The sandy beaches, rocky shorelines, water, and waves of coastal areas are perhaps most readily associated with recreation and natural beauty. Coastal ecosystems, however, have an economic value beyond their aesthetic benefit, supporting human lives and livelihoods through the provision of food and materials, nutrient cycling, waste processing, and other essential goods and services.

By one estimation, the combined global value of goods and services from coastal ecosystems is over US$12 trillion annually (1997 dollars; Costanza et al., 1997)--a figure larger than the United States' Gross Domestic Product in 2004. Yet many of these services are not explicitly priced in world markets, leaving governments, businesses, and individuals with few incentives to maintain them.

Ecosystem Services and The Relative Contributions of Different Coastal System Subtypes. Larger circles represent a higher relative magnitude.
Source: Millennium Ecosystem Assessment.

Assessing Coastal Ecosystems

The current state of coastal ecosystems was thoroughly documented in the Millennium Ecosystem Assessment (MA), a five-year study involving more than 1,300 experts in 95 countries. The study identified coastal ecosystems as "among the most productive yet highly threatened systems in the world" (MA, Coastal Systems). Population growth and technological advances have fueled an unprecedented and unsustainable exploitation of coastal resources in the past century. The MA revealed dramatic declines in the overall health of many different types of coastal ecosystems: coral reefs, mangroves, and estuaries (all discussed below) as well as marshes, dunes, deltas, seagrass beds, and kelp forests.

Coral Reefs

Despite covering only 0.2% of the sea-floor, coral reefs contain 25% of global marine species. These highly productive ecosystems also provide inland protection from storm surges and are integral to both coastal fisheries and tourism, supporting the livelihoods of approximately 100 million people around the world. According to the Millennium Assessment:

-- 20% of coral reefs have been destroyed in the last few decades and an additional 20% or more are severely degraded, particularly in the Caribbean Sea and parts of Southeast Asia.

-- Revenue from tourism associated with coral reefs has been estimated to be US$30 billion annually; reef-based tourism generates over US$1.2 billion each year in the Florida Keys (U.S.) alone.

Mangroves

Coastal mangroves--trees that live in saline intertidal zones--currently cover an estimated 18 million hectares, one-quarter of the world's tropical coastline. Mangroves supply local communities with timber and fuel, provide habitats for commercially-important fish and crustaceans, remove heavy metals from water sources, and control erosion along coastlines. According to the Millennium Assessment:

-- An estimated 35% of mangroves have been removed due to shrimp and fish aquaculture, deforestation, and freshwater diversion. Although some successful restoration efforts have taken place, these are not keeping pace with mangrove destruction.

-- Intact mangrove forests typically have a significantly greater economic value than areas cleared for other uses, even if the value of these ecosystem goods and services is not captured in current economic models. A study in Thailand estimated the value of services provided by intact mangroves to be nearly US$4000 per hectare, significantly greater than land converted for shrimp farming.

Estuaries

Estuaries are areas where freshwater river outflow reaches the oceans. Over 1,200 major estuaries currently exist, comprising an area of roughly 500,000 square kilometers and accounting for 80% of the world's freshwater discharge. Estuaries serve as natural filters of water pollution, critical nurseries for many important commercial fish species, and habitats for a host of unique animals and plants. According to the Millennium Assessment:

-- More than one-half of original estuarine and wetland areas have been substantially altered in the United States alone. For example, intensive nutrient runoff from agriculture has created an oxygen-depleted "dead zone" in the Gulf of Mexico.

-- The benefits of estuaries are not always captured by conventional economics. Muthurajawela Marsh, a 3,100-hectare coastal peat bog in Sri Lanka, provides an estimated US$5 million in annual benefits through its role in local flood control.

Expansion of Shrimp Farming in the Gulf of Fonseca.
Bright blue areas (right photo) are shrimp ponds.
Length of solid white bar = 5km.

Fonseca, Honduras, 1987 (left) and 1999 (right)

Source: UNEP, 2005. One Planet Many People: Atlas of our changing environment.

The Human Impact

Roughly 40% of the world's population--2.6 billion people--live within 100 kilometers of the coast, exacerbating both the scale of global destruction and the need to protect these systems for human well-being. Human proximity to coastal ecosystems leads to both direct and indirect impacts:

• Pollution and excessive nutrient loading (eutrophication);
• Invasive species;
• Overfishing and destructive fishing and tourism practices;
• Coastal development, land degradation from agriculture, habitat loss, and altered sedimentation patterns; and
• Climate change.

In isolation, some of these drivers may not ultimately degrade an entire ecosystem, but their cumulative effects can be severe.

Case Study: Caribbean Coral Reefs

According to the Reefs at Risk Index, overfishing, coastal development, pollution, and sedimentation have seriously degraded nearly two-thirds of coral reefs in the Caribbean region. In addition to these direct threats from human activities, corals are particularly vulnerable to the effects of global warming. Rising levels of carbon dioxide in the atmosphere cause increases in ocean acidity, which hinders reef growth by degrading the calcium carbonate skeletons of corals. Because corals thrive within a narrow range of temperatures, even minimal ocean warming can stress coral reefs, causing them to expel their symbiotic algae, or "bleach." A 2005 bleaching event and disease outbreak in the Caribbean affected 70% of all reefs and caused widespread coral mortality. The presence of multiple stresses greatly reduces the likelihood of reef recovery. Some estimates project that, if unregulated, the compound effects of human-related stresses will cause coral reefs to nearly disappear by mid-century.

Click image to access high-resolution version of this map.

Investing for the Future

With hundreds of millions of people reliant the goods and services from coastal ecosystems, it is critical that greater care be taken with coastal resources. Without them, many people will be placed at a higher risk of food insecurity, exposure to natural disasters, reduced health, and rising sea levels.

Coastal ecosystems will ultimately benefit from improved awareness and education, better monitoring systems, and increased efforts to reduce the effects of both global stresses (e.g., international action on climate change) and individual practices (e.g., reducing personal seafood consumption). Together, these initiatives can help establish a framework for the long-term management of coastal ecosystems, balancing profits with preservation.

RELATED LINKS:

EarthTrends

Reducing Pollution, Destructive Fishing Practices Will Help Coral Reefs Cope With Climate Change

Why are wetlands important ecosystems?

Sewage and Pollution Rapidly Degrading Coastal Ecosystems

Coral Reefs: Assessing the Threat

Other Publications

Marine and Coastal Ecosystems and Human Well-being:

A synthesis report based on the findings of the Millennium Ecosystem Assessment (pdf)

Ecosystem Challenges and Business Implications (pdf)

RELATED WRI PUBLICATIONS

Watershed Analysis for the Mesoamerican Reef (forthcoming)

Reefs at Risk in the Caribbean

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