Blast fishing is deadly for fish and dangerous for fishers. If a bottle explodes too soon, you could lose a hand, an arm, or a life. A fisher died this way two days before I arrived here at the Danajon Bank, 20 miles east of Cebu island, in a region of the Philippines with a long history of destructive fishing practices: explosives, cyanide to flush fish out of coral crevices, nets so fine they catch anything that moves.

All of these methods are illegal, all still in use. They are a cumulative disaster for coral reefs, a more instantaneous depletion of marine life than the slower-burn tragedies of declining fish stocks, pollution, and climate change.

I see a figure in the distance, gleaning in the dynamited ruins, and swim to him. He’s wearing a long-sleeved shirt, trousers, and a hood over his head, with holes for his eyes and mouth. He has a battered pair of goggles over his eyes and pieces of plywood strapped to his feet for fins.

“Jellyfish?” I ask, pointing to his hood. My boat driver had told me of tangling with a box jellyfish in these waters. He just had time to scream for help before passing out from the pain of stinging tentacles. He showed me the welts on his arm and stomach, still vivid after 15 years.

“Sun,” the diver answers.

To collect enough food for his family, he tells me, he often has to stay out half a day in the burning heat, combing the reefs. He tows a polystyrene box to hold whatever he catches: whelks, abalones, sea urchins, crabs, fish if he’s lucky. He uses a hook in one hand and a spear in the other. He pokes, prods, levers, and hacks at the coral. I see a sudden puff of black ink as he spears a cuttlefish.

He picks up a sea cucumber and hands the warty creature to me. A tassel of white threads adorns its rear end. Quicker than I can register, the threads shoot out and wrap around my hand, sticking to my skin like superglue—the animal’s reaction to being disturbed. I disentangle the creature, and it goes into the catch box.

The gleaner’s laborious search for food is something that is happening across the Philippines, and throughout the Coral Triangle, as ever increasing numbers of people hunt for ever decreasing quantities of fish. For millions of Filipinos, the sea is essential to survival. In the Danajon region, three-quarters of households depend on fishing for food and livelihood. They saw catch rates decline by a factor of 10 in a generation.

A quarter of the fish caught in Danajon come from illegal and destructive practices. Subsistence fishers, living at or below the poverty line, are driven by desperation to use such methods. Filipinos have the phrase kapit sa patalim, or “grasp the blade.” A desperate person will clasp even the sharp edge of a knife—breaking the law, risking arrest, destroying the reefs that are their lifeline.

In some months of the year, gleaners can gather only about nine meager ounces of seafood an hour from the impoverished reefs. I watch this man suck another breath, flail his plywood fins, and descend.

I am gleaning too—hoping to learn how coral reefs might be preserved at a time not just of increasing exploitation but also of human-driven changes in the very ocean itself. Warming seas, acidifying seas, rising seas—these are the darker shadows that fall across the world’s coral reefs.

Off the coast of Palawan, the fingerlike island on the western flank of the Philippines, I caught a preview of what’s coming. I dived in a sepulchral world of bleached corals. Sea temperatures had exceeded the threshold at which coral polyps part company with the symbiotic algae that give them their kaleidoscopic colors. The corals were ice white. Streams of slime wafted from their dying heads. Even the fish seemed dazed in that monochrome landscape.

Some coral scientists say that mass bleaching events, which used to happen once every few decades, soon may happen every year, as the concentration of atmospheric carbon dioxide continues to increase. What rising sea temperatures don’t kill, acidification will. Reefs will reach a tipping point where the carbonate coral structure starts to dissolve faster than it can be formed. When that happens, they will begin to disintegrate. The most diverse ecosystem in the ocean—a planetary feature for 240 million years—will start to disappear.

Can this dystopian story have a different ending? Or at least be delayed? Humans are engaged in the biggest gamble of all time, and the stakes could not be higher.

There are two ways to respond to a diminishing resource: Ease up or double down. Filipinos have done both. The bomb-cratered moonscape I saw at Danajon Bank is the end result of one approach: destructive overfishing of reef ecosystems. But at Dauin, a municipality on Negros island, I saw a different legacy, one of reef protection that has eased pressure on marine life and sustained a living for communities on the coast.

The approach was pioneered by Angel Alcala, a Filipino biologist who has championed the creation of small, community-managed marine protected areas (MPAs). Often the prime reason for creating these sanctuaries is to preserve biodiversity, but for Alcala the main focus is to benefit fisheries. “Filipino people are fish-eaters,” Alcala tells me when I meet him at the research center he leads at Silliman University, just north of Dauin. “To maintain that, there need to be marine reserves.”

Alcala started in the early 1970s with two prototype reserves: one near an island that was inhabited (Apo, off the coast of Dauin) and one near an island that was not (Sumilon, near Cebu). All forms of harvesting were prohibited.

