Introduction to Corals and Coral Reefs
Coral reefs are often referred to as the rainforests of the sea. Given their immense biodiversity, confined to relatively little space, perhaps the reference should really be the other way around: rainforests are the coral reefs of the land!
At the level of phyla—the broadest taxonomic organization in the kingdom of animals (kingdoms being the major groupings of animals, plants, fungi and protists)—coral reefs harbor 33 of the 38 known animal phyla—more than any other ecosystem on the planet. By contrast, tropical rainforests host only 8 phyla. Some rainforests may have more types of species, but coral reefs harbor a greater overall diversity of life. Estimates range from 100,000 to greater than one million species living on coral reefs.
Much has been written on the beauty, color and splendor of coral reefs. They evoke a range of visual images and associations: from clear blue waters and lazy days under the sun—to excitement in exploring the unknown—unfamiliar animals and life forms, thoughts of adventure, shipwrecks and sunken treasure. Perhaps more importantly, they provide resources for millions of coastal people worldwide – the only readily available source of protein, and crucial livelihoods. Corals and related animals also provide a cornucopia of pharmaceutical compounds, with new cancer treatments and wonder drugs being discovered regularly.
But unfortunately, the plight of coral reefs is now equally renowned. Over only the course of one human generation, most coral reefs have declined around the world. The causes include a range of insults occurring as a consequence of our ever-expanding population, especially along our coastal zones. For example, of the 17 mega-cities around the world (i.e. those cities containing more than 10 million people), 14 occur within the coastal zone. Not all of these cities are adjacent to coral reefs, but most between the tropics of Cancer and Capricorn are—especially in Asia—and theyrely upon the ecosystem services of coral reefs to some important degree—either for products, shoreline protection or tourism revenue. The Millennium Ecosystem Assessment found that within the coastal zone, the vast majority of people live in close proximity to reefs1.
We are adding population to coastal lands, and many of these coastal people are taking more than our ecosystems can produce, and mismanaging their by-products and wastes. Threats of over-fishing, excessive sedimentation from deforestation and coastal land transformation, untreated sewage, unregulated agriculture and other forms of mismanagement all stress coral reefs and associated ecosystems such as mangrove and sea grass habitats.
It is also increasingly apparent that impacts from climate change—in the form of higher sea surface temperatures, increased erosion from changed ocean chemistry, more powerful storms, and sea level rise— will bring repeated shocks to coral reefs in the coming years and decades ahead. The outlook for reefs is not good, unless we can halt the degradation, and quickly. A recently published paper in the journal Science suggests that levels of CO2 could become unsustainable for reefs within 50 years, dooming reefs worldwide2. Thus the outlook for reefs is poor -- unless we can halt the degradation, and quickly.
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