Cross Island Line Impacts on Biodiversity in Central Catchment Nature Reserve

In the previous article, we highlighted the potential negative impacts on avian biodiversity if plans for the construction of Cross Island Line (CRL) were to follow through. In this update, we turn our focus to other biodiversity groups that reside in the MacRitchie forests - the non-avian fauna and often overlooked flora of the Central Catchment Nature Reserve in Singapore. By Tan Hui Zhen and Shermaine Wong.

Singapore, 6 July 2014. The Singapore government has announced plans to build a 50km Cross Island Line that will span Changi to Jurong Industrial Estate, targeted for completion in 2030. This line cuts through a core nature reserve at the heart of the island state that has already lost most of its natural greenery including forests due to development.

The government has heeded to calls by naturalists and NGOs to conduct an Environmental Impact Assessment (EIA) before proceeding with its plans to build the line. It has appointed Environment Resources Management (S) Pte Ltd to assess such impacts with effect from 4 July 2014.

Apart from being home to avian species, the Central Catchment Nature Reserve (CCNR) in Singapore is home to some 44 mammals, 72 reptiles, 25 amphibians and all 34 remaining native freshwater fish species. Majority of these species are forest dependent and have adapted to surviving in the CCNR.

The small Horsfield's Flying Squirrel Iomys horsfieldii davisoni, for example, feeds largely on the leaves and fruit of the primary and secondary forests at CCNR. The MacRitchie forests are also a refuge for internationally-threatened species like the Malayan Pangolin Manis javanica.

The small Horsfield's Flying Squirrel is a mammalian inhabitant of the CCNR and has been observed in larger numbers in regrowth forests. Photo by Marcus Chua.The forests hold a rich store of biodiversity that has yet to be fully discovered such as the elusive swamp skink, which was sighted at a stream near the proposed CRL alignment for only the second time in local history. There are also 25 indigenous amphibian species in Singapore, of which 18 are forest species. The MacRitchie forest supports majority of the forest frog species due to its pristine streams and primitive forest.

These rich specimens of biodiversity may be stressed with the intrusion of human activity by way of soil investigation, which is the initial step that has to be taken if works for the CRL were to be carried out.  Silt and pollutants are envisaged to be released into these streams.

Apart from soil investigation works, other surface works for the CRL works are expected to be carried out. These include the clearing of forest and soil compaction with possible impacts of toxic material spillage, erosion and siltation due to excavation. These activities are likely to contribute to the loss of one of the most pristine stream ecosystems in the CCNR.

As Mr Tony O’Dempsey, Chairperson of the Nature Society Singapore Vertebrate Study Group, aptly describes, “The Nature Society is most concerned for the fragile stream habitats, the streams that run through the MacRitchie forest are amongst the most pristine in Singapore and host a diverse range of insects, fishes, and amphibians besides providing a life-giving water source to higher mammals, reptiles and birds. Our specific concern is that soil testing activities, which will involve the construction of access roads and placement of boring machines along the proposed alignment, presents a high risk of siltation due to storm run off as well as the potential for spillage of highly toxic hydrocarbon chemicals that would leach into the streams with deadly consequences.”

A major stronghold of an internationally-threatened species - the Malayan pangolin (or the Sunda pangolin) in MacRitchie. Photo courtesy of Nick Baker.Forest streams support many specialised aquatic and semi-aquatic animals, which include locally threatened vertebrates like native turtles, terrapins, and fish, to name a few. Additionally, native freshwater fish such as the Malayan Pygmy Rasbora Boraras maculates are only found in the MacRitchie streams and the Nee Soon Swamp Forest.

It is important to note that the above vertebrate species, together with the others mentioned in the Nature Society of Singapore (NSS) position paper, play essential roles in forest ecology as predators, herbivores and seed dispersal agents as well. These ecological relationships are intricately linked in the forest ecosystem.

The loss of any species can have significant repercussions. For instance, a population explosion of opportunistic omnivores like the wild boar has followed the loss of large predators in the fragmented forests of Singapore. The growing wild boar population in turn has ramifications on the health of the forests. The digging by wild boars negatively affects forest regeneration as tree saplings are extensively destroyed.

Significantly, the proposed CRL runs through the largest patch of Primary Lowland Dipterocarp forest in Singapore and is surrounded by the oldest regenerating forest patch in Singapore. This forest patch not only contains pioneer species like Rhodamnia cinerea (silverback) and Adinandra dumosa (tiup tiup), but also saplings of primary forest species. In view of the rich understorey vegetation that the forest plot supports, NSS has highlighted that it is imperative that the forest is protected and left to regenerate. With time, it can grow in structural complexity and support greater fauna biodiversity.

There will be major and irreversible impacts on the forest ecology if construction of the CRL were to be carried out. Therefore, as the NSS position paper posits, ecosystem and services valuations have to be included in the overall cost analysis of the CRL project. It is common for economic valuations of irreplaceable nature spaces to use the ‘replacement cost’ method as a form of valuation. Due to the limited available land and technical ability to recreate such unique habitats, the cost of ecosystem and ecosystem services lost due to the CRL is expected by the NSS to dwarf the acquisition of a space of comparable land area.

Since the Land Transport Authority (LTA) called for a tender to undertake an Environmental Impact Assessment (EIA) and engaged in an eight-month long discussion with nature groups, there has been a growing consciousness of the importance of such studies in informing developmental projects. It is a heartening trend and positive progress in the right direction.

The importance of conserving our natural environment is summed up by NMP Faizah Jamal, a staunch advocate for the environment, “Without the environment, there will be no platform for the arts, sports, businesses, jobs and economy.”

Thus, it is essential that citizens realise the importance of appreciating and protecting our natural heritage - the ground on which the rest of our nation is built upon.

Images courtesy of Nick Baker and Marcus Chua.

Read the preceding Gaia Discovery article on Cross Island Line impacts on the Central Catchment Nature Reserve.

About the authors:

Tan Hui Zhen hails from the island city-state Singapore. She majors in Environmental Geography at the National University of Singapore and is interested in environmental conservation, natural resource management and sustainability issues. She hopes to learn scuba-diving and explore the colourful underwater world of our blue planet.

Shermaine Wong is based in Singapore. She has a fascination with both the built and natural environment. She is an Environmental Studies undergraduate majoring in Environmental Geography and minoring in Aquatic Ecology. Her interests are in reading, writing, photography and travelling. One of her life goals is to produce an environmental documentary. 

Edited by Mallika Naguran