Infrastructure & Development / Southeast Asia

The Cross Island Line: Timeline, Controversy, and Impacts

by Gwyneth Cheng
Length 6 min

In December 2019, the Singapore government announced that the Cross Island Line will cut through the Central Catchment Nature Reserve, with construction to begin this year. What are the consequences of this decision for us and our environment?

Singapore is a nation with ambitions.

It’s home to the first River Safari in Asia, the world’s tallest indoor waterfall, and the largest dome structure on Earth. Nothing seems impossible for the small city-state.

Yet Singapore is dreaming bigger. While most of the country’s ambitions take the shape of unique architecture and towering structures that dominate its skyline, its latest project is much more subtle.

So subtle, in fact, that it will be buried underground.

Aptly named the Cross Island Line (CRL), the city-state’s latest venture is a Mass Rapid Transit (MRT) line that will have trains zipping back and forth between eastern and western Singapore, its reach stretching from the least popular residential areas to the most ulu work locations.

Announced in January 2013, the nation’s eighth MRT line aims to ease the process of supporting a growing average of 7.5 million commuters a day, while decreasing overall travel time by up to 40 minutes.

As it is, the CRL is probably our most ambitious transportation project to date.

In theory, it seems like the perfect plan. The addition of this MRT line will prompt more people to take public transport. Singaporeans will also enjoy higher rates of productivity without compromising the time they spend outside of work.

Reality, however, paints a different picture. Since its conception, the CRL has been hindered by waves of controversy, primarily because the MRT line has to intersect the Central Catchment Nature Reserve (CCNR) for it to cross the island.

What’s the big deal about the CCNR?

The Central Catchment Nature Reserve is Singapore’s largest nature reserve. More important, it contains patches of Singapore’s remaining 0.2% of primary forest from 150 years ago.


Singapore maps in 1945 and 2020. In both maps, green patches represent vegetation cover. Most of the forests left in Singapore are secondary forests, which are regrowth or replanted forests.

Sources: Wikimedia Commons, Google Earth

This might not mean much to the average urbanite, but the truth is quite the contrary. In Singapore, our forests act as lungs too, and primary forests are particularly effective ones, since they absorb more carbon than regrowth or replanted forests. In other words, they are more effective at preventing the rapid heating of our island and clearing our air of pollutants.

Primary forests can also support more wildlife, providing unique habitats that regrowth or replanted vegetation cannot fully replicate. These lifeforms are highly sensitive to change, and altering their habitats in the smallest ways risks destroying large swaths of their population.

What this means is that once we lose our primary forests, they are gone forever. While the Singapore government has been ramping up efforts to plant more green around the country, these new patches of vegetation will not support us and our wildlife the same way our primary forests can.

No one has expressed this opinion louder than local environmental groups. In 2013, Nature Society (Singapore), the nation’s most prominent environmental non-profit organisation, proposed an alternative route for the CRL that would go around the CCNR instead of through it.

Aligning interests: What are the benefits and costs of each option?

With a second alignment option in contention, the Land Transport Authority (LTA) performed in-depth analyses of both routes to compare and decide which would be more suitable for the CRL.

Here is what they found:

The Cross Island Line: Timeline, Controversy, and Impacts

The difference in distance, travel time, and project cost between both alignments. Source: Channel News Asia

Significance of impacts caused by alignment option 1 and option 2, ranging from negligible to critical. LTA concluded that all of the impacts caused by the construction and operation of the CRL will be ‘negative’.

Source: Land Transport Authority

The impact assessment chart above is slightly conservative, as it assumes that these are the potential impacts when all mitigation measures are employed thoroughly and that ‘unplanned’ events, such as accidental spillage of harmful liquids, fires, etc., will not occur.

What’s the verdict?

For certain, the CRL will reap economic benefits for Singapore by making its people more efficient and productive. While the CRL’s social impacts tend to be negative, many of them are short-term and depend on how far people live from the alignment sites.

The brunt of the impact still falls on the environment, especially for alignment option 1, even if we assume that mitigation measures are thoroughly employed. Unplanned events during construction, which are not visualised above, can cause further damage to the environment.

We should remember that many of these environmental impacts are often death sentences: permanent and irreparable the moment the damage is done.

Regardless, construction is slated to begin this year, although not everyone has given up. Environmental influencers are calling for greater awareness of the issue. Nature groups have urged the government for further action before construction begins. Recently, Member of Parliament Louis Ng’s post on Facebook regarding the CRL’s impacts gained a fresh round of attention.

It remains to be seen if these responses will work, but what we do know is that despite the government’s best efforts, many are not yet appeased.

Are you?

The EIA details the impacts caused by each worksite that will be built along each alignment option. To analyse the impact caused by the whole alignment, the author took the largest possible impact significance across all the worksites along the alignment and listed that as the overall impact significance of that alignment. For example, at alignment option 1, if the impact significance on surface water quality at worksite 1 is ‘major’ and that of worksite 2 is ‘moderate’, the overall impact significance of alignment option 1 on surface water quality will be ‘generally major’. This is to ensure that the worst possible impact that each alignment could cause is stated; many of these impacts are irreversible, and downplaying them will not lead to a full picture of how much potential degradation the alignment could result in.


  • central catchment nature reserve,
  • controversy,
  • crl,
  • cross island line,
  • explainer,
  • impact,
  • timeline

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