My feedback to HDB on Environmental Baseline Study report regarding Choa Chu Kang N1 (including Pang Sua woodland and river canal)

Aerial view of Pang Sua woodland and river canal, which are flanked between the built-up areas of Choa Chu Kang (background) and Bukit Panjang (foreground) housing estates (Photo by Jimmy Tan)

Here is my feedback on Housing and Development Board (HDB)’s Environmental Baseline Study (EBS) report for Choa Chu Kang N1, which includes Pang Sua woodland and river canal, in Singapore.

I understand that this forest patch is one of the few sizeable natural habitats (which include Kranji woodland, Clementi forest and Alexandra woods) located along the long and narrow 24-km Green Rail Corridor.

These core forest habitats are vital for native wildlife, such as critically endangered Sunda pangolins, common palm civets and wild boars, to rest, roost, forage and take refuge from apex predators, human disturbance and noisy motor traffic, otherwise they will be exposed to danger in open spaces and may also end up wandering into urban spaces and becoming roadkills or getting involved in human-wildlife conflicts.

(The above video records a sighting of a wild boar (whose species is invaluable for tree seed dispersal and regeneration of tropical forests) along the Green Rail Corridor between Pang Sua woodland and Kranji woods in February 2021. As noted in my feedback to NParks, wild boars are sensitive to disturbances of their natural habitat, which may force them to wander into residential areas. In 2017, a wild boar was involved in a conflict with a human being before it got into a fatal road accident in Hillview, about 2 km south of Pang Sua woodland.)

The EBS report noted that the “original vegetation at the Study Area was likely to be a mangrove swamp forest which was subsequently cleared for rubber plantations”. Since mixed vegetation, comprising mainly mature trees and shrubs, currently occupies around 15 ha of the study area, we should conserve and restore the forest to what it originally was as closely as possible, by naturalising Pang Sua canal and rewilding the woodland and Green Rail Corridor, in order to recreate a mix of lowland secondary forest and freshwater swamp forest (since the water in the canal is no longer saline after Kranji river has been dammed to form a reservoir).

This is because besides providing climate resilience and ecological connectivity, Pang Sua woodland is also a sanctuary for human residents and visitors to seek relief from the heat and stress of urban living that affects physical health and mental well-being.

Pang Sua woodland receives strong support from Nature groups, such as Nature Society (Singapore), Cicada Tree Eco-Place and Lepak in SG, as well as Nature enthusiasts, to be conserved for ourselves and our future generations.

Taking into consideration the official responses to public feedback on the Environmental Impact Assessment (EIA) reports regarding recent planned housing development projects in greenfield sites, such as Bukit Batok hillside park area and Dover-Ulu Pandan forest in 2020-2021, I would like to address possible objections or questions concerning the conservation and restoration of Pang Sua woodland, which is proposed by Nature groups and Nature enthusiasts, including me.

1. Is Pang Sua woodland still worth conserving since it isn’t near any nature reserve in Singapore?

As shown in the map below, Pang Sua woodland is a core habitat located at the Green Rail Corridor (as also noted in the EBS report). It is connected to Tengah forest and Western water catchment via Hillview and Bukit Gombak within 2-3 km in the south. It is also connected to Kranji woods and Sungei Buloh wetlands reserve, Kranji coastal nature park and Mandai mangrove mudflats in the north. To the northeast, it is linked to Bukit Mandai (within 2-3 km) and Central catchment nature reserve.

Pang Sua woodland functions as a critical ecological corridor to ensure safe movements of native wildlife species, including critically endangered Sunda pangolins and straw-headed bulbuls, between Western water catchment and Central catchment nature reserve. Without such ecological connectivity, having rare and endangered species (such as mousedeer, Sambar deer and Raffles banded langurs, which may one day use these green corridors too) confined to Central catchment nature reserve is like putting all the eggs in one basket, where the threatened species risk experiencing population decline and extinction, due to factors such as inbreeding, climate change accelerating tree mortality, lack of healthy genetic exchange, etc. (Photos by Jimmy Tan)

2. Should Pang Sua woodland be conserved fully as it doesn’t seem to have very much biodiversity?

Critically endangered pangolins have been seen using Pang Sua canal and woodland as an ecological corridor, which may also be used by straw-headed bulbuls as a stepping stone. It is a vital conduit to ensure their safe movements and healthy genetic exchange so as to sustain their existence in the long term. Even the common species, such as rain trees (Samanea Saman), serve as shelter and provide food for less common species.

