On a recent morning in Kampung Nelayan, a village on the northeastern coast of the Indonesian island of Sumatra, fisherman Heri Gunawan returned home frustrated and dissatisfied.
Heri uses traditional gear, a flashlight, a bucket and a plank to hunt for octopus crawling along the
shoreline. But the increasing severity of tidal flooding has made his job much more difficult.
“The catch of fish from the sea is very little nowadays,” Heri, 31, told Mongabay. “The impact of this tidal flooding has made my income drop drastically, as much as 30%.”
Heri isn’t alone. As climate change causes sea levels to rise, Indonesia, an archipelagic country of 270 million people, stands to be one of the worst affected by tidal flooding, which is when low-lying coastal areas are temporarily inundated with seawater. The phenomenon is exacerbated by erosion and the subsidence, or sinking, of coastal lands.
As many of 199 of Indonesia’s 514 cities and districts could be affected by tidal flooding by 2050, according to a recent analysis by Kompas, Indonesia’s biggest newspaper, based on data from the nonprofit Climate Central.
The Indonesian Traditional Fishermen’s Association, known as the KNTI, reported in March that 15,820 fishers across the country had been affected by tidal flooding in the past week.
Kampung Nelayan is a short boat ride from the port of Belawan in Medan, the biggest city in Sumatra. The island’s east coast, along with the north coast of Java Island, are the areas most vulnerable to tidal flooding, according to Widodo Pranowo, principal researcher at the Center for Climate and Atmospheric Research (PRIMA) at the National Research and Innovation Agency (BRIN).
The unique geological conditions in Belawan have made the problem particularly acute. The area’s land, the result of millions of years of alluvial deposits from ancient rivers and nearby Lake Toba, is still relatively young on a geological scale, Widodo said, so it hasn’t been completely compacted, rendering it vulnerable to subsidence.
“So when there is an increase in the load on the building above it, the land in the Belawan area slowly descends,” he said.
The clearing of mangrove forests to make way for oil palm plantations along the coast has also contributed to Belawan’s tidal flooding, according to Onrizal Onrizal, a forestry researcher from the University of North Sumatra.
Some 60% of the mangroves on the east coast of North Sumatra province were damaged between 1977 and 2006, according to Onrizal’s research, with the destruction continuing into the present day. As a result, two-thirds of the area’s fish species have become harder to catch.
“If the mangroves are damaged, it will have an impact on the loss of aquatic biota there,” he said.
To overcome mangrove degradation nationally, in 2020 the Indonesian government established the Peat and Mangrove Restoration Agency, known as the BRGM. The agency targets the rehabilitation of 600,000 hectares (1.48 million acres) of mangrove forest in nine provinces, including 21,370 hectares (52,800 acres) in North Sumatra.