Rachel Carson is best known for her seminal work Silent Spring (1962), which brought critical attention to the havoc being wrought by pesticides on the environment. But by then she had already published a number of other well-received works, including The Edge of the Sea, a natural history of the shore and its flora and fauna. A marine biologist by training, Carson had a deep affection for shoreline communities of all sorts, and this work is suffused with her enthusiasm for each variety of coastal marine life. Central to the chapter entitled "The Coral Coast" is her fascination not only with the creatures who live among the coral, but with the living organisms who built the reefs themselves.

Coral reefs are built by communities of tiny coral polyps, living animals that extract calcium from the seawater to form a carbonate exoskeleton for support and protection. It is the accumulating structure of these exoskeletons that make up the reef, formed in many cases over the course of hundreds of thousands of years, and creating the underwater environment in which much of the marine life we know today evolved.

The coral polyps live in a symbiotic relationship with simple algae called zooxanthellae, which live inside the exoskeleton with the coral, and exchange nutrients, waste products, oxygen, and carbon dioxide. It is these algae that give coral its exquisite palette of colors.

Coral reefs are known as the "rainforests of the sea" because they provide the habitat for some 25% of marine species, including over 4000 species of fish.1 They also provide coastal protection from violent storms, contribute substantially to the tourism economy of many reef countries, and, like terrestrial rainforests, are the source of many pharmaceutical ingredients. And they are aesthetically magnificent. According to a popular field guide, a reef's "infinite diversity and beauty make it an almost mystical experience."2

Coral reefs are under assault around the globe. A 2004 study found that in the past half-century, 20% of the world's reefs have been permanently destroyed, an additional 24% face imminent collapse, and yet another 26% face longer-term collapse.3 The causes are many, but primarily two: warming temperatures and ocean acidification, both ramifications of climate change. Even a very slight warming of the seawater – often as little as 1° Celsius (1.8° Fahrenheit) – can result in coral bleaching,4 in which the algae are expelled from the reef, leading to the rapid death of the coral. And the absorption by the ocean of some of the excess carbon dioxide being pumped into the atmosphere increases its acidity, interfering with the formation of the calcium carbonate that forms the reefs.

Global water temperatures began a steady rise in the 1980s, accompanied by coral bleaching on a scale never before approached. In one year alone (1998) the world lost 16% of its reefs.5 In the Caribbean, eight coral species have lost 30% of their extent since this warming trend began. In other parts of the world, species have fared far worse. Fish living among the reefs have suffered greatly increased predation, presumably because they are far more conspicuous against the stark white of the dead reefs.6 Entire magnificent underwater landscapes have been wiped out. And the warming continues.

As the plight of the world's reefs becomes more apparent, organizations and governments are beginning to step in. Global initiatives like the World Heritage Convention, and more local tools like the U.S. Endangered Species Act, may ultimately play an important role in staving off the complete loss of the earth's reef systems. Florida's two most critically endangered coral species, the elkhorn and staghorn corals, were listed as endangered in 2006, the first time corals had been placed on that list. Such protections could at least help reduce harm from other threats such as ship strikes, careless tourism, blast fishing, and offshore oil production. But to a large extent, the fate of the world's reefs will depend on how quickly appropriate action is taken against climate change.

For Carson, the coral islands of the Florida Keys reverberated with the whole deep history, past and ongoing, of the life forms intrinsic to their existence. She could not have imagined how perilous the next chapter in that long history might be, nor that future readers might one day page through her work with more nostalgia than wonder.

1 Mulhall Marjorie. "Saving the rainforests of the sea: An analysis of international efforts to conserve coral reefs." Duke Environmental Law and Policy Forum, 2009: 19(2) pp. 321-351.

2 Kaplan, Eugene H.; Peterson, Roger T.; and Kaplan, Susan L. A Field Guide to Coral Reefs: Caribbean and Florida (Peterson Field Guide). New York: Houghton Mifflin Co., 1982.

3 Eilperin, Juliet. "Yes, the water's warm . . . too warm." The Washington Post, July 15, 2007: p. 4.

4 Goreau, TJ; Hayes, RL; et al. "Elevated Sea Surface Temperatures Correlate with Caribbean Coral Reef Bleaching." Global Coral Reef Alliance. http://www.globalcoral.org/elevated_sea_surface_temperature.htm.

5 Davidson, Mary Gray. "Protecting Coral Reefs: The Principal National and International Legal Instruments." Harvard Environmental Law Review, 2002: 26(2).

6 Coker, DJ; Pratchett, MS; and Munday, PL. "Coral bleaching and habitat degradation increase susceptibility to predation for coral-dwelling fishes." Behavioral Ecology, 2009: 20(6), pp.1204-1210.