Although rain trees are common non-native species, they support the growth of epiphytes and provide food and shelter for wildlife. As also noted in Tengah North Environmental Impact Studies (EIS) report (page 185), “it is important to recognize that both common and rare species contribute ecological functions in an ecosystem.” (Photo by Jimmy Tan)

Incidentally, the pangolin is one of the six indicator species identified in NParks’ island-wide ecological profiling exercise, which were selected “as they are sensitive forest dwellers that may venture out to forest edges, provided suitable habitat is created for them there”.

It is noteworthy that after Singapore authorities conducted massive seizures of pangolin scales in 2019, “NParks said the authorities take a zero-tolerance stance on the use of Singapore as a conduit to engage in illegal wildlife trade, as well as the illegal sale or keeping of wildlife”.

Even as Singapore’s strict enforcement of the ban of international trade of pangolins is commendable and should be applauded, it seems contradictory that our local pangolin population continues to face the risk of habitat loss, degradation and fragmentation, as well as roadkills, due to ongoing urban encroachment which threatens their existence and safe movements in core habitats and wildlife corridors, such as Tengah forest and Pang Sua woodland.

The Singapore Pangolin Working Group noted that “Sunda pangolins are mammals native to Singapore and are classified as Critically Endangered in the Singapore Red Data Book 2008 as well as the IUCN Red List of Threatened Species. Their main threats in Singapore are habitat loss and alteration, as well as road traffic accidents — this contrasts with the major threats that this species is facing regionally, which include poaching and the illegal wildlife trade. Singapore is not losing its forests as fast as its neighbours, but the slow creep of urbanisation continues to shrink the patches of forest pangolins depend on for food and shelter.” (Photo by Jimmy Tan for illustration)

3. Isn’t there a strong demand for public housing, and shouldn’t human needs come first instead of nature conservation?

Regardless of the reasons for a strong demand for public housing, brownfield sites (such as old or underutilised industrial sites, abandoned schools, open car parks, golf courses whose leases are expiring soon, old HDB flats nearing their 99-year lease that can undergo Selective En Bloc Redevelopment Scheme (SERS) or Voluntary Early Redevelopment Scheme (VERS) as early as possible, etc) should be prioritised over greenfield sites for housing development or redevelopment projects. For example, the heavy vehicle carpark and defunct bus terminal near Pang Sua woodland can be recycled to build tall Build-To-Order (BTO) flats. Also, human needs aren’t restricted to just housing, but also physical health and mental well-being. Since Singapore is already heating up twice as fast as the rest of the world, it would be detrimental to one’s health and well-being in the long run when one lives in a highly built-up area in hot sweltering conditions, even if it is within 10 minutes’ walk to small pocket parks, as they can hardly cool the urban heat island effect in the surroundings.

According to studies, a large forest of an area of 10 ha or more (such as Pang Sua woodland) can cool the surroundings by 1-2 degrees Celsius up to a distance of 350 metres, whereas plants on building facades can only cool up to 4 metres. The denser the foliage, the greater the transpiration and cooling effect of the forest (and the more it can help residents reduce electricity bills by relying less on artificial air-conditioning). (Photo by Jimmy Tan)

4. Hasn’t the Urban Redevelopment Authority (URA) master plan 2019 already designated Pang Sua woodland for housing development many years ago?

Much as we appreciate the efforts made by urban planners, we also need to acknowledge the fact that urban planning 10 or 20 years ago was different from today’s context. Back then, urban planners weren’t required to take a course on basic ecology and the EIA process, so they might not have taken habitat fragmentation and climate crisis into consideration adequately. The Climate Action Tracker has considered Singapore’s climate policies and actions to be highly insufficient as of July 2020. The Intergovernmental Panel on Climate Change (IPCC) has also declared Code Red for the climate emergency in 2021. We cannot afford to adhere rigidly to the master plan if we want to be responsive to be more climate resilient and prevent biodiversity collapse.

Climate resilience and biodiversity protection are urgent needs in the post-pandemic era we live in. Lama El-Hatow, an environmental and social consultant, showed an illustration “where future crises were represented in tsunami waves, each bigger than the one before it. She explained that once COVID-19 (the first wave) comes to an end, economic recession, climate change, and biodiversity collapse will follow”. (Illustration from The Cairo Review)

5. Should we not consider this issue as a zero-sum game, but rather consider how conservation and development can be done in tandem to have a certain balance, such as by replacing forest loss with replanted trees?

