Curb urban sprawl, conserve forest watershed to benefit flood-prone Jakarta

The Ciliwung River seen from the city of Bogor on the outskirts of Jakarta. LN/Julie Mollins
Grace Susetyo
21 March 2018
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JAKARTA (Landscape News) – Keeping cities compact by curbing urban sprawl and maintaining intercity government collaboration for the preservation of upstream forests is crucial for making cities sustainable, said Marco Kusumawijaya, director of the Rujak Centre for Urban Studies.

Supporting a population of 10 million inhabitants and 2.5 million daily commuters from neighboring municipalities, Jakarta is situated along the swampy Ciliwung-Cisadane drainage basins. The city is sinking 3 to 18 centimeters per year from the weight of construction and groundwater depletion. Towards the north coast abutting the Java Sea, 40 percent of Jakarta lies below sea level, and poor drainage leaves the rest of the megalopolis prone to flooding in the rainy season.

As of 2017, green spaces make up just under 10 percent of Jakarta’s land area—one-third of Indonesia’s legal requirement for urban parklands to cover 30 percent of a city’s total land area.

According to landscape consultant Nirwono Joga, meeting this requirement by 2030 will entail converting 0.5 percent of Jakarta’s land area (650 hectares) into green spaces each year – a difficult target to meet, considering Jakarta’s own population pressures as well as those from surrounding cities.

As a proponent for compact cities, Kusumawijaya expressed skepticism for expanding urban parklands. A more effective roadmap towards maximizing Jakarta’s ecological performance is to protect the upstream forests of Ciliwung-Cisadane watershed, Kusumawijaya told Landscapes News ahead of the U.N. International Day of Forests, which this year focuses on forests and sustainable cities.

“Urban parklands must not be established at the expense of a city’s compactness, or the living conditions of the urban poor,” said Kusumawijaya. “Parklands should be preserved in consideration of the watershed of which the city is part. What matters more than expanding Jakarta’s parklands is protecting the forests upstream of our watershed.”

At issue, is that only 13 percent of the Ciliwung watershed is currently covered by dense forests, and residential areas along the watershed continue to increase exponentially, Pikiran Rakyat newspaper reports.

About 5,700 hectares of upstream forest were lost along the headwaters of the Ciliwung watershed between 2000 and 2016, according to Forest Watch Indonesia. Around 50 percent of protected forests upstream of Ciliwung have been converted into residences, tourist accommodation, and agricultural plantations, making access to clean water difficult for poor people, FWI reports.

MITIGATING HEAT ISLANDS

Without sufficient green spaces and trees, the U.N. says that cities become “heat islands,” leading to worsening air pollution, soil quality and related public health problems. Strongly integrated land-use and sustainable urban development strategies to protect forests and trees are required to ensure safe supplies of food, water and energy.

Kusumawijaya sees urban sprawl sprawl—the horizontal development of low-density, car-dependent human populations to single-use lands—as a major threat to the upstream forests of the watershed of which Jakarta is part.

Limited vertical development is a way to counter urban sprawl, but the optimal number of floors causing minimum negative impact to a given plot of land is difficult to determine. Based on Kusumawijaya’s studies of floor area ratio and historical land use in several Asian and European cities, he suggested this optimal number ranges from between six to eight floors.

“After a certain number of floors, higher buildings do not mean saving land for more efficient cities.,” said Kusumawijaya, explaining that concentrations of higher buildings generate heat islands, and require larger swathes of vacant parklands to mitigate.

“But (having large swathes of parklands in between high rise developments) is inefficient as it lengthens the distance between one place with human presence and another, which means spending more energy and money on transportation. Services become expensive, longer water pipes are needed, and it doesn’t do the city’s social landscapes any favors either,” said Kusumawijaya, clarifying why low-rise vertical development spaced out with compact parklands is a better alternative.

INTEGRATED STRATEGIES

One expert, geographer Melissa Keeley, writes in the Journal of Environmental Planning and Management: “While urban density intensifies the environmental impact of development locally, it decreases environmental impact within the larger region.”

This means that a more compact Jakarta may entail continued overcrowding and human pollution, instead of spacing out its development with  vast green parklands. However, keeping human activities concentrated in metropolitan Jakarta and preventing the city from sprawling into the upstream forests of the nearby cities of Bogor and Depok is an effective way to keep the total environmental impact affecting the entire Ciliwung-Cisadane watersheds in check.

With 50 percent of the world’s population living within a 3-kilometer radius of a surface freshwater body, and 10 percent living further than 10 kilometres away, according to a 2011 report, most cities are part of a watershed. Hence integrated forest conservation strategies involving all municipalities covered by a given watershed becomes crucial, said Kusumawijaya.

“A (downstream) city’s flooding problems cannot be solved without collaborating with related municipalities along the watershed to conserve its upstream forests. The more deforested the lands along the headwaters are, the faster floodwaters flash downstream,” he said.

Additionally, the conservation of upstream forests ensures a relatively stable water supply for downstream cities, in terms of quantity as well as quality. “Deforestation can cause floods in the rainy season and droughts in the dry season,” said Kusumawijaya. “We consume groundwater faster than we can put water back in the ground, so upstream forests play an important role in retaining groundwater.”

Kusumawijaya added that there is no one-size-fits-all strategy for the integrated conservation of forests along a watershed, as every city is geographically unique.

Municipalities upstream on the Ciliwung such as Bogor, should refrain from the dense metropolitan development as seen in Jakarta, he added.

Instead, Jakarta and Bogor could collaborate by taking on different environmental and economic roles that complement each other’s needs as sister cities along the same watershed.

The development of recreational villas continue to encroach on Bogor’s forests, mostly to satisfy the appetite of Jakarta residents for convenient tourism. Additionally, rising demands for agricultural commodities also means more deforestation and pollution from chemical runoffs in the hinterlands.

“If you know the limits, tourism and agriculture can coexist with upstream forest conservation. Natural landscapes are not just there for the view, but also to perform ecosystem services for our benefits. But to know the limits, one must know how to calculate environmental impact,” said Kusumawijaya.

ECOLOGICAL PERFORMANCE

While upstream forests are cleared to cater for the interests of urban consumers who mostly live downstream, urban parklands make an attractive subject for policymaking, dressed up as a city’s initiative to mitigate climate change.

“The ecological function of urban parklands in combatting carbon emissions is insignificant,” said Kusumawijaya. However, cities can do their part in “going green” by implementing strategic policies that maximize the ecological performance of a given area rather than simply expanding the land area of urban parklands.

“A 10-square meter plot could be turned into a pebble garden, or could be grown with a banyan tree. Same size (piece) of land, very different ecological performance,” he said. A banyan tree could produce oxygen, regulate heat, and support water absorption to help replenish groundwater supplies, in contrast to a pebble garden that might only serve aesthetic functions.

Affirming that it does take a certain size of land area to generate significant ecological benefits, Kusumawijaya added that cities need more data driven studies to determine how to maximize the ecological performance of potential parklands while keeping the city compact.

RELATED

The Green Area Ratio: an urban site sustainability metric

Without Forests, Jakarta’s Water Situation Worsens

Declaring Independence for the Lands and Waters of Puncak, Bogor

Puncak Landslides and Disasters Caused by Changes in Land Use


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