Unlike other megalopolises across the world, and in sharp contrast to the trend of global urbanisation, more people are actually leaving Jakarta than arriving. The city’s net migration rate has been negative since at least 1990.

Imagining a future for this chaotic metropolis is very difficult for most people who live and work here. If they imagine anything, it’s to detach their own future from the city.

Plan Bs are common; the fleeing started in the mid-1990s when famous artists like Agus Suwage moved out to cities such as Yogyakarta, with more attractive ecosystems and lower rents. Young, aspiring Indonesians continue to have faith in their capital as a source of income and social liberation – but not as a permanent home, or even a place to stake their long-term future.

Two of my younger friends (one 34, the other 36) are planning second lives in central Java where they have bought land and are designing houses. They’re not alone: South and central Jakarta have actually lost population – in part due to massive land-use changes – and the only thing preventing the entire city from shrinking is the birth rate. As it is, the population of Jakarta has more or less stabilised, at 9.6 million, with roughly 30 million in the greater urban area.

But the issue for Jakarta isn’t its 9.6 million residents – it is the 3.5 million commuters. Governing this city is no longer about managing places, but flows.

Facebook Twitter Pinterest Around 3.5 million Jakartans commute every day. Photograph: Beawiharta/Reuters

Traffic is the most visible problem, and you do not need to stay long in the city to experience it. Once limited to rush hour downtown, gridlock has now metastasised throughout the city: average motorised vehicular speed in 2014 was 11mph. Average spending on routine transportation, meanwhile, has risen to between 15% and 35% of income. In cities such as London and Singapore, it is between 5% and 8%.

What is not visible is even worse: the city is sinking at up to 20cm a year

Flooding, similarly, has become more frequent: from roughly every five years, to every rainy season, and now to almost every time it rains for more than three hours.

What is not visible is even worse: the city is sinking. Land subsidence is happening at a rate of 3cm per year in some parts of the city, 20cm in others. Not only is this causing more flooding, but it has the potential to damage the city’s drainage, piping and sewerage systems. The sea level in Jakarta Bay is rising 6mm every year.

Because only 50% of households have piped water – the lowest in Indonesia – residents rely on raw water supply, draining the natural aquifer beneath the city and causing the entire urban area to sink. Ironically, run-off is increasing, as deforestation upstream from the city and concretisation within are causing water to be wasted in alarming amounts. Jakarta now produces more wastewater than clean tap water.

Facebook Twitter Pinterest The population of Greater Jakarta has reached 30 million. Photograph: Mast Irham/EPA

What I hope for Jakarta’s future, therefore, is simple. I call it the “old agenda”. I would like for an average Jakarta working man or woman to spend no more than 10% of their salary on public transit. I would like piped water to reach at least 80% of households. And I would like land subsidence to stop: we must ban groundwater extraction, its main cause. In turn, this will greatly reduce flooding.

Others megacities have demonstrated that this is possible. Tokyo managed to stop land subsidence 40 years ago. Other cities, such as London, have cleaned their rivers not just of visual garbage but also invisible pollutants. Some have developed advanced public transport systems to free them from choking cars.

For Jakarta this will be difficult, but not impossible. Over the last two decades, research has produced enough knowledge for technical solutions. Bottom-up initiatives, too, are abundant, from zero waste efforts to communal sewerage processing. Schemes and designs to upgrade slums, rather than razing them, have been proposed. Other Indonesian cities have implemented many of these policies.

Facebook Twitter Pinterest Indonesia is the most populous country in south-east Asia. Photograph: Jefta Images/Barcroft Images

But forced evictions in Jakarta show that something is terribly wrong with our city’s governance. Understandably, we often put our hopes on the shoulders of politicians – but expecting politics to fundamentally change the status quo is delusional. Jakarta’s politics – and Indonesia’s – is entrenched in an elitist oligarchy, in which party bosses or their corporate backers are the main financiers. Political parties are in effect “owned” by them.

Some politicians have adapted their strategy to conform. There is a new strand of extra-budgetary populism: extracting funds directly from corporations or businessmen, by selling the city’s policies to build what pleases the people. This has resulted in a kind of politics that manipulates facts by reducing evidence-based urban science to subjective, anecdotal experience and a strain of anti-intellectualism that ignores the bigger picture.

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“My street is cleaner,” people say, ignoring the fact that the 6,000 tonnes of garbage collected is being moved unsustainably to other parts of the city. “My TransJakarta bus route is better,” people say, despite the fact that the total number of passengers is far below the target, let alone what is needed.

Perhaps it is better to put our hopes on bottom-up initiatives from individuals and communities. Thanks to communication technology and social media, independent initiatives can spread quickly around Jakarta. Take waste, for example: Adi Wibowo and his colleagues are spearheading zero-waste initiatives at a household level; Dewanto Bachrie’s Jakarta Osoji Club, Amaranila Lalita Drijono’s Bersih Nyok (Let’s Be Clean) group, and architect Martin Katoppo’s Design as Generator initiative are all volunteer efforts working to improve public space and reduce waste. On the canal bank near Jakarta Bay, Gugun Muhammad and his informal community have built several rafts dedicated to cleaning the canals themselves, in the hopes that they won’t be evicted by the city. These are just a few examples in my limited radar, and I am sure there are more.

I want to mention one other city in Indonesia: Pontianak. Here, citizens are taking the task of cleaning the city’s canal system into their own hands. And the local government has responded by collaborating with them. Pontianak is approximately 1/60th the size of greater Jakarta – but if the capital wants to hold on to its vision of being the great megacity of south-east Asia, it should start taking more notice of the smaller things in life.

Architect Marco Kusumawijaya is director of the Rujak Center for Urban Studies and former head of the Jakarta Arts Council

What would make Jakarta better, and what changes are most urgently needed? Share your ideas, thoughts, stories and pictures here. You can also contribute on Twitter and Instagram using the hashtag #GuardianJakarta