Environmental Baseline Study (EBS) for Dover Forest

The Environmental Baseline Study (EBS), commissioned by the Housing & Development Board (HDB) and conducted by AECOM, provides a comprehensive assessment of Dover Forest's ecological and environmental significance before its clearance for urban development.

The study aimed to evaluate the diversity of flora and fauna, hydrological conditions, and the overall environmental health of the area to guide development plans while addressing conservation concerns.

The Environmental Baseline Study for Dover Forest highlighted significant impacts resulting from the clearing of the site for residential development. These include irreversible changes to biodiversity, hydrology, and ecosystem functions.

Loss of Vegetation and Habitat

Vegetation Types

The study identified 12 vegetation types within Dover Forest, which included:

Abandoned Land Forest (49.25%): Comprising plantation remnants (Hevea brasiliensis) and kampung-derived forest with mature fruiting and decorative trees.
Native-dominated Secondary Forest (8.78%): A mix of early successional species, including Macaranga gigantea and Ficus fistulosa.
Riparian Vegetation (1.41%): Found near streams and drainage lines, crucial for water filtration and aquatic ecosystems.

The clearance led to:

Permanent loss of approximately 91.2% of secondary forested areas and other vegetation types.
The removal of rare native-dominated vegetation patches that could have supported natural regeneration of native flora.

Conservation-Significant Flora

Among the surveyed flora, 12.5% were classified as threatened. This included:
- Critically endangered species such as Ficus virens (with a girth of 1,099 cm).
- Mature Aphanamixis polystachya (endangered) and Durio zibethinus (durian trees), remnants of historical kampung cultivation.
Large significant trees, crucial for carbon sequestration and habitat provision, were removed during clearance.

Loss of Faunal Habitats

The forest supported 158 faunal species, including:

82 bird species: Notable species like the Changeable Hawk-Eagle (Nisaetus cirrhatus) and Violet Cuckoo (Chrysococcyx xanthorhynchus), which are classified as endangered or vulnerable.
8 mammal species: Including the Sunda Pangolin (Manis javanica), a critically endangered species in Singapore.
11 reptile species and 8 amphibian species, many of which rely on riparian zones and secondary forests.
Aquatic fauna: Streams within the forest provided habitats for rare native Apple Snails (Pila scutata) and other aquatic invertebrates.

The forest's role as a wildlife corridor was diminished, disrupting species movement and reducing overall habitat connectivity. The presence of forest specialists like the Glossy Swiftlet (Collocalia esculenta) underscored the importance of the area for ecological diversity.

Hydrological Impacts

The EBS identified critical hydrological features within the site:

Streams and Drainage: Four earth streams and one canal (Ulu Pandan Canal) ran through the forest, contributing to stormwater management.
- Stagnant water in some streams supported unique aquatic biodiversity, but clearance disrupted these habitats.
Water Quality: Streams originating from dense vegetation showed better oxygenation and lower temperatures, essential for maintaining aquatic life.

The clearing of forest vegetation increased surface runoff, sedimentation, and potential flooding risks in nearby areas, reducing the effectiveness of natural water filtration systems.

Decrease in Ecosystem Services

The study emphasized Dover Forest's contributions to:

Carbon Sequestration: Mature trees, especially large ones like Ficus virens, provided substantial carbon storage. Their removal reduced local carbon absorption capacity.
Temperature Regulation: Dense canopy cover helped cool the microclimate, mitigating urban heat. The clearance heightened the urban heat island effect.
Pollution Filtration: Vegetation played a critical role in improving air quality by filtering particulates and pollutants, which is now lost.

Vegetation Condition and Degradation

Based on vegetation condition assessments:

44.95% of the forest was classified as "Good," retaining all vegetation layers with diminished species richness.
Only 0.75% was rated "Very Good," consisting of rare native-dominated forest patches.
43.81% of the site was already degraded due to historical land use, but further clearing exacerbated the loss of ecological potential.

Species-Specific Impacts

Monodominant Forest Areas: The dominance of species like Hevea brasiliensis (rubber trees) and Falcataria moluccana reflected the forest’s history as an abandoned plantation. These areas, while less biodiverse, provided a refuge for fauna.
Edge Effects: Clearing activity increased edge effects, promoting invasive species like Mimosa diplotricha and reducing habitat quality for native flora and fauna.