We’ve all heard and talked about Singapore’s nature reserves, nature parks and park connectors. But what about nature ways? I asked three of my BES friends recently and none knew what they are. Alas, these important but rather inconspicuous green corridors have rarely been given a mention: there isn’t even a sign to inform people that they are walking along one! Another reason for their low profile may be their scarcity: there are just 16 in total spanning a relatively short total distance of 68 km (Fig. 1.). Compare that to Singapore’s 78 park connectors totalling 300 km in length (Abdullah, 2015)!

So…what is a nature way?

Just by looking at Fig. 1, the nature ways resemble park connectors but they couldn’t be more different! Many park connectors meander through housing estates and are equipped with user-friendly facilities, such as benches, shelters, cycling tracks and even exercise corners. However, most nature ways are more like enhanced roadside streetscapes (they run alongside roads) and they lack user facilities. Additionally, unlike most park connectors (or nearly anywhere else for that matter) which are planted with trees of the same species and at uniform heights (urban monocultures) to present a “neater” and “orderly” image, nature ways are intentionally planted with a wide variety of plant species and have a more layered vegetation structure to mimic a forest as closely as possible (NParks, n.d.-a) (Fig. 2).

Function and importance of nature ways

Why develop nature ways? Well, nature ways are important as they help restore ecological connectivity between fragmented green patches in highly urbanised Singapore. By more closely replicating natural forests, nature ways attract a variety of animals that use them as habitats and wildlife crossings. Animals including birds, reptiles, amphibians, and invertebrates (that occupy different layers) are thus, able to move between green spaces of high biodiversity (NParks, n.d.-a). This facilitates gene flow and dispersal of animals, which are important to reduce inbreeding in otherwise isolated population (Angold et al., 2006).

For example, the longest one, Tengah nature way (TNW), links Bukit Timah Nature Reserve, Central Catchment Nature Reserve and the Western Catchment (NParks, n.d.-b). Surveys conducted to assess its effectiveness found forest-edge species, such as the horsfield’s baron butterfly and common gliding lizard, which were rarely seen before at that location (Chua, 2015), suggesting that the TNW was attracting more animals and facilitating their crossings.

Are there areas for improvement in terms of the design and development of nature ways?

Though nature ways are developed with well-intentions, I feel that there are areas which can be improved. Some of the nature ways (especially long ones like TNW) are not continuous, but occasionally separated by artificial barriers, such as road junctions. This could hinder the movement of animals that are road-phobic and would avoid crossing even the narrowest of roads. Indeed, numerous studies have documented road avoidance behaviour or reluctance to live close to the roads in many animal species, including birds, insects, and mammals (Laurance et al., 2009; Muñoz et al., 2015). Even if the animal does decide to cross the road, it would have to face an onslaught of vehicle traffic and risk being hit by one, which could lead to road mortality. Therefore, it would be better if nature ways could avoid road crossings altogether, but I can only assume that because nature ways should link one green space to another, NParks would have already planned the configuration of nature ways to minimise road crossings.

Additionally, vegetation in some parts of the nature ways is sparse and often sandwiched between the road (some of which have heavy traffic) and pedestrian path (Figs. 3 and 4). This could influence the abiotic conditions in nature ways, resulting in warmer and drier microhabitats as compared to forests because of greater exposure and proximity to impervious surfaces. Noise (vehicles and pedestrians), light (from public street lighting) and air pollution (vehicular emissions and dust) will also reduce the quality of these roadside habitats. Therefore, different environmental conditions compared to natural habitats could deter some species from using the nature ways as crossings or habitats. To reduce these effects, more plants should be planted especially in vegetation-sparse areas to increase vegetation density and improve the quality of re-created habitats along nature ways.

 

Finally, I came across a paper by Jain et al. (2014) which argue that the existing method of merely planting bird- and butterfly-attracting species capable of withstanding roadside conditions is inadequate. Instead, planners should also consider the ecological needs of species found in the source and sink fragments before deciding on the types of flora to plant along nature ways (Jain et al., 2014). I concur with the authors, as based on my experience walking along the nature ways, I seldom see a great variety of fauna, and one reason could be the incompatibility of plant species to the fauna found in the connected habitat patches, which deters them from using the nature ways.

Final thoughts

Overall, I am all for the development of nature ways as a habitat de-fragmentation strategy to connect various urban green spaces and conserve Singapore’s biodiversity. The good news is that NParks aims to increase the total length of nature ways to 180 km by 2030 (NParks, n.d.-a)! I do hope that they consider the areas for improvement (as mentioned above) during the development of new nature ways in the future. Also, wouldn’t it be great if park connectors (and other green strips) also adopted the layered vegetation structure and are lined with a wider variety of plant species? That could attract even more wildlife and, in so doing, foster closer connections between people and nature in an urban environment. Finally, I could find very few publicly-available research papers or data on the effectiveness of nature ways, with suggestions for improvement. Perhaps NParks conducts its own internal evaluations, but I do see a lot more room for study (ps. potential FYP topic for anyone who’s interested!).

References

Abdullah, Z. (2015, September 21). Singapore park connectors reach 300km at 25-year mark. The Straits Times. Retrieved from http://www.straitstimes.com/singapore/singapore-park-connectors-reach-300km-at-25-year-mark

Angold, P. G. et al (2006). Biodiversity in urban habitat patches. Science of the Total environment, 360(1), 196-204.

Chua, G. (2015, January 23). How Singapore makes biodiversity an important part of urban life. Citiscope. Retrieved from http://citiscope.org/story/2015/how-singapore-makes-biodiversity-important-part-urban-life

Jain, A. et al (2014). Moving away from paper corridors in Southeast Asia. Conservation Biology, 28(4), 889-891.

