Replete with giant clams, blue sea stars, and damselfish, the Great Barrier Reef occupies 134,634 square miles and plummets to a depth of more than 2,000 meters off the coast of Queensland, Australia. One of the seven natural wonders of the world, and in great danger, the Great Barrier Reef comprises 3,000 individual reef systems. Coral reefs develop when coral larvae fasten to submerged rocks or other hard surfaces along the edges of islands. Corals come from the phylum cnidaria, a group that contains jellyfish, anemones, and various other viscous marine invertebrates. Corals derive nourishment from both predatory and symbiotic relationships. They can catch prey with the stinging tips of their tentacles, but they also rely on algae called zooxanthellae, which use photosynthesis to acquire energy. The coral provides the algae with a protected environment, and in return, the algae produce oxygen and help the coral eliminate waste.

There are three kinds of coral reefs: fringing, barrier and atoll. Fringing reefs, the most widespread, extend seaward from the shore. Barrier reefs also hug shorelines, but witness more breadth from beaches. They typically lie farther from neighboring land masses due to an intervening lacuna of water. Atolls curve into a circular shape around a central lagoon. The reef platforms of atolls tend to emerge from the water’s surface.

The Great Barrier Reef, as its name suggests, falls into the barrier category, and contributes vibrant claws of color, underwater rock formations, eroded by sand and waves, and more than 1,500 species of fish to the Coral Sea.

A part of this planet for 500,000 years, the Great Barrier Reef bears both the wisdom and ache of old age. Encompassing over 900 islands, it has historically represented startling biodiversity—134 species of sharks and rays, ancient sea turtles, and a surplus of seaweeds. But human influence on the climate, including ocean acidification, extreme weather conditions, and rising sea levels have led to the destruction of nearly fifty percent of the Great Barrier Reef. This process of devastation is called coral bleaching. It occurs when warming water temperatures cause coral polyps to expel the algae that live inside their tissues. It is the algae that provides the coral with 90 percent of its energy. It is the algae that provides the coral with color. What once constituted a robust spectrum of textures and hues is becoming a skeletal mass in the sea. The Great Barrier Reef is the only living thing that can be seen from outer space, and it is disappearing.