Karanggeneng, Indonesia – Susanto looked at his catch after four hours of fishing – only four mullet – and shook his head in dismay.
Usually on an August afternoon he would be on a fishing boat off the Indonesian coast, catching mullet, skipjack tuna and other fish to support his family.
But this year, fierce storms and high waves have often made it too dangerous for fishing boats to leave the shore.
Instead, he is fishing off the harbor in Karanggeneng, a village in Central Java province, using a fish trap made from a large plastic bottle and a piece of string, with flour as bait.
"The fishing is tough," said Susanto, 42, who, like many Indonesians, goes by one name.
"If I only get four fish, it's not even enough to buy chilli or cooking oil," he said, adding that, in a good season, his daily catch is four times that much and earns him a healthy Rp 25,000 (US$1.63) per kilograms at market.
But good seasons are becoming a rarity for Indonesia's fishing communities.
Rough seas driven by strong winds, which scientists link to rising global temperatures, are increasingly common and treacherous, while warming waters are killing fish or causing them to migrate to cooler areas.
"In the end, fishermen will go further out to sea to cover the loss," predicted Parid Ridwanuddin, campaign manager at the Indonesian Forum for the Environment (WALHI), an independent nonprofit.
"It is full of risks because the sea weather is often extreme. Many fishermen will become victims."
More heat, more danger
Global temperatures have risen more than 1.2 degrees Celsius (2.2 Fahrenheit) since preindustrial times and are now swiftly approaching a 1.5C degrees of warming mark that scientists fear could herald a transition to far costlier and deadlier climate change impacts.
The 2015 Paris Agreement, a pact among almost 200 nations, set a goal of limiting global warming to "well below" 2 degrees Celsius (3.6 Fahrenheit) while "pursuing efforts" for 1.5C.
But with fossil fuel use still rising globally, despite pledges to slash emissions, 1.5C of warming could be passed within a decade, top climate scientists say.
They fear that could trigger irreversible ecological tipping points, from surging sea levels as polar ice melts to spiking temperatures as methane – a potent driver of warming – escapes thawing permafrost.
A hotter planet is also expected to spark more extreme weather, crop failures, species extinctions, migration and soaring personal and financial losses for many people around the planet.
Indonesia's government has predicted the country of more than 17,000 islands could suffer annual economic losses of nearly 115 trillion rupiah ($7.4 billion) by 2024 due to the effects of climate change, with 70 percent of those losses in the marine and coastal sector.
Along with driving increasingly hazardous extreme weather, global warming is also shrinking fish stocks around Indonesia, explained Yonvitner, a coastal and ocean resources expert at the IPB University in West Java.
As ocean water near the coast warms, fish – who thrive in certain temperature ranges – tend to migrate to cooler areas, while those who stay are less likely to reproduce, he said.
Yonvitner's studies on mackerel, tuna and other commonly consumed fish over the past five years show that once ocean temperatures hit 30 degrees Celsius (86 degrees Fahrenheit), fish reproduction falls.
Indonesia does not collect comprehensive data on ocean temperatures, he said, but his research estimates temperatures in the waters around the island nation now spike above that threshold every three years before settling back down again to about 29 degrees Celsius.
"If these temperature rises continue, it will certainly threaten fish stocks in the future," he said.
Heat stress also causes coral reef bleaching, when overheating coral expel the colorful algae living on them, increasing the likelihood the coral will die and destroying vital marine habitats.
Indonesia's reefs make up more than one-tenth of the world's total reef area, according to government data.
"When coral dies or undergoes bleaching, it can no longer be a place for fish to live or breed," said Sukandar, a researcher at the Center for Coastal and Marine Studies at Brawijaya University in Malang.
A report by the government's Research Center for Oceanography, published in 2020, classified nearly a third of the country's reefs as "poor" or "fair", meaning less than half of the coral covering the reefs is still alive.
Attributing some of that damage to rising ocean temperatures, the report said many reefs may have hit a "no-return point", where they have either died or will die in the near future.
"I can't imagine the condition of coral reefs in the future if the temperature continues to rise," Sukandar said.
Abandoning the sea
At Tasikagung fishing port in Rembang regency, fisherman Abdi said a decade ago he could catch 10 tons of fish in three days at sea.
To bring in the same harvest today, he estimates he would need to be out for 15 days.
"And only if the weather makes it possible," he added. He now makes so little income from fishing, he said, that he has had to sell his motorbike for cash to meet his daily needs.
"I will buy it back when I can go out to sea again," he said, hopefully.
Ridwanuddin at WALHI said his group predicts that as fish migrate further from traditional fishing areas and extreme weather makes fishing more dangerous, Indonesia fishermen will see their incomes drop substantially.
Kurniawan Priyo Anggoro, of Central Java's Department of Marine Affairs and Fisheries, acknowledged the magnitude of the challenges facing Indonesia's marine sector in the future, from both climate change and overfishing.
He said his department is working on guidance to help make the province's fisheries more sustainable, for example by detailing the best times of year to catch certain species, so fishermen can figure out exactly when they need to go out and avoid unnecessary trips into storms or choppy water.
The government also plans to provide fishing communities with free updated gear to improve catches – such as gillnets, vertical panels of netting that hang from a line – and training on how to turn their catch into processed fish products worth more at market.
For now, the growing struggle to support their families is causing a growing number of fishermen to leave the industry.
Data published last year by Indonesia's central statistics agency show the number of fishermen working in the country has dropped by more than 10 percent in the past decade.
That's evident in the regency of East Lombok, once known for its thriving squid processing industry with more than 20 plants preparing squid to send to Japan, Taiwan and other countries.
As catches have dried up and fishermen gone to find other work, "it's gone now. All the stalls are closed," said fisherman H. Amin Abdullah.
Because families in East Lombok feel the sea can no longer provide a livelihood, nearly all of them now have members who work outside Indonesia and send money home, Abdullah said.
"Young people aged 18 and above go abroad. Why? Because fishing is no longer profitable," he said.
"It's hard to know what to expect from the sea if the temperature keeps getting hotter."