#6: Climate Change in Cities - Sea Level Rise and Jakarta, the Sinking Megacity

Welcome to the Green Urbanist Podcast. My name is Ross and this podcast is about how urbanists of all kinds can step up the climate emergency.

This episode is Part 2 in a series on Climate Change is affecting and reshaping our cities. The topic is sea level rise and some of the points covered include:

• Why the sea level is rising more in some cities, and dropping in others.
• How melting ice caps shift Earth's rotation.
• The effect of melting glaciars on the oceanic circulation system, and what this could mean, and
• The story of Jakarta, the megacity that is being consumed by the rising tide.

Follow the podcast on social media
https://twitter.com/GreenUrbanPod
https://www.instagram.com/greenurbanistpod


Intro music by Tanoi
https://www.instagram.com/tanoiband
https://open.spotify.com/artist/5CO2UfOc9jkoImoS6Wmsx4?si=HmxCxRYkTreT7XCTW2G51g


Sources

Sea Level Rise

https://climate.nasa.gov/blog/3002/sea-level-101-part-two-all-sea-level-is-local/

https://tidesandcurrents.noaa.gov/sltrends/sltrends.html

https://e360.yale.edu/features/will_climate_change_jam_the_global_ocean_conveyor_belt

https://insideclimatenews.org/news/07052018/atlantic-ocean-circulation-slowing-climate-change-heat-temperature-rainfall-fish-why-you-should-care

Jakarta

https://jakartaglobe.id/context/jokowi-decides-jakartas-time-is-up-indonesias-new-capital-will-be-outside-java

https://www.eco-business.com/news/jakartas-sea-level-prompts-a-move-at-a-price/

https://www.wired.com/story/jakarta-is-sinking/

https://www.wired.co.uk/article/jakarta-sinking

https://www.nytimes.com/interactive/2017/12/21/world/asia/jakarta-sinking-climate.html

https://earth.org/data_visualization/sea-level-rise-by-the-end-of-the-century-alexandria-2/

https://www.bbc.co.uk/news/world-asia-44636934

https://www.

Thanks for listening!

Join the Green Urbanist Weekly newsletter: Substack

Support the Podcast by Donation

Contact Ross

Website
Linkedin
Twitter
Instagram

Transcript

Welcome to the Green Urbanist Podcast. My name is Ross and this podcast is about how urbanists of all kinds can step up the climate emergency.

This episode was originally meant to cover sea level rise, flooding and hurricanes as a kind of general water themed episode. But I ended up finding so much interesting and startling information just about sea level rise that I had to make the whole episode about it. This kind of thing happens to me a lot.

We're going to start by looking at the concept of sea level rise to just contextualise it and understand it a bit more in detail because I think we have heard so much about it over the years that we are almost a bit numb to it. Then I will go in depth looking at the story of Jakarta, the capital of Indonesia, which is the fastest sinking city in the world.

The predictions on sea level rise vary depending on how much carbon we emit and our developing understanding of the science. But before we start thinking about the future it is worth pointing out that sea levels are already rising and scientists have measured the yearly changes in level in many places around the world. So this isn't a problem for some distant future - we are in the midst of it. Of course, this is of interest to us as urbanists because many cities around the world are located by the sea like New York, Dublin, Barcelona and Manila, and other cities are directly affected by sea level rise, for instance the Thames River is tidal and so changes in sea level will effect London. In fact

Some predictions say that the mean sea level, meaning the global average, will rise by 2m by the end of this century - the year 2100. How do we contextualise this. Well, imagine your favourite beach. You probably know someone who is about 6 feet tall - 6 feet is just less than 2 metres, about 1.8 metres. So imagine them standing on the beach and the water is above their head. What does the landscape look like now? The whole beach has disappeared. If you're in a city or a town, maybe the water is now reaching the buildings on the shore and flooding their ground floors. It could be extending way into the city, filling streets with water. And that's not a flood event, that's just a normal day of 2 metres higher sea level.

What's interesting about sea level rise is that the mean sea level rise, of 2 metres, is a kind of average and actually results in a variation of local sea level. For instance as the Greenland ice sheet melts, the relative sea level around Greenland is actually expected to decrease. This seems totally counter intuitive. Surely if so much water is flowing out of the land, then the local effect would be especially high. But actually the weight of the ice sheet is so massive that it is acting to depress Greenland down. As the ice melts, the land is actually slowly rising up above the sea in a kind of rebound effect. A similar phenomenon is occurring to Sweden and Finland, whose land mass is still rebounding since the last ice age. However, the vast majority of coastlines around the world are currently experiencing rising local sea levels, and will continue to see this. The nations that are seeing the most significant local sea level rise are islands in the pacific ocean like Indonesia and the Philippines, and I will talk in depth about the capital of Indonesia, Jakarta, later in the episode.

There is a great interactive map on United States National Oceanic and Atmospheric Administration website, which I will share in podcast description, if you want to see in detail what the current trends are around the world. There are many reasons for this uneven distribution in rising sea levels. As I said, in some places the land is rising and in others, it is actually sinking, or subsiding.

