Researchers Suspect Hundreds of Mangroves in Tahura Died Due to Heavy Metal and Fuel Oil Pollution
A team of researchers from the Agriculture Faculty of Udayana University (Unud) revealed the results of their analysis on hundreds of mangrove trees west of the Bali Mandara Toll Road entrance in the Ngurah Rai Forest Park (Tahura), which have died and withered. It is suspected that the plants were contaminated with heavy metals and fuel oil.
The plants were found to have died simultaneously in early 2026. The death of the mangroves is evident from the change in leaf color, which initially turned green, then yellowed, then turned brown, and finally dried up and died.
The Unud plant health research team, which conducted the examination at the location, confirmed that the death of the mangroves was not caused by plant disease. However, the results found indicate environmental factors, namely suspected oil contamination in the area.
The findings are contained in a research report entitled “Analysis of Degradation and Crisis of the Mangrove Ecosystem in the Ngurah Rai Forest Park: Hydrocarbon Contamination in South Bali,” which was published on February 23, 2026. This study was compiled by a team of plant health researchers from Unud, coordinated by Dr. Dewa Gede Wiryangga Selangga.
“The death of mangroves that occurred in Tahura Ngurah Rai was not caused by plant disease attacks, but was triggered by environmental factors,” said Selangga, as quoted in his research report, Thursday (February 26, 2026).
He explained that the pattern of mangrove death is an important clue in diagnosing the cause. “Unlike the impact of sedimentation which occurs gradually, the death of these mangroves occurred simultaneously in certain vegetation blocks, leading to the suspicion of chemical contamination,” he added.
In the report, the research team highlighted the existence of several activities and major projects around the Tahura Ngurah Rai area. These include the Bali Mandara Toll Road, the Benoa Port reclamation managed by Pelindo, and the Pertamina energy distribution line that crosses the mangrove area.
“This area is in the middle of various development and infrastructure activities, so it is very vulnerable to pollution,” said Selangga.
According to him, mangrove death due to sedimentation or mud accumulation generally occurs gradually. However, the condition in Tahura Ngurah Rai shows a different pattern because it dies simultaneously in certain vegetation blocks.
“The death that occurs simultaneously in one block indicates a strong indication of pollution factors, not a natural process or disease,” said Selangga.
Suspected Oil Leakage
Based on field observations, the research team linked the death of mangroves to exposure to heavy metals and hydrocarbon compounds or oil. This suspicion was reinforced by the discovery of a fuel oil pipeline that crosses the mangrove area.
Coordination data records that there were repair and maintenance activities on the distribution pipeline from Benoa Port to the Pesanggaran Pertamina Depot in the period from September to November 2025. The report states that oil leakage is suspected to have entered the mangrove substrate and the cleaning process was not carried out thoroughly.
In response to this, Pertamina conducted a visual inspection on February 21, 2026, and stated that no oil layer was found on the water surface. Selangga emphasized that pollution is not always visible to the naked eye.
“In the mangrove ecosystem, oil is often trapped in the soil and covers the roots,” he said.
Selangga explained that oil that enters the pores of the sediment is toxic and can interfere with plant nutrient absorption. The impact is not immediate, but can cause mangroves to die within a few weeks of exposure.
In addition, the presence of the toll road makes the flow of water in the mangrove area slower. As a result, pollutants are not carried away by the current, but instead settle and accumulate around the mangrove roots.
In addition to the suspected oil leakage, the research team also highlighted the possibility of small leaks or pipes that have rusted underground, making them difficult to detect.
Based on the results of the research, the team concluded that the main cause of the death of hundreds of mangroves in South Bali is pollution from heavy metals and fuel oil.
“The most obvious characteristic is that the death does not spread randomly, but is concentrated in certain vegetation blocks,” concluded Selangga.
Previously reported, member of Commission III of the Indonesian House of Representatives, I Nyoman Parta, revealed the condition of damaged and dead mangrove plants, allegedly due to a fuel oil pipeline leak in the area.
Parta requested an explanation from the parties concerned regarding the condition, including Pelindo and Jasa Marga. According to him, in November 2025, there was pipeline maintenance activity in the distribution line from Benoa Port to the Pesanggaran Pertamina Depot, Denpasar.
“I suspect this is not a natural death, it needs to be proven. However, initial information indicates that there is a suspected leak in Pertamina’s fuel oil pipeline or another company operating in this area,” said Parta.
Meanwhile, Area Manager Communication, Relations & CSR Jatimbalinus Pertamina Patra Niaga, Ahad Rahedi, stated that Pertamina will conduct further investigation into operational activities in the past few months. Based on the results of visual inspections in the field, he said, no oil layer or strong smell of fuel oil was found around the location of the dead mangroves.
“Pertamina Patra Niaga through the Sanggaran Fuel Terminal will carry out an examination of the chronology of operational activities in the past few months, especially related to pipelining work around the Benoa area,” said Ahad Rahedi, Saturday (February 21, 2026).
Pertamina, he said, promised to accelerate the restoration of the mangrove area. Ahad said Pertamina will work with other related companies that have operations in the Benoa area, in accordance with the direction of the DKLH (Department of Environment) of the Province of Bali.