Here are 15 things every person should know about the state of the ocean and the crises it faces.

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1. Who should read SILENT SEAS?

SILENT SEAS is written for the general public and the ocean conservation community. For those who don't read scientific journals or the latest articles yet are concerned about the state of the ocean and its impact on human well-being, this book will educate, enlighten, and activate. While based on current science and up-to-date ocean policies, the book focuses on human stories, the kind that engage and inform the reader. 

 

2. How much of the oxygen we breathe comes from the ocean?

More than half. Scientists estimate that 50 to 80 percent of the oxygen we breathe comes from the ocean, most of it from microscopic drifting organisms called phytoplankton. The ocean is the planet's largest living source of breathable air, and it is weakening. Warming seawater holds less oxygen, and the open ocean has already lost about 2 percent of its oxygen since 1950. (Learn more in Silent Seas: Chapter 4, "Why It Matters," and Chapter 21, "Healthy Oceans.")

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3. Is the ocean impacted by climate change?

Yes, and it is paying a price. Since the Industrial Revolution, the ocean has absorbed about 90 percent of the excess heat from human activities and industry, and roughly a quarter of the carbon dioxide we emit each year. Without that, the air would be far hotter. But absorbed carbon dioxide is changing the water itself. Surface seawater is now about 30 percent more acidic, which makes it harder for corals, shellfish, and tiny plankton to build their shells and skeletons. (Read more in Silent Seas: Chapter 13, "Global Warming.")

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4. How much damage have coral reefs suffered?

In the past several years, 84 percent of the world's coral reefs suffered heat stress strong enough to cause bleaching and some coral die-offs. Bleached coral can recover if the water cools, but widespread die-offs have been recorded in parts of the Caribbean, the Red Sea, and the Great Barrier Reef. Scientists warn that reefs are entering an era of near-annual bleaching, which poses a danger to fish stocks and ocean biodiversity. (Read more in Silent Seas: Chapter 3, "The Holiday from Hell," and Chapter 13, "Global Warming.")

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5. Are we running out of fish?

Not everywhere, but the warning signs are clear. The UN Food and Agriculture Organization now counts nearly 40 percent of fish stocks as overfished. Yet about 73 percent of the global catch still comes from sustainably managed stocks, which shows that good management works. Overfishing is often the result of weak enforcement and destructive methods, such as bottom trawling, that scoop up everything and tear up the seafloor where many fish and shellfish live and feed. (Read more in Silent Seas: Chapter 5, "Overfishing," and Chapter 6, "The Ravaged Seafloor.")

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6. How much fish is caught illegally?

Roughly one in every five wild-caught fish comes from illegal, unreported, or unregulated fishing, worth an estimated $23.5 to $36.4 billion a year. These boats steal from law-abiding fishermen and coastal communities, and many switch off their tracking transponders to evade authorities. Satellites can now find them. But penalties are often so light that a fine is simply a cost of doing business. (Read more in Silent Seas: Chapter 15, "Eyes in the Sky," and Chapter 18, "The Ocean's Legal Eagles.")

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7. How much plastic is in the ocean?

The world now makes about 460 million tons of plastic a year, twice as much as in 2000. Around 1.7 million tons flowed into the ocean in 2019 alone, adding to roughly 30 million tons already in the sea, and other studies put the yearly flow higher. Most of it arrives by river. About 1,000 rivers carry roughly 80 percent of what rivers deliver, which makes the source, not the open sea, the place to stop it. (Read more in Silent Seas: Chapter 7, "The Plastic Tsunami.")

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8. What are ocean dead zones, and how many are there?

A dead zone is water so low in oxygen that most marine life cannot survive. Fertilizer and sewage washing off the land feed huge algae blooms. When the algae die and decay, they consume oxygen. Scientists have documented at least 500 coastal dead zones, up from fewer than 50 in 1950. The best known sits in the Gulf of Mexico, fed by farm runoff from the Mississippi River basin. (Read more in Silent Seas: Chapter 1, "The Gulf Coast," and Chapter 8, "Our Toxic Oceans.")

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9. Isn't the ocean already protected?

Partly, on paper. About 10 percent of the ocean now lies within a protected area, but only about 3.3 percent is fully protected, where fishing and other extractive activities are banned. Governments have pledged to protect 30 percent of the ocean by 2030. Many protected areas are simply lines on a map without any enforcement. In the United Kingdom, about 90 percent of the 377 marine protected areas still allow bottom trawling. Protection works, but only when someone enforces it. (Read more in Silent Seas: Chapter 14, "Forlorn Hope," and Chapter 16, "A High Seas Treaty.")

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10. Who is hurt most when the ocean declines?

More than 3 billion people get at least a fifth of their animal protein from fish and other aquatic foods, and the UN estimates that about 600 million people earn a living from fisheries and aquaculture, most of them in small-scale operations in developing countries. When a fishery collapses due to illegal overfishing or a coastline degrades, those families lose food, income, and often a way of life. Silent Seas follows their stories from Louisiana to Senegal to Alaska. (Read more in Silent Seas: Chapter 2, "Another Ocean Tragedy," and Chapter 4, "Why It Matters.")

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11. Is tourism part of the problem?

Often. A study that tracked more than 700 scuba divers recorded about 5,000 contacts with the reef, and 41 percent caused visible damage. In Florida, 96 percent of adult manatees carry scars from boat strikes. Sunscreen contains chemicals toxic to marine life, and researchers estimate that 6,000 to 14,000 tons wash onto reefs each year. But well-managed tourism can also help pay for ocean protection. (Read more in Silent Seas: Chapter 11, "Loving the Ocean to Death.")

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12. Do ships really kill whales?

Yes, and the danger is global. A 2024 study found that a large majority of shipping lanes overlap with the migration routes of blue, fin, humpback, and sperm whales, yet only about 7 percent of the highest-risk areas have any measures to protect them. Mandatory measures are rarer still. In the North Atlantic, four of the roughly 370 remaining right whales were known to have been killed by ships in 2024. (Read more in Silent Seas: Chapter 10, "The Ocean as a Dangerous Highway.")

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13. How do invasive species threaten islands and the sea?

Rats, cats, and goats arrive on ships and do lasting damage. Invasive species were a major factor in about 60 percent of plant and animal extinctions, and about 90 percent of the extinctions attributed mainly to invasive species happened on islands. The harm can also reach the reefs. Rats eat seabird eggs and chicks, and seabird droppings fertilize nearby coral reefs, so losing the birds can starve the reef fish too. Invasive species cost the world more than $423 billion in 2019, a cost that has at least quadrupled every decade since 1970. (Read more in Silent Seas: Chapter 9, "I Smell a Rat, a Cat and a Goat.")

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14. Is toxic waste still being dumped into the ocean?

Yes. Some mines pump toxic waste straight into the sea. The Ramu nickel mine in Papua New Guinea discharges close to 14,000 tons a day into the ocean. In 2019, a pump failure released about 200,000 liters of acidic slurry, turning the water red. (Read more in Silent Seas: Chapter 8, "Our Toxic Oceans.")

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15. Is it too late to save the ocean?

No. The ocean can recover when people act. At Cabo Pulmo, Mexico, villagers closed their reef to fishing and guarded it themselves. Within a decade, fish biomass there rose 463 percent. A 2025 study found little to no industrial fishing inside strictly protected areas. In September 2025, the first global agreement limiting harmful fishing subsidies took effect, and the High Seas Treaty entered into force in January 2026. The tools exist. The work now is enforcement and funding. (Read more in Silent Seas: Chapter 21, "Healthy Oceans," and the Epilogue.)

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