Laurance, W. F. et al (2009). Impacts of roads and linear clearings on tropical forests. Trends in Ecology & Evolution, 24(12), 659-669.

Muñoz, P. T. et al (2015). Effects of roads on insects: a review. Biodiversity and conservation, 24(3), 659-682.

National Parks Board (NParks). (n.d.-a). Nature Ways. Retrieved from https://www.nparks.gov.sg/gardens-parks-and-nature/nature-ways

National Parks Board (NParks). (n.d.-b). Singapore’s longest green corridor will enhance biodiversity in the South West District. Retrieved from https://www.nparks.gov.sg/news/2014/2/singapores-longest-green-corridor-will-enhance-biodiversity-in-the-south-west-district

Over the last 30 years, the world’s urban population has been rapidly increasing and is forecasted to reach nearly 5 billion by 2030 (Seto et al., 2012). This has been accompanied by rapid urban land expansion, which is occurring on average twice as fast as urban population growth (Seto et al., 2012). Therefore, if current urban population growth rates remain unchanged, urban land cover is expected to triple in size by 2030 (Seto et al., 2012). This increase would exacerbate biodiversity loss due to even more habitat fragmentation and altered local climates, among other things. However, cities still support some species and can make efforts to conserve them. How then, should cities protect urban biodiversity and ensure their efforts are making progress? Thinking along those lines, I recalled reading a publication by the Centre for Liveable Cities (CLC) (where I used to intern) that discussed biodiversity conservation efforts in cities. Two words caught my attention: “Singapore Index”.

What is the Singapore Index (SI)?

No, this is not about Singapore’s financial stock market. Instead, it involves taking stock of biodiversity in cities. As the name suggests, the SI (also known as City Biodiversity Index) was conceived in Singapore! First proposed at the Conference of Parties (COP) to the Convention of Biological Diversity (CBD) in 2008, the SI is a self-assessment tool with a scoring system for cities to measure and evaluate their progress in biodiversity conservation by comparing with a baseline year (Chan et al., 2014). In 2010, the SI was formally endorsed by the COP (Kohsaka et al., 2013). With the SI, cities can benchmark their progress in reducing the rate of biodiversity loss in urban environments, measure their ecological footprints and identify gaps in biodiversity information (Rodricks, 2010).

In short, it consists of two components (Chan et al., 2014):

• “Profile of the City” which includes background information of the city
• 23 indicators in three categories: (1) native biodiversity in the city; (2) ecosystem services provided by biodiversity in the city; and (3) governance and management of biodiversity in the city.

To know more about the SI and indicators used, you can read the user’s manual here! However, if reading a lengthy document doesn’t appeal to you (I totally understand), check out these two videos (will embed), where Dr Lena Chan, Director of the National Biodiversity Centre (NBC) under the National Parks Board, explains how the SI works and why it is useful:

Implementation of the SI

Unsurprisingly, Singapore was one of the first to implement the SI. How did Singapore fare? Not too bad! She scored well in governance, but could improve in terms of ecosystem services and freshwater supplies (Tok, 2011). Other cities have also implemented the SI, including 14 in Japan, India’s Mira Bhainder and Canada’s Edmonton (Kohsaka et al., 2013). However, there were some challenges when it came to implementation. After all, no two cities are exactly alike. Challenges include no clear definition of what defines a “natural area” and “fragmentation”, lack of data on native and invasive species, and difficulties in (1) calculating ecosystem services and (2) determining how much budget to allocate to general environmental causes and biodiversity-specific activities (Kohsaka et al., 2013).

For example, Yokohama is Japan’s second-largest city, making regular comprehensive surveys of biodiversity and terrestrial ecosystems difficult to conduct and seen as unrealistic due to budget constraints (Kohsaka et al., 2013). Indeed, lack of biodiversity data and financial constraints are major challenges in applying the SI especially for cities in developing countries. Even Edmonton, Alberta, Canada, received a relatively low biodiversity and ecosystem services score (Kohsaka et al., 2013). However, one must consider the climate (Edmonton is cold!). This is a reminder that caution should be exercised when comparing scores across cities.

Final thoughts

Overall, despite inevitable compatibility issues with the SI, I feel that it is still a useful tool. Cities may choose to add indicators to the SI or even be inspired to create their own indices to best suit their contexts. Ultimately, the main takeaway is that there is no “one size fits all” index, because it is nearly impossible to include indicators that all cities will have data on. Make it too broad, and the SI will lack depth. Make it too specific or rigid, and it will lack flexibility and applicability. At least the SI recognises the importance of biodiversity in urban environments and spurs cities to keep track of their conservation efforts, a crucial element in the pursuit of sustainable urban development.

References

Chan, L. et al (2014). User’s Manual on the Singapore Index on Cities’ Biodiversity (also known as the City Biodiversity Index). Singapore: National Parks Board, Singapore.

Kohsaka, R. et al (2013). Indicators for management of urban biodiversity and ecosystem services: city biodiversity index. In Urbanization, biodiversity and ecosystem services: challenges and opportunities (pp. 699-718). Springer Netherlands.

Rodricks, S. (2010). Singapore City Biodiversity Index. Retrieved from http://www.teebweb.org/wp-content/uploads/CaseStudies/Singapore%20City%20Biodiversity%20Index.pdf

Seto, K. C. et al (2012). Global forecasts of urban expansion to 2030 and direct impacts on biodiversity and carbon pools. Proceedings of the National Academy of Sciences, 109(40), 16083-16088.

Tok, C. (2011). City Biodiversity Index. Retrieved from http://eresources.nlb.gov.sg/infopedia/articles/SIP_1765_2011-02-11.html