Another factor is where the ice is melting. The NASA climate website has an article on sea level rise that says the following:
"As land ice in Greenland, Antarctica and elsewhere melts, it changes Earth’s gravity field and slightly shifts the direction of Earth’s rotation. This causes uneven changes in sea level across the globe. Each melting ice mass around the world creates its own unique pattern of sea level change in the global ocean. For example, when ice melts in Antarctica, the amount of sea level rise it generates in California and Florida is up to 52 percent greater in those locations than if the global ocean just filled up uniformly, like water in a bathtub."

But there is also the effect of the global oceanic circulation system - the pattern of the movement of water around the oceans. You may have heard that the reason northern Europe doesn't get as cold in the winter as Canada, despite being on a similar latitude, is because of the effect of the Gulf Stream, which carries warm water from the Gulf of Mexico northwards to Europe. Well, this is just one of many streams, drifts and currents that keep oceans in constant motion in a predictable pattern. However, the introduction of so much cold freshwater from the melting of ice due to greenhouse gas emissions is changing these currents, which could have ramifications on an epic scale.

In recent years there has been a growing body of evidence from academic studies that the North Atlantic current is slowing down. Its inconclusive as to whether this is a temporary fluctuation that will return to normal or a signal that the current will continue to slow down as a result of climate change and the introduction of cold freshwater from glaciers and ice sheets.

A 2016 article from Yale titled "How Climate Change Could Jam the World's Ocean Circulation" has this to say on the potential effects:
"If the North Atlantic current slows dramatically, then the entire Northern Hemisphere would cool; a complete collapse of the current could even reverse global warming for about 20 years. But the heat that ocean currents fail to transport northwards would make parts of the Southern Hemisphere even hotter. And a cooler north isn’t necessarily good news. Should the North Atlantic Current shut down, models show that changes in rainfall patterns would dry up Europe’s rivers, and North America’s entire Eastern Seaboard could see an additional 30 inches of sea level rise as the backed-up currents pile water up on East Coast shores."

We are still in the early days of this research so nothing is conclusive but it is just another example of how global climate is incredibly complex and even after decades of study, there is still much uncertainty about how our earth will change over the coming decades.

With that being said, I'd like to bring the podcast back to the present and the immediate future and look at a the story of how Jakarta in Indonesia is the fastest sinking city in the world.

Jakarta
Jakarta has a long history - There has been settlement here dating back at least to the 4th century. It was settled by Dutch colonialists in the 16th century and used as a port by the Dutch and British. Amazingly, it remained controlled by the Dutch for centuries, until after World War II, when Indonesia achieved independence. Since then the has country discovered oil and invested heavily in infrastructure, causing Jakarta to boom. As the capital of Indonesia, Jakarta city is home to 10 million inhabitants and its greater urban area has a population of 36 million. 

Jakarta now faces a dual problem. Sea levels are rising as a result of climate change and the city is actually sinking. I don't mean that in a metaphorical sense, I mean the actual ground the city is built on is subsiding. How could this happen? Well, many parts of the city do not have water piped in. They just don't have the infrastructure that we take for granted like kitchen taps with clean drinking water or showers. And the city's rivers are so polluted that residents can't source water from here. So they have to look underground. Underneath the city are naturally occurring aquifers of water that can be pumped up to the surface.

The way the government has dealt with the lack of water supply in the city is to say anyone who wants to pump for groundwater is allowed to. So all over the city, people extract whatever water they need from beneath the city itself. Because so much of the city is covered in impermeable surfaces like concrete, groundwater reserves don't get replenished quickly enough. This means that over time, as water is extracted it makes the soil unstable and it actually compresses downward, causing the city to sink. Some parts of North Jakarta, along the coast, have sunk by 2.5m in the last 10 years and continue to subside by up to 25cm a year.

The city has had more and more instances of flooding due to seasonal cyclones and overflowing rivers, and the tide has been gradually working its way inland. The response to this has been to build sea walls ad hoc on the coastline. These walls act as flood defences for a time but the tide is rising so fast that many walls are obsolete and are now sitting below the water level. It is clear that this strategy cannot work forever or in isolation.

In the last few years there have been many news articles with panicked headlines about Jakarta. A New York Times article in 2017 was titled "Jakarta is sinking so fast, it could end up underwater". Wired Magazine reported in 2019 with the title "The impossible fight to save Jakarta, the sinking megacity". These articles give the impression that the whole city is doomed. And even the government looks to be giving up. Last year, the president of Indonesia announced that the capital of the country will be relocated out of Jakarta. They have chosen a large plot of government owned land in Borneo and will build a new capital city in the vein of Brasilia or Washington DC. 

It is unclear however, what they really mean by "moving the capital". Of course moving the seat of government to a new location means all government staff and supporting workers and industries will move. But what happens to all the other residents? Are they left behind as the city sinks into the ocean?