The results were spectacular. In 10 years, fish biomass for some species in the sanctuaries—namely groupers, snappers, and jacks—increased at least sixfold. As the density of fish inside the reserves increased, fishers reaped the benefit through the phenomenon of spillover: Fish “spill over” reserve boundaries into waters where they can be legally caught. The idea that no-take sanctuaries could replenish fish stocks on nearby exploited reefs offered a bright speck of hope in an otherwise dismal outlook for coastal fishers.

Apo Island’s success caught the attention of Rodrigo Alanano, who was elected Dauin’s mayor in 2001. Alanano decided to increase the number of marine protected areas along the Dauin coastline. He could do this because municipalities have jurisdiction over their coastal waters out to 15 kilometers, or 9.3 miles.

I ask him how he persuaded subsistence fishers to give up a portion of their traditional fishing grounds. “I told them we needed to have breeding grounds as well as fishing grounds,” he says. “I told them, ‘If you have a sanctuary, populations will grow, and some fishes will get out of the sanctuary and those ones are for you. The reserve will be a breeding ground for fishes now and forever, for you and for the future.’ Later on, I told them, it would become a diving spot, and there would be an income from that.”

Still, getting fishers to accept an immediate loss for an uncertain gain was no easy matter, and many coastal dwellers opposed the sanctuaries. Alanano was served with lawsuits and received death threats. He shrugs at the memory. “When I became mayor, I gave my life for this profession,” he says.

“What made you so passionate?” I ask. “You’re not even from a fishing family.”

“I am a mining engineer,” he replies. “I worked for mining companies for 12 years before entering politics. We destroyed mountains. We used toxic chemicals that flowed out to sea. I am an experienced destroyer of the environment. I am licensed to destroy. What I experienced is that once you destroy the environment, no human being can put that right again. It cannot be put back for your children. And when you kill the last fish, you will realize you can’t eat money.”

His arguments prevailed. During Alanano’s nine years as mayor, he increased the number of MPAs along Dauin’s coastline from four to 10. I dived in some of them. Though small, they protect wondrous creatures. At one site I watched scores of slender garden eels rise from their holes in the seabed and sway as if hearing the music of a snake charmer.

As Alanano foresaw, such sights are a drawing card for tourists, and Dauin has become a popular dive destination, as have dozens of other sites across the 7,641 islands in the Philippines. Most of Dauin’s MPAs are referred to by the names of fish species that serve as their celebrity attractions: Nemo/Clown Fish MPA, Mandarin MPA, Frog Fish MPA, Ghost Pipe and Sea Horse MPA.

As tourism has flourished, fishers have seen opportunities to switch from catching fish to providing services. In Oslob, a town on the coast of Cebu, few members of the fishers association fish anymore. They earn a handsome living enabling tourists to swim with whale sharks. Near Puerto Galera, on the island of Mindoro, I watched snorkelers being towed out to see giant clams by fishers in small outrigger canoes powered by chain saw and lawn mower engines.

In Dauin, several fishers have retrained as dive masters. Amado A. Alar II runs Bongo Bongo Divers, down a side road from a Chooks To Go fried-chicken house. He tells me that when Dauin’s MPAs were being established, some fishers refused to accept the loss of their fishing grounds. They cut the ropes of the buoys that marked the sanctuary boundaries, slipped into protected areas at night to catch fish, and came to blows with the bantay dagat—municipally appointed sea wardens—if they were caught.

But when the fishers saw their catches increase, they changed their tune. “Slowly, slowly the people understand—‘Ah, that’s why it is like this,’ ” Alar says. “Now they will protect the sanctuary if they see someone fishing there. They understand that we have a nursery here.”

This nursery effect is now considered one of the key benefits of MPA networks. Larval fish disperse from reefs in protected areas to unprotected reefs, providing replenishment.

Rene Abesamis, one of Alcala’s colleagues at Silliman, has studied the process in Dauin’s MPAs. He chose the vagabond butterflyfish for his research and found that its larvae can drift up to 23 miles in monsoon winds and strong currents before settling into a new reef habitat.

Knowing that fish on the local reef may have come from neighboring sanctuaries has a powerful effect on people. “It tells them that they are part of the same ecological network, even if they belong to different municipalities,” Abesamis says. “It tells them their efforts are connected.”

Mutual replenishment is the logic behind efforts to scale up MPAs into a nationwide network. Philippine law stipulates that 15 percent of coastal municipal waters must be protected within no-take MPAs. There are now more than 1,600 of them throughout the country. Unfortunately, most are tiny and not well managed—mere “paper parks.”

Only 3 percent of the country’s coral reefs are protected, Alcala says, explaining, “We need 20 to 30 percent. It’s a question of empowering local communities.” And giving them the resources to protect the investment they have made. Even sanctuaries that are properly cared for by their communities are susceptible to poaching. The COVID-19 pandemic, which has devastated tourism, also has made marine protections precarious. Even local people, grasping the blade of desperation, have entered protected areas to feed their families.

