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Relocating mangroves for Indonesian highway ‘not that easy,’ expert warns

  • Indonesia is building a toll road and levee along the north coast of Java Island in an effort to reduce congestion and prevent tidal flooding.
  • But the project will cut through swaths of mangrove forest, some of which will be relocated, according to officials.
  • An environmental expert has warned against the mangrove relocation plan, noting that poor procedures will likely lead to failed growth of trees at the new sites.

PURWOKERTO, Indonesia — An environmental expert in Indonesia has warned against a government plan to relocate mangrove trees along the north coast of the island of Java to make way for a highway and levee project.

The project, billed at $557 million, will run 27 kilometers (17 miles) from Semarang, the capital of Central Java province, east to the district of Demak, and is touted as a solution to coastal flooding in communities along the strip. The project’s concession covers almost 540 hectares (1,330 acres) of land, some of which includes swaths of intact mangrove forest.

The Central Java environmental agency says it will relocate mangrove trees from three different sites in the project area, spanning a total of 46 hectares (114 acres), as part of efforts to offset the environmental impacts of the highway project. It has not yet determined the new planting site, however.

The Java transportation network map, with roads in yellow. Image by Gunawan Kartapranata via Wikimedia Commons (CC BY-SA 3.0).

“You can’t just relocate them and expect the mangroves will just continue to grow. That’s not how it works,” Rudhi Pribadi, a marine researcher at Diponegoro University in Semarang, told Mongabay Indonesia in a recent interview.

Rudhi said that mangroves required particular ecosystem criteria, such as water salinity, to stay alive. He added that a comprehensive study on potential relocation sites would have to be done before any relocation took place.

“And it’s not easy to meet those criteria,” he said.

Rudhi said much of the mangrove ecosystem along the north coast of Java has been damaged for the development of other infrastructure projects, while the rehabilitation efforts associated with those projects have failed to grow new trees due to poor procedures.

He added that efforts must also be made to mitigate coastal erosion and land subsidence, which will intensify with the loss of mangrove cover.

Widi Hartanto, the acting head at the provincial environmental agency, said his office was monitoring the development of the highway project to ensure minimal impact on the environment, particularly the mangrove ecosystem.

“Obviously, we visit the sites to know the reality. If there’s something that’s lacking, we will give advice accordingly,” Widi said.

The construction of the new Semarang-Demak highway along the north coast of Indonesia’s Java Island. Image courtesy of the Indonesian Ministry of Public Works and Housing.

Work has started on the toll road project, which is included in a slate of nationally strategic infrastructure programs. The road will include a 10-km (6-mi) stretch atop a levee on reclaimed land. The levee is expected to prevent tidal flooding in the area, where decades of development and groundwater extraction have caused the land to sink, in some places below sea level, affecting more than 6,800 hectares (16,800 acres) of land. Java’s north coast, including the capital, Jakarta, is dealing with severe land subsidence problems.

The new project could exacerbate this problem rather than resolve it, according to the findings from an interdisciplinary study carried out between August 2019 and February 2020. The researchers behind that study say the land reclamation required to build the levee will alter coastal currents in the area, impacting local fishermen. They also cite what they call key omissions from the project developer’s environmental impact assessment, such as a comprehensive public consultation and details about where the construction material for the road and levee will be quarried from. The biggest beneficiaries, the new study says, will be the industrial estates in the region.

The government awarded the contract in September last year to a consortium that includes state-owned construction companies PT Pembangunan Perumahan and PT Wijaya Karya, and private developer PT Misi Mulia Metrical.

The researchers say the project appears to have been designed ultimately to connect the Kendal Industrial Zone and Jateng Industrial Park Sayung with the capital Semarang, home to the province’s main port.

The Kendal Industrial Zone, west of Semarang, is the province’s biggest development project, spanning 2,200 hectares (5,400 acres) and owned by Jakarta-listed developer PT Jababeka and Singapore-listed Sembcrop Development. Jateng Industrial Park Sayung, in Demak, is much smaller, at 300 hectares (740 acres), and is operated by PT Jawa Tengah Lahan Andalan, a subsidiary of property conglomerate Mugan Group.

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Another potential beneficiary of the project is an industrial park and housing estate planned for construction near the Semarang section of the highway. The developer of that site is PT Pembangunan Perumahan, one of the co-developers of the Semarang-Demak highway.

These industrial estates will eventually have quick access to Semarang’s Tanjung Emas Port via a planned toll road linking directly to the Semarang-Demak highway. Indonesia’s public works minister announced the Semarang Harbour Toll project in April this year. Construction is expected to begin next year and end in 2023, at a total cost of 22 trillion rupiah ($1.5 billion) for the 21-km (13-mi) toll road.

“The mangroves in Semarang have been destroyed by the development of a port in Kendal. Meanwhile, the mangroves in Demak have been damaged by the development of Tanjung Mas Port in Semarang,” said Rudhi, who isn’t involved in the study.

“Any changes to the environment will have their impacts,” he added.

A highway in Central Java. Image courtesy of Ya, saya inBaliTimur via Flickr (CC BY-SA 2.0).

This story was first reported by Mongabay’s Indonesia team and published here on our Indonesian site on April 16, 2021.

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