The company, PT Poso Energy, plans to dredge the Poso River, scraping tons of soil from the riverbed and dumping it in a marshy area downstream to strengthen the current where the river will flow over the turbines.

If completed, the dredging threatens sustainable fishing practices, disrupting the livelihoods of thousands and an economy that supports far more. Conservationists also fear re-engineering the lake will disrupt an ecosystem with uncounted endemic species, one so ancient it can be used to study evolution.

“Is it not cruel that we have to protect our own culture on our own land?” asks Protestant pastor Yombu Wuri, 63, who joined a group of activists after he saw other churches pressure pastors to avoid protest.

Wuri, Bontinge and other opponents of the project call the group the Alliance of Lake Poso Guardians, and in November 2019, they lodged a police complaint alleging PT Poso Energy is damaging the environment in an area the local government promised to protect.

The alliance is a small group of outspoken farmers, fishers, and other concerned locals. For almost a year, they have protested PT Poso Energy, owned by the family of former vice president Jusuf Kalla, with online campaigns and in meetings with local officials and police to explain the cultural significance of the lake. Early last November, after the company dismantled an almost century-old bridge, five more groups joined from the provincial capital, Palu.

Because the company already has an environmental permit for the project, local police have placed the burden of proof on the anti-dam alliance. If the activists wish to pursue legal action, the police say they will first need to furnish scientific evidence the company is damaging ecosystems.

The alliance has found an ally in a government authority, the Indonesian Institute of Sciences (LIPI). But with low funds, the team led by Gadis Sri Haryani, LIPI’s head of limnology, has begun to pursue other means of funding. Due to time constraints, they may only find funding when the project is close to completion.

“People have called us anti-development and anti-modernization, but why do you have to damage an ecosystem just to create electricity?” says Wilianita Selviana, 34, a former activist who has watched the dredging begin from her riverside house.

Indonesia has set itself an ambitious goal of obtaining 23% of its energy from renewable sources by 2025 and 31% by 2050. Despite a growing body of research suggesting that large hydroelectric dams can be a significant source of carbon emissions, the government remains resolutely committed to hydropower. It aims to generate 11% of total electricity from hydropower, up from 6.9% in 2018.

Large hydropower plants are necessary, a minister wrote in an International Hydropower Association report, to meet the demand of hotspots like North Konawe in Sulawesi, where nickel mines and smelters require hefty amounts of electricity. PT Poso Energy has said its plant’s electricity will fulfill local needs, but power will also be channeled to nickel hotspots via the island’s grid.

“It’s not possible that the electricity just goes to us here, because we don’t need that much. The electricity will likely go to Sorowako, for example,” says Lian Gogali, head of the local activist group Institute Mosintuwu, referring to one of the oldest sites of nickel mining in Indonesia, where transmission lines connect to Poso. Indonesia’s state power company plans to build 200 kilometers (120 miles) of transmission lines from the Poso plant to Morowali, another center of the nickel industry.

Meanwhile, Lake Poso, and the communities who depend on it, will be left transformed.

In reshaping the river, PT Poso Energy will strengthen the current to the hydropower plant, but drastically change Tentena village, located where the lake narrows out into a river.

The roughly 2 million cubic meters (71 million cubic feet) of soil that will be dredged from the riverbed will be relocated to a bend in the river that locals call Kompo Dongi, creating an artificial landmass that PT Poso Energy says will harbor a park for tourism and conservation.

In this small, marshy area, Poso natives hold a communal fishing event called mosango. When the dry season brings water levels down, hundreds of people from villages around the lake gather in the waist-deep water, wait for fish to gather, then simultaneously place upside-down bamboo baskets in the water, each trapping a small portion of the fish.

“It’s an icon of Poso, because it requires that we all work together and share the rewards,” says Hajay Ancura, 54, a local farmer.

Dredging boats arrived last year and started pumping soil into the marsh. This year is the first in hundreds that mosango will not be done, according to locals. In October, two women were arrested after boarding a dredging boat with gasoline and threatening to set it alight.

As PT Poso Energy fills in the dirt to create the landmass, it’s dredging soil from the area where two enduring eel fisheries feed the local economy.

Yusuf Manarang, 44, catches eels at the river’s mouth using a method locals call monyilo. When seasonal waters rise and the eels embark on a nighttime migration between the lake and sea, he boards his small boat with a spotlight and 4-meter (13-foot) spear. He can earn $100 from a night’s fishing, selling the eels to companies that export them as far as Japan. It has given him enough money to put his four kids through school.

“The government asks us, why aren’t you rich yet?” Yusuf says. “If the goal is to help us prosper, then build facilities that help us prosper, like schools, higher education, and hospitals. How is it possible that business is prioritized?”

Another fishing technique, called wayamasapi, is conducted from boathouses, from which fences stretch like wings across the river. The technique relies on the seasonal water rise to funnel eels through the V-shaped fences to a raised cage that traps them alive.

