Cattle Ranching May Threaten Karst Ecosystems, Water Resources in Aru, Indonesia

karst lake
Mongabay Indonesia

Cattle Ranching May Threaten Karst Ecosystems, Water Resources in Aru, Indonesia

This story is the third installment of Mongabay Indonesia's series on cattle ranching in Aru. The second story can be found here.

Our reporting collaboration team, together with Forest Watch Indonesia researcher Aziz Fardhani Jaya, a member of the Indonesia Speleological Society, and Sammy Kamsy, a religious leader from Popjetur village, explored the karst landscape of Trangan, which at its highest point lies just 10 meters above sea level.

Sammy said that the plan for cattle ranching on Trangan was worrying, as it would potentially threaten the island’s freshwater resources.

Aziz explained that karst landscapes are found in limestone areas that are the result of sedimentation from shells formed around 15 to 23 million years ago.

Freshwater resources on Trangan Island, based on research from Forest Watch Indonesia and Lawalata IPB (2016) / Credit: Mongabay Indonesia.

Research conducted by FWI and Lawalata IPB in 2016 identified some 37 caves in the Aru Islands. “And that is not yet all of them because of the limited time for exploration and difficult access [to identify them],” Azis said.

The Kokoyar cave on Kobror Island, for example, has corridors with stalactites, stalagmites, soda straws, pillars, and flow stones which all have water dripping down from them.

Aziz said that many of the caves also have subterranean rivers.

In addition to important water resources, the cave rivers in the upper reaches of the Marfenfen River offer public transportation access / Credit: Forest Watch Indonesia.

In Trangan, the caves have long, bifurcated corridors but also few speleothems, such as stalactites and stalagmites.

“This difference is maybe due to the type of stone structure and the ecosystem above it,” said Azis.

Its water also follows an ebb and flow pattern meaning that this karst ecosystem is linked to the upstream areas of nearby rivers.

An aerial photograph of the Kongan Pond in Marfenfen / Credit: Forest Watch Indonesia.

“Karst is indeed a porous stone and acts like a sponge. It absorbs water. In here the water is salty or brackish, when it reaches the pond it already has become freshwater,” he said. 

Karst, he added, helps to safeguard the fresh water supply. Caves functions as natural drainage channels and the water that seeps from their walls also form subterranean rivers.

The Kongan Pond is used by bathers and as a source for fresh water / Credit: Forest Watch Indonesia.

Azis said that besides the karst landscape, forests and coastal mangroves were also very important in maintaining a supply of fresh water.

“A big issue in South Aru is the availability of water,” said Mufti Barri, Executive Director of Forest Watch Indonesia. 

Villages in Aru depend on on a number of fresh water sources, including springs, wells as well as rainwater. 

“But wells and springs are very dependent on the conditions of their environment,” said Mufti who is better known as Ode.

A study in, showed that livestock farming in karst ecosystems, such as on the Aru Islands, can lead to the pollution of karst aquifers by microbes.

A similar study conducted in the karst ecosystems southeast West Virginia, USA  showed that karst springs near livestock farms were intensively contaminated by fecal bacteria. 

“If animal feces from large-scale cattle ranching accumulate and get carried away by the water, they will also seep into the ground and increase the presence of E. coli bacteria and other [pathogens],” said Petrasa Wacana, a researcher who specializes in karst ecosystems.

The karst landscape, he added, is also home to the traditional populations of Aru. For remote island people, freshwater is vital resource for survival.

“If sources of clean or freshwater become damaged, they will suffer,” he said.

To read the rest of this story (in Bahasa Indonesia), please visit Mongabay Indonesia.

An abbreviated version of this story was produced with the support of the Earth Journalism Network and was originally published by Mongabay Indonesia on October 12, 2022. It has been edited for length and clarity.

The reporting was performed collaboratively by Mongabay Indonesia, Metro Maluku, and Forest Watch Indonesia. Reporters: Christ Belseran, Della Syahni and Indra Nugraha. Editor: Sapariah Saturi. Photo editor: Ridzki R Sigit.

Banner image: An aerial photograph of the Kongan Pond in Marfenfen / Credit: Forest Watch Indonesia.

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