We can achieve that balance by prioritising the recycling of previously developed lands. It takes decades for newly planted trees to grow and mature to be able to provide the same level of ecosystem services and biodiversity support as the existing mature trees, so forest conservation needs to take precedence over tree planting, inasmuch as the latter is also important.

For example, Pang Sua woodland functions as a natural “rain garden” to absorb rain and purify surface runoff and groundwater flow that goes into Pang Sua river.

The river flows into Kranji reservoir, where the water will be treated before it is transported to residential and industrial areas.

The healthy riverine ecosystem downstream of Pang Sua river canal testifies to the water purifying and life-giving effect of Pang Sua woodland, which serves as a natural rain garden. (Photos by Jimmy Tan)

Such essential ecosystem services are provided by Pang Sua woodland free of charge.

Hence, conserving the forest would be a cost-effective and self-sustaining nature-based solution to ensure water security, rather than removing the forest and replacing it with man-made rain gardens which will cost a lot of time and resources.

Then again, that might well be a pipe dream that would only come true in an ideal or enlightened world.

This is because if we continue to subscribe to the environmentally destructive capitalistic economic system that prioritises Gross Domestic Product (GDP) growth over ecological health, then we will be tempted to justify clearing the trees to sell the land to developers, and give more business to architects, landscaping companies and property agencies.

After all, these companies look to the government for new development projects in order to earn profits too.

(A case in point: property agencies were quick to chime in after the government announced their response to public feedback on the Environmental Baseline Study for Dover-Ulu Pandan forest in end July 2021.)

We will also be tempted to justify using public funds to plant a man-made rain garden to replace the existing woodland and then credit it to our national efforts to transform Singapore into a “City in Nature”.

While we are at it, we might as well also spend more public funds to research, design and build carbon capture machines to offset carbon emissions, and then pat ourselves on the back for being able to do the job (albeit at great costs to the ecosystem) that Mother Nature has been doing for us for free.

Surely by creating (preventable) problems through incessant deforestation and urbanisation in order to solve them using expensive technology, we can then profess to achieve our Key Performance Indicators (KPI) and present Singapore as a smart and sustainable nation?

Or should we be working towards the implementation of a less resource-intensive and more sustainable and equitable economic model that actually respects ecological boundaries and connectivity, instead of finding ourselves gravitating towards greenwashing while heading towards self-destruction?

Spiders, frogs, geckos and dragonflies are some of the natural predators of mosquitoes. Once a forest is cleared to make way for concrete buildings and roads, the warmer microclimate and loss of natural predators tend to allow mosquitoes to breed profusely and spread dengue virus. Aedes mosquitoes thrive in highly disturbed greenery, construction sites and urban areas, where they lay eggs in warm stagnant water uninhabited by their natural predators. Fogging or fumigation has shown to be not very effective in controlling the mosquito population, and instead tends to make them more resistant and harder to kill. There is currently a rise in dengue fever cases, and it is imperative that we conserve and restore our natural ecosystems, in order to experience good ecological health and mitigate the disease outbreak effectively. (Illustration from Philippe Birker)

6. Isn’t it a fact that Singapore is a small island-state and doesn’t have a large hinterland like bigger countries?

Yes, it is precisely because Singapore is a small tropical island that it should be respected for originally having tropical rainforests and mangrove forests that are best suited to the hot, wet and humid equatorial climate, instead of being dominated by the increasing number of buildings and roads that are worsening the urban heat island effect virtually every year.

As rightly declared by the Singapore Parliament in February 2021, climate change is an existential crisis. Public housing is not, even though it is a hot-button issue (despite Singapore’s low birth rate, slow or zero population growth and high public housing occupancy rates). Have we been getting our priorities right in our long-term planning review?

For example, the Singapore Green Plan 2030 mentions about our ambition to be transformed “from mudflats to metropolis”. Yet I have come to realise something about the science of mangrove mudflats:

The very thing that we seemed to be ashamed of in the past is now helping us deal with the very crisis that we have brought upon ourselves because of our disrespect for and over-exploitation of Nature in the name of (unsustainable) economic development.