But poaching by outsiders is a greater threat, and a growing problem across the Philippines. With fast boats and scuba gear, professional poachers can strip a sanctuary in a night, Darrell Pasco tells me. Pasco works in coastal resource management for the island of Siquijor, a dozen miles from Dauin. One of Siquijor’s MPAs was poached four times in a single year. The intruders come at night, during fiestas, or at times of bad weather, when there are fewer eyes watching, he says. They carry weapons. How can Siquijor’s bantay dagat, who earn a pittance, oppose such people?

Siquijor, as much as anywhere else, needs marine sanctuaries to bolster the island’s fisheries. As high-value fish such as grouper and snapper have become scarce, species that were formerly considered trash fish have become standard fare. Damselfish—darting cobalt-blue beauties with mango dipped tails—were never eaten, Pasco says. Now they sell for a premium in the market, alongside such delicacies as sea anemones cooked in coconut milk, spider conchs, sea cucumbers, sea urchins, and seaweeds that look like clusters of green pearls.

I saw the struggle that Siquijor’s fishers face when I slipped into the silky sea one morning to watch a group of men haul up a fish trap, or bubu, from the seabed about 250 feet below us. Slowly it rose, a 15-foot-long woven basket spacious enough that I could have swum pirouettes inside it. The pattern of its bamboo weave was intricate, the work of skilled hands. As seven men heaved the bubu onto the deck of their banca—the traditional double-outrigger boat of the Philippines—I peered inside, looking for the harvest that should have been there, for the baited trap had lain on the seabed for a week. A fisherman reached in and lifted out a single triggerfish—a paltry return for a week’s deployment.

The next bubu I watched being hauled up had no fish at all. “Mingaw,” one fisherman called, as the trap broke the surface. Empty. I winced as small jellyfish and broken arms of sea anemones fell from the trap and stung my skin. And I winced for the dashed expectations of the men and their families. Bubu fishers may earn as little as a dollar per trap per week. Their households are typically on the poverty line or below it, as is 60 percent of the country’s coastal population.

Like Dauin’s mayor, Pasco has been threatened over his efforts to expand MPAs and deter poaching. To guard his property, he keeps a watchdog and sleeps in a hut outside his house. “I’m afraid for my security and my family’s security, but I’m still doing my job,” he tells me.

There is no other option, he says. “We have to give an honest and profound education for every Filipino, that it is up to us to take care of the ocean because we get almost everything we need from the ocean. If we don’t do that, the time will come when we will have no more fish to catch, and we will only see fish in books and on the internet, not in the ocean.”

Tourism helps alleviate pressure on dwindling fish stocks, but not every place can be a dive hot spot. Another way of relieving the demand on reef ecosystems is for fishers to take up alternative livelihoods such as marine farming. At a remote atoll in the Sulu Sea I met families living on bamboo platforms in reef lagoons, drying seaweed. The algae they farm produce carrageenan, a polysaccharide used as a stabilizer in medicines, toothpaste, pill capsules, cosmetics, and other products. Thousands of Filipino families have become seaweed ranchers.

In the islands of the Calamian Group, at the northern tip of Palawan, people are learning how to ranch sea cucumbers. I helped release dozens of juveniles the size of my little finger from net cages so they could free-range across warm estuarine flats. In two months they will reach the size of fat sausages. When dried, sea cucumbers sell for more than $30 a pound, 10 times more than grouper.

There is abundant evidence that reefs regenerate when human pressure is removed. The preeminent dive site in the Philippines is Tubbataha Reefs, a national park and UNESCO World Heritage site in the center of the Sulu Sea. Here I saw barrel sponges large enough for a person to curl up inside. I watched confetti clouds of fish—orange, purple, green, yellow—floating above slender coral branches, while gray reef sharks slept on coral sand beneath. An octopus unspooled its arms and, with an instantaneous color change from fawn to charcoal, jetted away. Exceptional today, these reefs were all but destroyed by blast fishing in the 1960s. Strict enforcement of no-take rules has redeemed them.

But will they survive bleaching and other climate pressures? Most researchers think not. It is projected that by 2050 more than 90 percent of the Coral Triangle’s reefs will be critically threatened by climate impacts. As reefs fail, food insecurity in the region will become calamitous. How will coastal dwellers survive?

The Philippines has stared into an apocalyptic future of degraded reefs and depleted seas. It has recognized the choice it has to make: Seize the moment of change, or grasp the blade of crisis. In the past four decades, communities have made hard choices to forgo fishing everywhere for the ability to catch fish somewhere. They have realized that visitors will pay to see thriving reefs. They have become committed guardians and stewards of an incomparable ocean realm.

But these changes alone will not preserve the reefs on which millions depend. Ocean warming is locked in. Ocean acidification is locked in. Extreme weather is locked in. What will local efforts avail in the face of intractable planetary forces?

I ask coral reef biologist Wilfredo Licuanan, a professor at Manila’s De La Salle University, what reason he or anyone could have for optimism.

“We have to delay the inevitable long enough for some glimmer of hope, some solution that might come up that is not yet visible,” he says. “I want to be able to at least look my students in the eye and say, ‘I’m trying.’ I’m pessimistic, but I’m trying. If I fail, I don’t give up. I try again.”