Coral Bleaching

From 2023 to 2025, coral reefs experienced their fourth global bleaching event

Heat stress from the 33-month-long event impacted about 84.4% of the world's coral reef area across waters in at least 83 countries and territories, making it the largest such event to date. Due to climate change, about 90% of coral reefs are expected to undergo bleaching annually by 2050, leaving insufficient time for recovery during the winter months between bleaching events.

Explore a world map of coral reefs and the extent of coral bleaching

The Allen Coral Atlas provides imagery of shallow water reefs, along with maps of potential bleaching events, bleaching alert areas, and bleaching hotspots derived from satellite imagery of whitening. Coral reefs are most prevalent in the Indo-Pacific, the Caribbean, the Red Sea, and the tropical coasts of South America and Africa.

How climate change threatens coral reefs, including via warming and acidification

Increasing ocean temperatures disrupt the symbiotic relationship of corals and algae, causing the former to bleach and weaken, and strengthen storms that can destroy reef structures. Higher greenhouse gas emissions increase dissolved carbon dioxide levels in ocean water, triggering a series of reactions that consume carbonate, a key ingredient in coral reef construction.

Explore the history, structure, and species of Australia's Great Barrier Reef with this interactive journey narrated by Sir David Attenborough.

Watch how coral bleaching resembles an organism's immune system attacking itself

Microorganisms called zooxanthellae are in a symbiotic relationship with coral polyps and provide them with food created through photosynthesis. When ocean temperatures or sunlight exceed an optimal range, zooxanthellae release harmful chemicals that irritate coral cells. To protect themselves, corals sacrifice their food source and expel the colorful microorganisms, becoming white.

Overview: All about coral reefs

Coral reefs aren’t just vibrant underwater landscapes; they are also some of the most biologically diverse ecosystems on Earth. The National Oceanic and Atmospheric Administration (NOAA) offers a comprehensive guide that explores coral reefs in...

A simple infographic explaining how coral bleaching works

When corals are stressed by changes in conditions such as temperature, light, or nutrients, they expel the symbiotic algae living in their tissues, causing them to turn completely white.

Scientists explore innovative solutions to protect coral reefs

As coral reefs are under increasing stress due to climate change, pollution, and other factors, scientists are employing creative solutions to save these crucial marine ecosystems. This National Geographic article explores the various scientific...

Scientists are using CRISPR to crossbreed heat-resistant corals amid warming reefs

Inside Australia's National Sea Simulator, coral hybrids are genetically engineered to resist the widespread coral bleaching caused by rising global temperatures. Early trials have developed groups with survival rates up to 34 percentage points higher than nonhybrids. (Some readers may experience a paywall.)

Why are coral reefs important?

Coral reefs are vital ecosystems that millions of people and countless species depend on. This two-minute video from London's Natural History Museum looks at the ecological and economic significance of coral reefs, including their biodiversity and...

Take an interactive tour through Australia's Great Barrier Reef

This adventure offers spherical panoramas of marine wildlife, including manta rays, loggerhead turtles, and bottlenose dolphins. The shipwreck of a luxury passenger vessel and coral reef systems are also explored with underwater audio recordings of the environment.

View a collection of glass sculptures of corals threatened by fishing and deep-sea mining

In "Depicting Dark Waters," British sculptural model maker Alice Baker depicts European cold-water corals, which make up 65% of all known coral species, to raise awareness of deep-sea ecosystems threatened by commercial and industrial activities. The project involved a collaboration with marine biologists from the Netherlands and Sweden.

The world's largest coral, as seen from space

The world’s largest individual coral colony—measuring over 100 feet wide and 100 feet long—was discovered in the Solomon Islands. This coral is so large it can be seen from space, and is estimated to be between 300 and 500 years old. The coral's size and health provide hope amidst a global coral bleaching crisis, wherein three-quarters of coral reefs have experienced significant bleaching in recent decades. See the photos from space and learn more here.

Fish populations in the Great Barrier Reef have increased after installing waterproof speakers on the ocean floor that played recordings of sounds from healthy coral reefs.

An overview of the Coral Triangle, which contains about 76% of global coral species

Spanning the waters of Indonesia, Malaysia, Papua New Guinea, the Philippines, the Solomon Islands, and Timor-Leste, the region contains more than 600 coral species and over 2,200 of the world's coral reef fish species. It sustains 120 million people with food and other resources, as well as a $12B yearly tourism industry.

