Singapore has set aside roughly 7,800 hectares of nature reserves, parks and green spaces—about 10% of the island's total land area. Yet reserves rarely exist in isolation. Between Bukit Timah in the west and the Central Catchment forests lies a physical bridge of linked canopy. Connecting these patches without interruption is what NParks describes as its ecological connectivity strategy, and it involves more than planting trees beside roads.
Henderson Waves bridge along the Southern Ridges — one of several elevated structures threading green spaces together. Credit: Wikimedia Commons
What ecological corridors actually do
A corridor, in ecological terms, is any strip of habitat that allows animals to move between two larger patches. In Singapore's case, this matters most for species such as the Sunda pangolin, the common palm civet, the long-tailed macaque and various squirrel species that require ranges larger than a single reserve can provide.
Fragmentation—the splitting of habitat by roads, drains and built structures—is one of the most documented drivers of biodiversity loss in urban settings. When a population cannot move, it cannot interbreed with neighbouring groups, access new food sources during seasonal scarcity or recolonise an area after a local extinction event. Corridors reduce all three risks.
NParks figure: Singapore's main nature reserves together harbour more than 2,000 native plant species, 400 bird species and 60 species of mammals. The corridors between them are considered part of the habitat area, not merely infrastructure.
The four main nature reserves and their links
Singapore formally gazetted four nature reserves under the Parks and Trees Act:
- Bukit Timah Nature Reserve — 163 hectares of primary dipterocarp rainforest, the highest-density forest in Singapore
- Central Catchment Nature Reserve — 2,887 hectares surrounding four reservoirs, the largest protected area
- Sungei Buloh Wetland Reserve — 202 hectares of coastal mangrove and mudflat, declared an ASEAN Heritage Park in 2003
- Labrador Nature Reserve — a smaller coastal forest on the southern shore
Bukit Timah and Central Catchment are separated by the Upper Bukit Timah Road and the KJE expressway. Since the 1990s, NParks has planted native species alongside both roads and installed what it calls eco-links—vegetated overhead crossings that allow terrestrial animals to move between the two reserves without descending to road level.
Eco-Link@BKE: the first dedicated wildlife crossing
Opened in 2013, the Eco-Link@BKE spans 50 metres over the Bukit Timah Expressway at its widest point. It was designed as an hourglass shape—wider at each end where it connects to the reserve edges—to give animals arriving at either shore a gradual transition from dense planting to the crossing surface.
Camera trap monitoring conducted by NParks recorded 22 species of animals using the link within its first few years of operation, including the Sunda pangolin, the banded leaf monkey and the common palm civet. The bridge carries more than 90 plant species, chosen to mirror the understorey and mid-canopy layers found in the adjacent forest.
Plant species selection on wildlife crossings
The selection of plants for eco-links is not arbitrary. NParks uses native species that fruit and flower at staggered intervals, providing food sources throughout the year. Ficus species in particular are valued because their fruit attracts birds and small mammals, which in turn attract the predators that use the crossing. Root architecture matters too: trees with wide, buttressed roots create microhabitats within the crossing itself, where smaller invertebrates and reptiles can shelter.
The Park Connector Network as a secondary system
The Park Connector Network (PCN) is a separate, primarily human-oriented system of paved and natural-surface paths threading through parks and residential areas. As of 2025 it covers more than 300 kilometres. While the PCN was not designed as a wildlife corridor, NParks has progressively greened its edges by planting native species and allowing naturalistic groundcover to establish along unmanicured sections.
The distinction between the PCN and true ecological corridors is important. A paved path through manicured grass provides little habitat value. The ecologically meaningful sections are those where the PCN runs adjacent to secondary forest or riparian vegetation, particularly along the Kallang River, Sungei Whampoa and the eastern branch of Sungei Bedok.
Riparian corridors along reservoirs
Water edges—reservoir margins, canal banks and tidal rivers—form a third category of corridor that often receives less attention than forest bridges. Singapore's reservoirs are flanked by vegetation buffer zones managed by NParks and PUB. The banks of Lower Peirce Reservoir, for instance, support mature secondary forest that connects directly to the Central Catchment boundary. Kingfishers, herons and smooth-coated otters move freely between the reservoir system and the larger reserve.
The Southern Ridges as an urban green corridor
The Southern Ridges is a chain of parks—Mount Faber, Telok Blangah Hill, HortPark and Labrador—connected by an elevated walkway system roughly 10 kilometres long. It is not a nature reserve but functions as a green corridor in the urban sense, supporting populations of common species such as the changeable lizard, the common flameback woodpecker and fruit bats, which use it as a movement route between the southern coastline and the central urban area.
The Henderson Waves bridge, at 36 metres above Henderson Road, is the most visible structure in the Southern Ridges chain. Its wave-shaped deck incorporates curved wooden pods that create sheltered rest areas, and its under-structure supports colonisation by ferns and climbers during Singapore's wet months.
Ongoing challenges
Despite the infrastructure, Singapore's green network faces pressures. Development along the forest edge at Mandai, in the Clementi area and along the western shore of the Central Catchment reduces the depth of the buffer between reserves and built-up land. Roadkill data collected by citizen scientists through platforms such as iNaturalist shows that several road sections—particularly along Mandai Road and Jalan Bahar—remain high-mortality zones for reptiles and small mammals despite nearby greenery.
NParks has published a Nature Conservation Masterplan and a Parks and Waterbodies Plan that identify priority areas for corridor enhancement through 2030. These include replanting of degraded secondary forest at Tengah, establishment of mangrove patches along the northern coast and vegetation of the margins of new drains in the Jurong Lake District.