015) ‘Animals Crossing Eco-Link@BKE: Safe passage for creatures over busy highway’ (WWW) Singapore: The Straits Times ( ; 20 Nov 2020).

Chung, Y.F., T.W. Wong and S. Chan (2016) ‘Eco-Link@BKE: A Safe Corridor for our Biodiversity’, CITY GREEN, 12, 92-95.

Hinchliffe, S. and S. Whatmore (2006) ‘Living cities: Towards a politics of conviviality’, Science as Culture, 15, 2, 123-138.

NSS (2016) Nature Society’s Position Paper on the Mandai Safari Park Holdings (MSPH)’s Mandai Development Plan, Singapore: Nature Society Singapore (NSS).

Swyngedouw, E. (1996) ‘The city as a hybrid: On nature, society and cyborg urbanization’, Capitalism Nature Socialism, 7, 2, 65-80.

Wang, J. (2019) ‘ReImagining Urban Movement in Singapore: At the Intersection Between a Nature Reserve, an Underground Railway and an Eco-Bridge’, Cultural Studies Review, 25, 2, 8-30.

6 thoughts on “The reality of animal crossings

  1. I really like this post. It makes me think how as humans we have caused so much harm and danger to wildlife. Something as simple as building a motorway can, in fact, be disastrous for wildlife given the segregation it can cause between species. It would be interesting if you could give your perspective as to how Singapore can deal with animal crossings, or if there is a better solution to allowing wildlife to freely move around. Could something underground be better to physically separate animals from cars?


    1. Hi Nasir, thank you for your comments! Designing appropriate animal crossings is indeed a pressing challenge – one that still requires much research but is often overlooked. With regards to your suggestion on adopting underground infrastructures that physically separate animals from vehicles, I am doubtful if such an approach is necessarily ecologically sound.

      As highlighted in my previous post (, underground infrastructures have very real impacts on fragile ecosystems. For instance, mandatory soil investigation works cause disturbances to the soil structure and vegetation, with knock on effects of soil erosion and siltation, affecting aquatic habitats in the long run. Moreover, reverberations from underground construction works and the eventual operation of the trains results in noise pollution. As such, while underground infrastructures are physically absent on the surface (literally and metaphorically), environmental impacts are very much present. In this sense, there lies the danger of the “invisibility” of underground infrastructures masking the damage to the environment, rendering these impacts “invisible” too.

      Ultimately, I would feel that the key to enabling wildlife mobilities lies in genuine attentiveness to the needs of different species. While wildlife overpasses are not the panacea, they are certainly not pointless. When well-designed (e.g. appropriate width, vegetation types, soil composition), wildlife overpasses do facilitate the movement of target species. What is then needed is a sensitivity to the range of affected species and the spatial extent of the habitat fragmentation. There has actually been some innovative animal crossings in the Mandai area which I didn’t have the chance to expand on in my post. Although the Mandai Wildlife Bridge was criticised for its inadequate planning, several rope bridges have been built apart from that overpass. These rope bridges are placed at multiple points along the road, allowing arboreal animals to cross. Here’s a video for more information: ( This example shows how animal crossings do not have to be large-scale infrastructures – simple, well-thought out solutions that consider the needs of different species can enable safe wildlife mobilities too.

      Hope this response answers your questions 😀


  2. Hi there! This was a fascinating read – the part where you pointed out that the overpass was more visible to humans than the animals it is designed for was a really neat way of drawing attention to the debate of who the overpass is designed for. Would you see this as a case of what Finewood (2016) calls “grey epistemologies” (in Week 3’s Green Infrastructure reading), and if so, how could we move away from such “grey epistemologies”? Do you feel that such overpasses will become the “standard way” of managing wildlife crossings in Singapore?


    1. Hi Yi Xin, thanks for your comments! You’ve highlighted an interesting perspective which didn’t come across my mind previously haha. When looking at the broader picture, in terms of transport infrastructures as a whole, I feel that wildlife overpasses can indeed be viewed as a case of “grey epistemologies”. Though wildlife overpasses are not directly linked to the technical systems of transport infrastructure, their role as a restoration for / mitigation against habitat fragmentation caused by roads risks legitimising existing dependence on roads as transport infrastructure.

      With regards to moving away from such “grey epistemologies”, perhaps a potential way forward is to engage and empower nature groups. For instance, the Nature Society Singapore in particular has much expertise regarding the ecologies of remaining ecosystems, as seen in their elaborate responses to the CRL and Mandai Wildlife Bridge (e.g. knowledge on types of ecosystems and micro-habitats, species assemblage from nature surveys, estimated impacts of proposed developments on ecosystems). Extending greater support and recognition to nature groups like NSS would facilitate productive collaborations between authorities and nature groups. When nature groups’ expertise are placed on par with that of technical experts leading infrastructural developments, their opinions could then be formally included into the planning process, spurring new modes of development that are inclusive to the needs of nature.

      On whether overpasses will become the standard way of managing wildlife crossings in Singapore, I don’t think I’m qualified to make such a statement since I’m not an expert in this field. Nonetheless, in my humble opinion, short of “rewilding” existing roads that cuts through nature areas, which is arguably radical and unlikely to happen in the near future, structures that allow animals to cross over roads will be most feasible. However, such overhead structures can come in many forms. For example, as mentioned in my reply to Nasir’s comments, simple and cost-effective structures like rope bridges can also be viable in enabling movement of arboreal animals such as Macaques, albeit they are very specific in the target species. Whereas for wildlife overpasses, the complex vegetation structure and size of the bridge accommodates a wider range of animals. As such, I feel that there isn’t really a standard structure since the that will depend on the target species concerned.

      Hope this response answers your questions 😀


  3. Hi! This is a topic that has such a global context! As a model solution for habitat conservation, across increasingly urbanising areas, your post really highlights how we need to think critically about these infrastructures rather than assume they are ecologically beneficial. The media and visuals you included really add to the story and my understanding of the topic, great post!

    Much of UPE study look at the underlying power structures that give an indication of the underlying motivation behind much of these initiatives. Was there an indication of specific stakeholders behind the construction which might frame the Ecolink motivated more by ‘greenwashing’ than an ecological intention? As you say an ‘ethical bypass’ is always a risk with technocratic solutions to nature-based, human-induced issues. But there is a question to whether we should criticise infrastructure which are evident to create a beneficial outcome in comparison to the baseline (as evident in your video link), for productive change.


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