Coastal vistas are beautiful, dramatic, inviting, and easily accessible. As a result, they are people magnets. In 1995 more than 2.2 billion people, 39% of the world's population, lived within 100 kilometers (km) of a coastline. Add to these the millions more who vacation in coastal regions annually. In 1997 more than 18.8 million tourists visited the Caribbean alone.

Coastal ecosystems are also an important food source. In 1997, 64 million metric tons of fish and shellfish were harvested from oceans and inland waters and 29 million metric tons from aquaculture for human consumption. Another 29 million metric tons were processed for animal feed.

In addition to their beauty and their value as a food source, coastal ecosystems serve as a natural filtration system. They maintain marine water quality by filtering pollutants from inland freshwater systems. Coastal ecosystems also store and cycle nutrients and help protect shorelines from erosion and storms. Mangroves, wetlands, and seagrass beds filter or degrade toxic pollutants, absorb nutrient inputs, and help control pathogen populations. Conversion or destruction of these ecosystems disrupts that function, often resulting in hazards such as eutrophication and harmful algal blooms.

How extensive are the world's coastal zones?

Whereas other ecosystems are defined by a set of biologically distinct features, coastal regions are characterized geographically — they are the border between land and sea. One definition of

Natural and Altered Landcover within 100 km of a Coast. (click on image to enlarge)

coastal zones is "the intertidal and subtidal areas above the continental shelf (to a depth of 200 meters) and adjacent land area up to 100 km inland." Thus they encompass a range of ecosystem types, both terrestrial and aquatic. Coral reefs, mangrove forests, tidal wetlands, seagrass beds, barrier islands, estuaries, and peat swamps are just some of many coastal ecosystems. Marine fisheries considered to be a significant part of coastal ecosystems because as much as 95% of all marine fish harvested is caught or reared in coastal zones.

Fishing among the mangroves in Brazil.

One estimate of the total length of coastlines worldwide is 1.6 million km. But this may be decreasing because global warming is causing the sea level to rise and submerge low-lying coastal land areas. Small atoll island nations are particularly at risk of submersion. Coral bleaching, which is also caused by global warming, doesn't immediately affect the extent of the reef, but bleaching results when the microscopic algae that live in the majority of corals' tissues are lost. It is a symbiotic relationship, so if the coral cannot recover the algae, the reef will die and eventually erode.

Like global warming, conversion is also diminishing the extent of coastal regions. Already 19% of coastal areas have been converted to agricultural or urban use.

What are some of the most important goods and services provided by coastal ecosystems?

Goods	Services
Food Fish/shellfish comprised 16.5% of the animal protein humans consumed in 1997; it’s the primary protein source for 1 billion of us.	Employment Fishing and aquaculture yielded 29 million jobs in 1990; tourism provided 2.9 million in 1998 in the Caribbean alone.
Construction materials Sand mined from river beds and lime extracted from coral are used to make concrete and cement.	Biodiversity Marine environments provide habitat for a known 250,000 species; thousands more have yet to be discovered.
Pharmaceuticals Many marine organisms provide antibiotics, anti-inflammatory, anti-tumor, and anticancer agents.	Tourism Coastal zones receive a large share of recreation income. In 1998 tourism generated $28 billion in the Caribbean alone.

Water quality is a vital factor in coastal zones.

Water quality is a vital factor in coastal zones. Water quality in coastal ecosystems affects the ability of those systems to provide food, maintain biodiversity, and sustain tourism. Pollution in coastal regions comes from a variety of sources. Residential populations and tourists are certainly major contributors to coastal pollution, but inland populations also are coastal polluters. Pollutants and solid debris travel along inland waterways and are deposited in coastal waters. In 1997, 2.8 million kilograms of dangerous trash was cleaned from 14,000 km of beach in 75 countries; 62% was plastic debris.

Commercial and recreational traffic from inland waterways and from coastal ports is another important source of pollution. Large-scale oil spills have declined, but oil discharges from land-based sources and regular shipping operations are increasing and account for more than 70% of annual oil discharges into the ocean.

Pathogenic organisms, including viruses, bacteria, protozoa, and parasitic worms, naturally exist in seawater. But stormwater and agriculture runoff, along with insufficiently treated sewage released from septic systems on land and ships, can increase the number of pathogens discharged into coastal waters. This increase can force the closing of recreational beaches and cause disease in plants and aquatic and land animals.

Some industrialized nations have reduced releases of some persistent organic pollutants, but chemical discharges increase as agriculture intensifies to feed growing populations and new synthetic compounds are developed. Nutrient overload in coastal waters is associated with harmful algal blooms (HABs) that can cause six types of food poisoning, some of which are lethal to humans and result in disease or death in marine organisms. There were about 200 HAB incidents in the 1970s, but more than 700 in the 1990s. Since 1991 in the United States alone, costs related to HABs reached nearly $300 million in losses from fish kills, public health problems, and lost revenue from tourism and the sale of seafood.