If we compare our post-independence narrative of the 57-year-old city-state with the natural history scientific narrative of our thousands-of-years old rainforest and mangrove forest heritage of a tropical island located at the Equator, I wonder how much we are actually force-fitting the concept of “eternal” economic growth and increasing population growth and density without further risking our climate, ecological and mental health thresholds.

Maybe we need to consider adapting the doughnut economic model for better sustainability and rethink the ambition to go “from mudflats to metropolis” because the mangrove mudflats (and forests) have been shown to help boost climate resilience, mitigate urban heat island effect and floods, and protect biodiversity and mental health of our population.

Mangroves can absorb up to five times more carbon dioxide by area than tropical upland forests due to strong carbon storage in the soil, but are being lost at an alarming rate. Both types of tropical forests play an important role in combating climate crisis and supporting biodiversity. (Illustration by IUCN)

Thus, conserving and restoring our forests, including Pang Sua woodland, is a scientifically proven, cost-effective, nature-based solution to deal with the danger of declining quality of life and deteriorating health and well-being for the populace (especially those who are most vulnerable to the impacts of climate change, such as the very young, the elderly, those with pre-existing health conditions, those who work outdoors and those who lack access to adequate air-cooling devices or facilities) in a metropolis that isn’t suited to a hot humid tropical climate in the first place. 

Summary of my proposal

I agree with the general recommendations on pages 71-72 of the EBS report, such as greening Pang Sua canal, establishing eco-links and planting trees intensively with shrubby undergrowth.

May I also propose the following scientific nature-based conservation and mitigation measures to further enhance the environment in Choa Chu Kang N1 study area, for the sake of better climate resilience, biodiversity support and public health protection in the long term?

(1) Avoid using chemical pesticides, including fumigation, in the vicinity, and instead leverage the help of natural predators of pest insects by ensuring the environment is conducive for frogs, toads, spiders, geckos, dragonflies, damselflies, etc to thrive (instead of concretising the ground surface and using harmful chemical sprays). As mentioned earlier, fogging is not very effective and tends to make dengue-carrying mosquitoes more resistant and harder to kill. It also harms benign insects and microorganisms, which are vital to a healthy functioning of the ecosystem. Even the use of Wolbachia-Aedes technology may have unknown or undesirable side effects such as the mutation of mosquitoes. Hence, we should use ecologically friendly mosquito control measures, such as making the environment habitable to mosquitoes’ natural predators, such as frogs, spiders and dragonflies, in Pang Sua woodland (as well as all residential areas in Singapore), in order to prevent dengue outbreaks successfully.

Spraying insecticides or pesticides in drains and gutters in the vicinity will contaminate the water that flows into Pang Sua canal, and then poison the fish and the predators that feed on them, such as herons, endangered smooth-coated otters, etc. This in turn may result in the accumulated poison being passed on to their future generations and possibly causing birth defects, neurotoxicity, greater susceptibility to diseases such as cancer, etc. (Photo by Jimmy Tan, which shows an excerpt of Bishan-Toa Payoh Town Council poster)

(2) Avoid or minimise the use of petrol-powered leaf blowers and lawn mowers, not only in Pang Sua woodland, but also in all housing estates, because they cause air and noise pollution (thus affecting people’s health and well-being), and harm microorganisms and invertebrates (which include pollinators, such as bees, wasps, moths, beetles and butterflies). For more than a decade, members of the public have been calling for these pollutive machines to be banned, as noted in my recent Youtube video about this issue. Otherwise, we are merely paying lip service to the importance of biodiversity when we cause harm to the various organisms (by mowing them down, compacting the soil, and destroying the weeds and wild flowers) instead of protecting them for giving us food security and maintaining a healthy functioning ecosystem.

(3) Observe holistically the United Nations’ Sustainable Development Goals, such as SDG12 “Responsible consumption and production”, by changing the way we produce and consume goods and resources, in order to reduce our ecological footprint, and SDG15 “Life on land”, by conserving and restoring the use of terrestrial ecosystems such as forests and wetlands, halting deforestation to mitigate the impact of climate change, and reducing the loss of natural habitats and biodiversity which are part of our natural heritage.

