Ecological connectivity between western water catchment and central nature reserves

Why is it so important to conserve Tengah forest and Bukit Batok hillside park (BBHP) area?

Why was the recent disruption of wildlife corridor between Bukit Batok nature park and Toh Tuck forest caused by excessive tree-cutting for road widening so serious?

And why do we need to protect Pang Sua woodland along Green Rail corridor from housing development?

One main reason is “ecological connectivity”.

How the connectivity along Bukit Batok nature corridor risks further disruption to wildlife movements. (Source: NParks, 99.co, Our Singapore Facebook page)

Due to rapid deforestation and urbanisation in the past two centuries, there is only one contiguous forest left that can provide safe movements of wildlife between western water catchment and central nature reserves,

which include critically endangered Sunda pangolins, leopard cats and straw-headed bulbuls, globally endangered long-tailed macaques, and uncommon Malayan colugo,

and that contiguous forest is Tengah forest.

Imagine pangolins, macaques and wild boars being able to move safely from Tengah forest to Gombak park and then to Bukit Gombak forest, and vice versa. (Photo by Jimmy Tan)

The challenge is: how can these wildlife still travel across Tengah forest safely in order to ensure healthy genetic exchange and prevent inbreeding and extinction?

Currently, there are 3 conduits between central nature reserves and Tengah forest:

1. Via Bukit Mandai, Pang Sua woodland, Bukit Gombak forest and Gombak park
2. Via Bukit Timah nature reserve, Bukit Batok nature park, Bukit Gombak forest and Gombak park
3. Via Clementi nature corridor, Bukit Batok nature park, Bukit Gombak forest, Bukit Batok central nature park and Bukit Batok hillside park (Hill 1 & Hill 2)

This is why we need eco-links to

• connect Tengah forest west to Jalan Bahar forest
• connect Tengah forest east to Gombak Park
• connect Tengah forest south to Bukit Batok hillside park

Routes 1 and 2 may be a bit tricky as the military area has barbed wire fences, which may impale colugos if they happen to land on the fences.

Wild boar tracks at Bukit Gombak forest. The barbed wires on top of the military fence may pose a danger for the Malayan colugos. (Photo by Jimmy Tan)

Route 3 is also challenging, as more trees need to be planted along roads in residential areas to create safer passages.

The forests in BBHP area along Route 3 also risk further clearance for housing development, which will disrupt ecological connectivity even more.

Any further disruption in the ecological connectivity along Bukit Batok nature corridor (and Tengah nature way) may result in irreversible damage to the biodiversity and loss of species, adversely affecting ecological functions.

Top: Aerial view of Bukit Batok hillside park (Hill 1) showing its proximity to Tengah forest on the right. Bottom: Bukit Batok hillside park (Hill 2) is essential for connecting BBHP Hill 1 and Bukit Batok central nature park. (Photos by Jimmy Tan)

Already, we have lost native species, such as the giant cream-coloured squirrel and forest gecko, when the Bukit Timah expressway construction separated Bukit Timah nature reserve from Central catchment area since the 1980s-1990s.

The stakes are high for the ecological connectivity between western water catchment and central nature reserves too.

Different forest-dependent wildlife species are affected by habitat fragmentation and disruption of ecological connectivity to varying extents. (Photo by Jimmy Tan)

Though strong dispersers among aerial and canopy wildlife, such as changeable hawk-eagles and long-tailed parakeets, are able to fly long distances, they face the threat of habitat loss, which means fewer sites for nesting, breeding and feeding.

Moderately strong dispersers among canopy wildlife, such as straw-headed bulbuls, will be affected by even small-scale deforestation, such as a planned 4-ha BTO (Build to Order) site in BBHP area.

Weak dispersers among forest-dependent wildlife, such as red jungle fowl, Sunda colugos and possibly red-legged crakes, will be most affected by any disruption of ecological connectivity, as they seldom travel far from forest edges.

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