A WWF-led expedition in Southeast Sulawesi found severely reduced hard-coral cover in nine out of 38 sampling sites.
Researchers point to sediment created by the province’s nickel mining industry as one of the primary drivers of reef destruction.
An outbreak of coral-eating crown-of-thorns starfish is also contributing to the problem.
Southeast Sulawesi Province consists mostly of water. Around 75 percent of the province’s territory lies offshore, in the Banda Sea and the Gulf of Boni. Its coasts and waters are home to a tremendous variety of flora and fauna, including 20 species of mangroves, 93 species of ornamental fish and endangered species like the hawksbill and loggerhead sea turtles. These fisheries are also vital for the province’s economy, producing an annual catch of up to 542,000 tons of fish per year.
Now, the region is threatened by environmental damage due to a growing nickel mining industry and its associated infrastructure, as well an outbreak of a voracious coral-eating starfish.
A recent expedition found that nearly a quarter of Southeast Sulawesi’s reef ecosystem is badly damaged. The expedition, referred to as XPDCSULTRA, was a joint effort by WWF-Indonesia, international non-profit Reef Check foundation, Southeast Sulawesi’s Agency for Fisheries and Marine Affairs (DKP), and Halu Uleo University. The team observed the province’s coastal ecosystem and collected data on coral reef conditions by diving into 38 sampling sites in Lasolo Bay Marine Park, the Southeast Sulawesi Marine Protected Area and the non-protected waters around Wawonii Island.
Across the province, researchers found that hard-coral cover is low, while rubble and high levels of sedimentation are common. They also found an outbreak of coral-eating crown-of-thorns starfish (Acanthaster planci), which exacerbate the declining quality of the coral reef ecosystem.
Estradivari, marine science coordinator for WWF-Indonesia and the lead scientist of the expedition, told Mongabay she suspects nickel mining in the region is the primary culprit of the damaged ecosystem, though further study needs to be done.
Indonesia has the world’s most abundant supply of nickel and Southeast Sulawesi holds some of the country’s richest deposits. Driven by demand from Chinese steel manufacturers, the province’s mining industry boomed until 2014, when, in an attempt to foster a local smelting industry, Indonesia banned exports of raw nickel ore. The future of the ban is uncertain, but at present it still stands.
By the time the ban was put into place, locals already reported that runoff from strip-mines was silting up rivers and winding up in the sea, turning once-clear coastal waters red and choking off seagrass and other marine life. Requiring ore to be processed locally also creates its own problems: In a rush to build smelters, port facilities and roads were hurriedly built, adding road dust, coal ash and mine slag to the equation.
Data gathered by the expedition appears to give weight to fears that this industry would have a devastating impact on the province’s marine ecosystem.
The expedition team observed a high level of sedimentation in water near mining areas. Horizontal visibility was less than 10 meters, Estradivari said. Sediment in water blocks out light these ecosystems need to survive, and can bury coral as it settles out. “What really concerns us is the location of the nickel mining area. It is very close to the border of the Lasolo Bay Marine Park (TWAL) so the environmental impact of the mining can directly influence the health of coastal ecosystem,” she said.
One of the key finding of the expedition was nine of the 38 sampling sites (around 24 percent) had a low level of hard coral coverage. In these sites, hard coral — the building blocks of reefs — covered less 25 percent of each site. This number indicates that the coral reef ecosystem is not healthy.
The other striking finding is the proliferation of Acanthaster planci, a spiked starfish popularly known as crown-of-thorns. This coral-eating species is naturally present in reef ecosystems — but normally in low numbers.
These starfish are considered to be one of the main drivers in the destruction of Australia’s Great Barrier Reef, and an outbreak in Southeast Sulawesi could have a severe impact on reefs there. Since crown-of-thorns feeds on coral, a high number of the starfish can led to a sudden increase in coral deaths in a very short time. To make matters worse, crown-of-thorns likes to eat fast-growing corals such as those from the genus of Acropora. “There is no exact number that defines what crown-of-thorns outbreak is, but scientists agree that it is an outbreak when the feeding rate of crown-of-thorns is higher than the growth rate of the coral itself,” Estradivari explained.
The researchers found crown-of-thorns widely scattered in many sampling sites, off the Sulawesi mainland as well as in the coastal waters of small islands to the east. In some sampling sites, more than five crown-of-thorns starfish were found in a single site; in the most extreme case, a diver found 30.
Estradivari told Mongabay she can’t explain why this crown-of-thorns outbreak is happening in Southeast Sulawesi. Local villagers told researchers that they had never before seen an outbreak of the starfish, and previous expeditions have not observed them either. “Within the last two years, WWF has done six expeditions in Eastern Indonesia and this is our first time to witness a crown-of-thorns outbreak. We need further study to determine the cause of this crown-of-thorns outbreak. It could be anthropogenic causes or the warming of the sea surface,” Estradivari said.
However, Estradivari also said there are reasons for optimism: some sites are still in good condition, and others could still recover. Some locations around Wawonii Island do still have high levels of hard coral cover as well as a significant number of small hard corals. The location also hosts the schooling of unicorn fish, yellow-tailed barracuda, and other protected species such as hawksbill sea turtles, leatherback sea turtles, green sea turtles, whales, whale sharks, dolphins, dugongs, and manta ray.
Anung Wijaya, an expedition team member and a researcher for the Conservation and Rehabilitation Section of Southeast Sulawesi’s Marine and Fisheries Department said the findings of the expedition will guide recommendations for designing three groups of marine protected areas (MPAs) in the province. “To optimize the design of MPA network in Southeast Sulawesi waters, we have done a biophysics study to analyze the connectedness between MPAs,” he said in a press statement.
This year, the Governor of Southeast Sulawesi officially extended the total area of the province’s MPA. Around 21,786 hectares of Southeast Sulawesi’s waters have been designated for conservation purposes.
According to Estradivari, the expedition team will finalize the expedition report and recommendations will be announced in January 2017.
Banner image by Irwan Hermawan/WWF-Indonesia.