Learn how humans can protect coral reefs

When diving and snorkeling in environments containing reefs, avoid touching reefs, anchoring on them, or using sunscreen with active ingredients harmful to marine life. Properly recycling and disposing of trash in bins helps reduce microplastics and chemicals that can run off into wastewater and into the oceans.

Fish populations in the Great Barrier Reef have increased after installing waterproof speakers on the ocean floor that played recordings of sounds from healthy coral reefs.

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.

Can coral live in cold water?

Dive deep beyond the sunlit coral reefs, and you'll discover a world of deep-sea corals. This article from the National Oceanic and Atmospheric Administration (NOAA) explores the ecosystems of deep-sea corals found way below the water's surface....

Artificial coral reefs have been 3D printed from nontoxic, biodegradable terracotta clay, which coral polyps have used as a foundation for rebuilding marine ecosystems.

Watch a time-lapse of hard coral growth, which forms coral reefs

Over several weeks in an aquarium, these staghorn coral polyps grew and produced new polyps as they deposited calcium carbonate, which forms the basis of coral reefs. At the 0:28 mark, you can see coral growth healing a damaged branch.

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

Even in nature reserves, climate change is driving rapid ecological collapse

Studies show a dramatic decline in insect populations, resulting in cascading global biodiversity losses across non-insect species. The balances in tropical ecosystems are the most affected by climate change.

Corals are themselves not coral reefs—the term refers to the tiny marine invertebrates that build the rigid reef.

Explore the animals that populate the depths of the ocean, from fish and coral in the first few hundred feet, all the way down to the bottom of the Mariana Trench.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

Why no aquarium has a great white shark

Historically, great white sharks die very quickly in captivity—with the exception of the Monterey Bay Aquarium's successful attempt in 2004. The aquarium held a four-year-old great white for six months. Before that, the longest stint was 16 days. The creatures can only breathe if they are moving forward, making survival difficult in a small tank.

Watch a 1986 television special about the discovery of the ozone hole

The groundbreaking discovery of the Antarctic ozone hole in the mid-1980s marked a critical turning point, galvanizing international action to address the ozone-depleting properties of chlorofluorocarbons, which had been identified about a decade earlier. This environmental crisis was brought vividly to public attention through media pieces like this one.

An invasive, tree-killing beetle may threaten large swaths of Australia

A Curtin University study warns that large parts of Australia, including major cities and farming regions, could be highly vulnerable to the fast-spreading polyphagous shot hole borer, which releases a fungus that can starve trees of nutrients. The tiny insect has already caused severe damage across the Perth metropolitan area.

The harsh realities of the Great Pacific Garbage Patch

Misleading images and narratives have caused the public to believe that the Great Pacific Garbage Patch is simply a large clump of floating trash in the ocean. Instead, a more apt description would paint it as a dispersed "soup of microplastics" that severely impacts marine life and the fishing industry. Read for a greater understanding of how the GPGP came to be, and the measures that need to be taken for a cleanup.

Tracing the history of the philosophy of human extinction

Global catastrophe is at the center of much contemporary debate over climate, war, science, technology, and more, and our period is marked by a lurking sense everything we know—including the human species—could end overnight. It wasn't always...

What's happening to the snowy owl?

This article explores the alarming decline of snowy owls in the Arctic. Once abundant in these northern regions, the snowy owl is now classified as "vulnerable" by the International Union for Conservation of Nature (IUCN). The adult population...

Biosphere 2 gradually transformed into a lab modeling environmental disasters

Built to establish a self-sustaining habitat, the privately funded facility was taken over by Columbia University in 1995. Closed-system experiments were halted in favor of investigations focused on the effects of climate change, which continued after B2 was donated to the University of Arizona in 2011.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

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Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

This real-time tracking of the hantavirus cruise ship outbreak in May 2026 offers a unique glimpse into the global reach of the outbreak and whether the virus sickened passengers and their communities around the world.

The Great Salt Lake's distinct dual coloration results from high-salinity organisms that only live in the northern portion and produce a purple protein.

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In 2018, 26-year-old missionary John Allen Chau was killed by tribesmen after attempting to reach and evangelize on India's isolated North Sentinel Island

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