The traditional barrier between the areas for the monyilo and wayamasapi fisheries was the wooden Pamona bridge, first built almost a century ago, and renovated in the 1960s. For locals, the bridge was both a sign that native Indonesians could accomplish a technological marvel without the help of the Dutch colonial government and a popular photo backdrop.

Last month, PT Poso Energy dismantled the bridge because it was too low for the ships beginning to re-engineer the river.

“It’s as if our identity disappeared,” says Bontinge, who with Wuri led group prayer sessions next to the bridge as it was being dismantled.

PT Poso Energy maintains the bridge will be rebuilt, and will be more stable, to appeal to tourists, but a spokesperson did not respond to questions.

“The tourists that have come here over the years don’t come to see new things, they come to see the cultural gems that have endured generations,” Yusuf says. Like many fishers afraid of publicly protesting the project, he hasn’t joined the alliance, even as he believes deepening the river will make his profession impossible.

Humans are a relatively recent addition to the lake environment. The hydropower dam will make a reservoir from an ecosystem so old and so isolated that it’s like an experiment in evolution.

Lake Poso was formed roughly 2 million years ago, when tectonic plate shifts left a cavern 500 m (1,640 ft) deep in the heart of Sulawesi. Rains came, and they brought life. Isolated from other lakes and waterways, the lake evolved dozens of unique species that are found nowhere else on the planet.

Researchers designate Lake Poso an ancient lake, meaning it has lived through at least one glacial cycle, roughly 130,000 years. Such lakes offer scientists a natural laboratory for biodiversity, evolution and geological history, but as hotspots for endemism, they are potentially more vulnerable to ecological changes.

The lake is a global “gem,” says Doug Haffner, an emeritus professor of limnology who has been sampling Lake Poso for a quarter century.

Unique ricefish and several other fish found only here have been listed as endangered or critically endangered. A goby with a dragon-like dorsal fin may already be extinct. Much of the lake’s high endemism is present among mollusks and shrimps. Of the four eel species that migrate 50 km (30 mi) between ocean and lake, one is endemic to Sulawesi.

In general, though, knowledge about the species of Lake Poso is scarce, says Haffner, also the founding director of the Great Lakes Institute for Environmental Research.

“I think the big issue with Poso is the almost complete lack of information,” he says. “No one has really worked on Lake Poso, I think we are the only group with information on lake physics, chemistry, and biology, and that is a very limited data set for one of the most important lakes in Indonesia.

“There are not that many ancient systems around, and we recognize them as real harbors of biodiversity.”

When the project is finished, electricity demand will determine when the river flows rapidly or slowly, and the lake level will rise or fall accordingly. The lake’s waters don’t mix from top to bottom, but adjusting the lake’s level may disturb the natural balance and spread eutrophication, depleting dissolved oxygen levels. Kompo Dongi, the marsh being filled in, is also where many endemic fish find safe breeding grounds.

The eels that support wayamasapi and monyilo need to be able to migrate along the river, says Fadly Tantu, a fisheries lecturer at Tadulako University in Palu.

“The eels are like salmon, traveling between the salt and fresh water, but many researchers believe they’ll be trapped by the dams, because nobody has assessed whether the fishways PT Poso Energy built are adequate,” he says by phone from Palu.

Gadis Sri Haryani, the head of limnology at LIPI, says she has seen company video of adolescent eels making the trek upstream, but no adults going downstream. Although many hydropower companies rely on them to obtain environmental permits, researchers say fishways are not a proven technology.

Fewer than a quarter of eels in a European river, for example, were able to pass a dam in their migration pathway. And researchers found in Southeast Asia that fishways designed for individual species may ignore the broader impacts on riverine life.

“We need electricity, but on the other hand, the environment needs to be protected so that the migrations aren’t disturbed, because the eels are the local economy,” Gadis says.

In December, Gadis organized a focus group discussion with PT Poso Energy, local government officials, and opponents of the project. It was the first time they had all sat in a room together, she says.

For the project’s opponents, promises of economic development have swirled for more than a decade. Ceding even more ground feels like stepping backward so a modernistic vision can push forward without them.

“Our guests have a lot of desires,” says Wuri, the pastor, referring to PT Poso Energy. “Then they also ask for another space, the center of our culture. Are we supposed to exit our own house and build a whole other area behind our own land?”

Speaking during a service at his local church in Tentena, Wuri urged his congregants to consider the impact of the dam on future generations: “What will our grandchildren think of us? Friendly? Or stupid?”

Banner image: Yombu Wuri (in sunglasses) speaks with a resident of one of the communities along Lake Poso, by Ian Morse for Mongabay.

Follow Ian Morse on Twitter: @ianjmorse

FEEDBACK: Use this form to send a message to the author of this post. If you want to post a public comment, you can do that at the bottom of the page.