At this point, it's worth backing up a little and understanding the geography of Jakarta. When news articles write something like "Jakarta will be under water in 20 years", its a bit disingenuous. It gives the impression that the entirety of the city will disappear and the whole population will be displaced. This is not correct. I said earlier that Jakarta is a city of 10 million people. That too is a kind of half truth. The population of Jakarta within its administrative boundary is 10 million. But the wider metropolitan area of Jakarta covers over 6'000 square kilometers and is home to 36 million people. It's the second most populous urban area in the world after Tokyo. For reference, Greater London, a very large urban area, I'm sure you'll agree, is about 1,500 square kilometers.
Next, consider the topography of Jakarta. The historic centre and port of the city is on the northern shore and sits at sea level, soon to be below sea level. This area is of course the most at risk and the area that is already experiencing the rise in sea level, causing streets and neighbourhoods to slowly disappear. But the land rise up to the south, towards the volcanic formations at the centre of the island. Because of the sprawling nature of the Jakarta metropolitan area, many people and businesses are located well above sea level and should be relatively safe. 

There's a helpful visualisation on the website Earth.org which I will link in the podcast description. It shows that by the year 2100, sea level rise and coastal flooding could displace 50% of the city's population - 5 million people. It doesn't define how much of the metropolitan area's population could be affected but looking at the graphic, it looks like it could be a similar percentage. 

So potentially half of the city may be underwater, including the port and parts of the central business hub. But much of the city will survive. Many people who can afford to will move to other cities, including the new capital. Both those who remain will reshape the city. Those who live in makeshift and informal settlements will move further and further out to the centre, densifying the suburbs and causing the megacity to sprawl even further. What happens when the central focus of the city, the downtown, disappears or is regularly flooded? Maybe the central focus of the city will change, moving inland with the population. This is urbanisation in the time of climate change.

But these models assume that the city does nothing to save itself. You may think that the Indonesian government is leaving Jakarta to its fate by moving to a new capital city and that the cheapest thing to do is to just let it flood. But the economics of this don't stack up. It's been calculated that abandoning North Jakarta, the community along the city's northern coast, would incur an economic cost of 200 billion US dollars. Even the most over-the-top, doomed to fail, megalomaniac plans for Jakarta's flood defence, which included excessive land reclamation and the creation of a giant bird-shaped property development in Jakarta Bay, would have cost only 40 billion dollars in comparison. So even from a cynical economists point of view, something has to be done. 

This is a multi-faceted problem that requires a complex response. Over the past 3 years, the city government has been restricting groundwater extraction to try to slow the sinking and groundwater reserves do seem to be replenishing slowly. However, the city's Chief Resilience Officer estimates that Jakarta needs to stop pumping up groundwater completely within 5 years. The city has many rivers that should offer a source of water but these are heavily polluted with industrial and domestic waste, just another of the city's many problems. This means that other sources of water like rainwater harvesting need to be explored, to provide people with an alternative to groundwater extraction. And these need to be provided on a huge scale very very quickly.
Then what about sea level rise? We're back to building walls. 

However, instead of building seawalls on land bit by bit, the Office of Public Works last year signed off on a 40km long off shore sea wall that will essentially close off Jakarta Bay. I haven't seen plans for this wall, I don't know exactly how it functions. But an article in Wired magazine described it like this: "The dyke will act as a huge breakwater to reduce the height of waves entering the bay, and to take the momentum out of storm surges so that they do not wash over the inner sea walls. Crucially, it leaves room for failure. The base level plan assumes that land subsidence will be addressed, but it includes contingencies in case it continues, or if sea level rise occurs faster than anticipated.". 

That same article includes an interview with a Dutch engineering consultant who has been working with the Jakarta government for years on the issue of flooding. There is a great quote from him at the end of the article. Speaking about trying to solve these big problems, he says: “I think you can compare it to the problem of climate change – where governments do see the problem, but they postpone very expensive and difficult measures towards the longer term and only focus on the quick wins… That is the nature of this kind of problem and the way politicians solve it,”. That is one of the lessons we are learning all over the world. We have known about climate change and the problems it would cause us for decades but we've been putting off the tough decisions and big investments until we are right on the edge of crisis, and sometimes even then we don't do what is necessary.

Finally, I'll leave you with a quote from a report published by the World Bank titled "Jakarta. Urban Challenges in a Changing Climate". They say:
"A few basic principles can guide the way forward for addressing climate change, disaster risk and urban poverty in Jakarta. First, climate change adaptation should be not so much an additional challenge to be layered onto existing policies and planning priorities, but rather an opportunity for the [city] government and key partners to gather their focus and priorities for the future. Given limited resources, the initial focus should be on addressing existing shortfalls in infrastructure investment and basic services, particularly
in drainage, piped water supply, housing, and transportation. Policies and investments should be based on improved information, including quantitative data and an understanding of community-level actions and adaptive capacities. Finally, enhanced collaboration – with the administrations of neighboring provinces, as well as with the local communities as active participants and partners – is crucial to the success of long-term action."

I think that seems like good advice for any city actually.

That's it for this episode. Thanks for listening. All the sources for this episode are in the podcast description. Keep an eye on my instagram and twitter account as I will be posting some visuals and articles to complement this episode. 

I see that many of my listeners are from the US and the UK so I would love to episodes focusing on flooding in the UK and maybe Hurricanes on the east coast of the Americas. Let me know what you would like to hear about on social media.