The UN Sustainable Development Goal 15 includes the goal to “promote the implementation of sustainable management of all types of forests, halt deforestation, restore degraded forests and substantially increase afforestation and reforestation globally“. This should apply to Singapore’s forests, regardless of whether we have a “forestry sector”, because the forests are considered renewable resources (in view of the economic value of their ecosystem services) and are part of the terrestrial ecosystems, which support biodiversity and provide ecosystem services to mitigate the impact of climate change. Otherwise, it would be inappropriate for us to claim that we are achieving sustainable development in this area. (Illustration by Margreet De Heer)

For example, if we do not practise responsible consumption and production, and even if we commit the grievous error of destroying Pang Sua woodland and all the other remaining forests in Singapore to build more BTO flats, there will still be a strong demand for public housing, since we have not addressed the insatiable human desire to keep wanting to consume more and more resources at the expense of the environment (and ultimately our quality of life and our very survival).

One of the reasons we keep losing our forests to the incessant building of new BTO flats is because of people wanting to buy BTO flats just to sell them immediately or shortly after meeting the five-year Minimum Occupation Period (MOP) to make quick profits.

Imagine the wildlife, such as pangolins, wild boars and palm civets, losing their forest habitats forever, while some humans occupy their former spaces just for a few years before moving or upgrading to another housing elsewhere.

The first scenario is largely a matter of life and death, while the second is largely a matter of lifestyle choice, comfort and convenience.

Ethically speaking, is it worth destroying forests (which are also natural habitats and wildlife corridors) just to cater to this kind of frivolous demand for public housing in greenfield sites (when we can choose instead to educate the public about environmental stewardship and sustainability and redirect such demand for housing towards renting flats/rooms, buying resale flats or new flats in previously developed lands, etc)?

Ecologically speaking, is it wise to replace forests with buildings and parks where newly planted trees take decades to grow, mature and provide the same level of ecosystem services as the existing large trees to combat climate emergency (in which we are racing against time “to avoid the worst ravages of climate breakdown“)?

Economically speaking, does it make sense to ignore the socioeconomic and health costs of losing forests while spending huge amounts of public funds to mitigate floods, dengue and zoonotic outbreaks, mental health crisis, etc?

“It has also been demonstrated that urbanicity could represent a possible risk factor for the spillover phenomenon, facilitating the virus transition from animals to humans via intermediate hosts. Particularly, deforestation policies may facilitate this process, resulting in the destruction of natural habitats of numerous species and reduction of biodiversity, as well as in greater interaction between wildlife and human activity.”

“The Influence of the Urban Environment on Mental Health during the COVID-19 Pandemic: Focus on Air Pollution and Migration—A Narrative Review”, 2021

Therefore, as Pang Sua woodland and canal are an integral part of the Green Rail Corridor, which provides “unique, highly accessible green spaces island-wide“, let us all keep in mind Minister Desmond Lee’s words:

“Community involvement and stewardship will be a key strategy in realising our vision for the Rail Corridor as a vibrant, inclusive, and shared community space. Our community spaces can only become more vibrant when they are designed, programmed and cherished in partnership with the people who treasure, care for and use them.”

“Speech by 2M Desmond Lee at the Launch of the Exhibition for Rail Corridor (Central)”, Oct 21, 2017

Indeed, it is only by treasuring and caring for our community spaces, such as Pang Sua woodland and Green Rail Corridor, will we be able to ensure that they become vibrant and inclusive, not only for ourselves but also the flora and fauna which co-exist with us.

In a nutshell, Pang Sua woodland provides food, shelter, fresh air, cool ambience and immune booster for wildlife and human visitors who travel along the Green Rail Corridor.

All are welcome to visit, regardless of race, language, religion, gender, social status or vaccination status.

No payment is needed.

The complimentary ecosystem services, which are of immeasurable value, are provided by Nature 24/7, 365 days a year.

(Photos of zebra dove, collared kingfishers, changeable lizard, monitor lizard and plantain squirrel taken by Jimmy Tan at Pang Sua woodland on 26 April 2022)

[Last updated 30 May 2022]

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3 thoughts on “My feedback to HDB on Environmental Baseline Study report regarding Choa Chu Kang N1 (including Pang Sua woodland and river canal)

  1. Pingback: My feedback to HDB on Environmental Impact Studies (EIS) report regarding Keppel Club Site – Nature and Us

  2. Pingback: My feedback on the EIS report regarding the proposed development at Tengah Forest North – Nature and Us

  3. Pingback: My feedback to Urban Redevelopment Authority (URA) on Springleaf Consultancy Study Environmental Impact Assessment (EIA) – Nature and Us

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