|Reefs at Risk - A Map-Based Indicator of Threats to the World's Coral Reefs (WRI, 1998, 56 pages)|
Coral reefs are among the most valuable ecosystems on earth because of their immense biological wealth and the economic and environmental services they provide to millions of people. According to one estimate, reef habitats provide humans with living resources (such as fish) and services (such as tourism returns and coastal protection) worth about $375 billion each year.4
Coral reefs are important for the following reasons:
Biodiversity: Coral reefs are among the most biologically rich ecosystems on earth About 4,000 species of fish and 800 species of reef-building corals have been described to date.5 However, experts have barely begun to catalog the total number of species found within these habitats. One prominent scientist, Marjorie Reaka-Kudla, estimates there may be between one and nine million species associated with coral reefs.* Using this figure and rough estimates of human-caused reef degradation. Dr. Reaka-Kudla projected that over a million of these species may face extinction within the coming four decades6
* Reaka-Kudla's figures may be high. Scientists who helped prepare the Global Biodiversity Assessment (United Nations Environment Programme, 1992) estimated that there are perhaps 14 million species altogether, counting those within land and aquatic environments. Others suggest even greater diversity is possible, when microbial life is fully considered.
Coral Reef Ecosystems
Coral reefs resemble tropical rainforests in two ways: both thrive under nutrient-poor conditions (where nutrients are largely tied up in living matter), yet support rich communities through incredibly efficient recycling processes. Additionally, both exhibit very high levels of species diversity. Coral reefs and other marine ecosystems, however, contain more varied life forms than do land habitats. All but one of the world's 33 phyla (major kinds of organisms) are found in marine environments - 15 exclusively so.7
Coral reefs are noted for some of the highest levels of total (gross) productivity on earth. Coral polyps - the thin living layer covering reef structures - provide much of the energy that fuels these communities. These tiny animals contain algae, which convert sunlight to fuel, deriving nutrients from polyp wastes in the process. Reef-building corals and certain calcareous algae (which may constitute more than half of a reef's stony substance) lay down a foundation of calcium carbonate. Over generations this accumulation results in often massive structures, providing homes and hiding places for countless other creatures. Coral reefs, then, are the net result of thousands of years of growth. As such, many are among the planet's oldest living communities.
In general, coral reefs are found in shallow waters, between the Tropic of Capricorn and the Tropic of Cancer. Their total extent is unknown, although it probably exceeds 600,000 square kilometers.8 The World Conservation Monitoring Centre recently mapped the global distribution of shallow reefs (the base maps for this study). Using these data, Mark Spalding and A. M. Grenfell estimated the total global area of near-surface reefs (these being the most diverse, productive and economically important reefs) to be some 255,000 square kilometers.9 Coral reefs represent less than 0.2 percent of the total area of oceans (and cover an area equivalent to 4 percent of the world's cropland area).
Levels of species diversity vary within these ecosystems,
depending on location. The most species-rich reefs are found in a swath
extending through Southeast Asia to the Great Barrier Reef, off northeastern
Australia. More than 700 species of corals alone are found in this region.
Within the Great Barrier Reef, 1,500 species of fish and 4,000 species of
mollusks have been counted. Reefs outside this region are important for the
distinct populations and species they contain. For example, although fewer types
of corals are found in the Red Sea, this basin contains more endemics (species
found nowhere else) than other portions of the Eastern Indian Ocean.10,
Reef-associated plants and animals provide people with:
Seafood: Much of the world's poor, most of whom are located within the coastal zones of developing regions, depend directly on reef species for their protein needs. Globally, one-fifth of all animal protein consumed by humans comes from marine environments - an annual catch valued at $50 billion to $100 billion.12 In developing countries, coral reefs contribute about one-quarter of the total fish catch, providing food, according to one estimate, for one billion people in Asia alone.13. 14 If properly managed, reefs can yield, on average, 15 tons of fish and other seafood per square kilometer per year. However, in many areas of the world, fishers are depleting this resource through overexploitation and destructive fishing practices. According to a World Bank estimate, Indonesia forfeits more than $ 10 million a year in lost productivity, coastal protection, and other benefits through large-scale poison fishing alone. Through careful management, these reefs could support a $320 million industry, employing 10,000 Indonesian fishers.15
New medicines: In recent years, human bacterial infections have become increasingly resistant to existing antibiotics. Scientists are turning to the oceans in the search for new cures for these and other diseases. Coral reef species offer particular promise because of the array of chemicals produced by many of these organisms for self-protection. This potential has only barely been explored. Corals are already being used for bone grafts, and chemicals found within several species appear useful for treating viruses. Chemicals within reef-associated species may offer new treatments for leukemia, skin cancer, and other tumors.16 According to one estimate, one-half of all new cancer drug research now focuses on marine organisms.17, l8
Other products: Reef ecosystems yield a host of other economic goods, ranging from corals and shells made into jewelry and tourism curios to live fish and corals used in aquariums, to sand and limestone used by the construction industry. However, such extractive activities are usually damaging to these habitats.
Coral reefs offer a wide range of environmental services, some of which are difficult to quantify, but are of enormous importance to nearby inhabitants. These services include:
Recreational value: The tourism industry is one of the fastest growing sectors of the global economy. Coral reefs are a major draw for snorkelers, scuba divers, recreational fishers, and those seeking vacations in the sun (some of the finest beaches are maintained through the natural erosion of nearby reefs). More than 100 countries stand to benefit from the recreational value provided by their reefs. Florida's reefs pump $1.6 billion into the economy each year from tourism alone.19 Caribbean countries, which attract millions of visitors annually to their beaches and reefs, derive, on average, half of their gross national product from the tourism industry, valued at $8.9 billion in 1990.20
Coastal protection: Coral reefs buffer adjacent shorelines from wave action and the impact of storms. The benefits from this protection are widespread, and range from maintenance of highly productive mangrove fisheries and wetlands to supporting local economies built around ports and harbors, where, as is often the case in the tropics, these are sheltered by nearby reefs.
Globally, we estimate almost half a billion people live within 100 kilometers of a coral reef, benefiting from the production and protection these ecosystems provide (see Figure 1). A recent study found that the costs of destroying just one kilometer of reef range from about $137,000 to almost $1.2 million over a 25-year period, when fishery, tourism, and protection values alone are considered.21