A study by NUS and National Parks Board (NParks) found that tropical roof gardens in Singapore are hosts to myriad bird and butterfly species, including 24 uncommon or rare species. The research was published in Ecosphere on 7 September.
The study was led by Mr James Wang Wei, a Research Fellow with Centre for Urban Greenery and Ecology, a joint initiative by NParks and Singapore Workforce Development Agency. The research was supervised by Associate Professor Edward Webb from NUS Biological Sciences.
Explaining the genesis of the study, Mr Wang said, “My colleagues and I were drawn to roof gardens because they represent one possible solution to the dilemma of how to safeguard biodiversity conservation goals in the context of high-density urban development, which is often otherwise framed as a zero-sum game. Roof gardens in Singapore are in fact incredibly diverse in terms of environmental conditions, so we sought to understand how these could be adapted to meet the needs of some non-ground-dwelling urban fauna.”
Managed green spaces, such as roof gardens, play three important roles in urban biodiversity conservation. They assist in the movement of wildlife between otherwise isolated populations, provide consistent supplementary resources for fauna with homes within foraging distance, and act as breeding sites.
The research team identified 30 sites across Singapore for detailed study over a 20-month period. NUS Life Sciences alumna Ms Chloe Tan and Ms Vivien Lee, under Assoc Prof Webb’s supervision, conducted 20 surveys at each site.
More than 23,000 independent bird and butterfly encounters were recorded, comprising 53 bird and 57 butterfly species, accounting for 13 per cent and 18 per cent of the bird and butterfly species in Singapore respectively. Of these, 12 bird species and 12 butterfly species were considered uncommon or rare in Singapore, including the Blue Rock Thrush (Monticola solitarius) and the butterfly Tajuria dominus.
Interestingly, the roof gardens presented a diversity of species that was quite unlike gardens closer on the ground. The researchers observed a greater proportion of fruit eaters and aerial insectivores among the birds detected — this is unlike the overall bird population in Singapore, which had more carnivorous and terrestrial insectivores. Butterflies seen at roof gardens were more likely to have larger wingspans and were more mobile.
A surprising finding from the study was the fact that several roof gardens in very heavily urbanised and industrial settings demonstrated unusually high diversities of bird and butterfly species. “It seems that roof gardens isolated from other green areas in industrial and commercial districts could act as resource-rich oases for wildlife with limited other options for movement, foraging and reproduction at the ground-level,” shared Mr Wang, who is currently a PhD candidate at NUS Geography.
The researchers also identified the main factors attracting wildlife to the gardens and recommended building roof gardens that are below 50m high with at least 1,100sqm of planted area. A diverse selection of shrub species as well as appropriate inclusion of fruit and nectar plants would also have a positive impact on bird and butterfly diversity.
The research was highlighted in a speech by Mr Desmond Lee, Minister for Social and Family Development and Second Minister for National Development at the opening ceremony of GreenUrbanScape Asia 2017.
At the event, the Ventus building at NUS, whose sensitive design incorporates quality environmental features and care for the natural surrounding environment, was presented the Outstanding Project Award as part of NParks’ Landscape Excellence Assessment Framework certification, which recognises developments with outstanding greenery that enhances biodiversity. Ventus was also honoured with the Excellence Award (Educational Institution) under NParks’ Skyrise Greenery Awards, which recognise urban greening efforts.
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