Healthy oceans are essential to a healthy terrestrial environment. The earth's great sea is the heart of the hydrological cycle - nature's solar-driven water pump. About 430,000 cubic kilometres of water evaporate from the oceans every year. Of this amount, around 110,000 cubic kilometres fall as freshwater precipitation over land, replenishing surface and ground waters and eventually completing the cycle by returning to the sea.

© J.P. Nacivet/Planet Earth Pictures

Population distribution

Human populations have a tremendous impact on the quality of coastal and oceanic environments. A full two-thirds of the world's population - 4 billion people - live within 400 kilometres of a seacoast. Just over half the world's population - around 3.2 billion people - occupy a coastal strip 200 kilometres wide (120 miles), representing only 10 per cent of the earth's land surface. With this population distribution, increasing human numbers and mounting development pressures are taking a grim toll on coastal and near-shore resources.

Of Asia’s total population of 3.8 billion, 60 per cent live within 400 kms of a coast. Roughly 1.5 billion live within 100 kms of the sea. The exceptions are India, Pakistan, and, of course, the land-locked countries of Central Asia. The population of Latin America and the Caribbean is even more clustered on the coasts. The region's coastal states have a total population of around 510 million (in 2001); a full three-quarters of them live within 200 kilometres of a coast.

Among continents, only in Africa do more people live in the interior than along or near ocean coasts. But even in Africa demographic patterns are shifting. Over the past two decades, for example, Africa's coastal cities, as centres of trade and commerce, have been growing in population by 4 per cent or more a year, as they attract people from the countryside. Cities such as Lagos, Mombassa, Dar es Salaam, Accra, Abidjan, and Dakar have seen their populations expand greatly from in-migration and local population growth.

Threatened resources

Over half of the world's coastlines have suffered from severe development pressures, according to a study by the World Resources Institute (WRI) in the mid-1990s. The WRI study used four key indicators to assess risk to coastal areas: cities and population density, major ports, road density, and pipeline density. According to these indicators, the coastlines of most developed countries - particularly Japan, Australia, the United States, Europe and the European part of Russia, were suffering from development pressures and loss of coastal resources. But developing countries fared little better - around virtually all urban areas, coasts were beset by a pattern of pollution and over-development.

Coastal wetlands. The world has lost half its coastal wetlands, including mangrove swamps and salt marshes. Over the past century mangrove forests have been decimated - 25 million hectares are estimated to have been destroyed or grossly degraded. In the Philippines, for instance, the mangrove area has been annihilated by development, dropping by 90 per cent - from one million hectares in 1960 to around 100,000 in 1998.

Mangrove wetlands provide a rich habitat for over 2,000 species of fish, shellfish, invertebrates and plants. Some 80 species of salt tolerant trees currently occupy about 182,000 square kilometres of intertidal, lagoonal and riverine flatlands throughout the world.

Seagrass beds, the underwater meadows of the ocean, have fared little better. Though no overall quantitative estimates of damage are available, these diverse ecosystems appear in retreat near virtually all inhabited coastal areas.

Coral reefs. Coral reefs, the rainforests of the sea, are also being destroyed in the name of development. Of the world's 600,000 square kilometres of reefs found in tropical and semi-tropical seas, scientists estimate that 70 per cent of them - some 400,000 square kilometres - could be lost within 40 years.

Soldier fish in coral reef, French Polynesia
© WWF/Y.Lefevre/Bios

Coral reefs are wonders of biological diversity, supporting upwards of one million species and providing humankind with many benefits. They buffer waves and protect shorelines from erosion; they help transfer nutrients from the land to the open ocean; they provide feeding, breeding and nursery areas for many commercially important species of fish and shellfish; and they offer scientists a pharmacopoeia of potential medicines. Yet, they are fast disappearing.

In 1997, a global effort to assess the status of coral resources was carried out by Reef Check, organized by Hong Kong University. The study used professional and recreational divers to chart the health of 300 reefs in 30 countries. According to the survey, less than one-third of all reefs had healthy, living coral cover, while two-thirds were seriously degraded. The Caribbean had the lowest rate of living coral, an average of just 22 per cent. Southeast Asia was second, with only 30 per cent of its coral reefs in good to excellent condition; coral reefs in good to excellent condition must have 50 per cent or more of their area in living coral.

Another study by WRI confirmed these findings, observing that the world's most degraded reefs are in Southeast Asia and the Caribbean. In Southeast Asia, for example, one of the epicenters of coral biodiversity, more than 80 per cent of all reefs are at risk. In 2001 the Worldwatch Institute reported that over the decade of the 1990s, the percentage of the world's coral reefs suffering from severe damage increased from 10 per cent of the total to nearly 30 per cent.

The sea worst hit is the Caribbean. According to a team of British researchers from the University of East Anglia four-fifths of the coral on Caribbean reefs has disappeared in the past 25 years, a phenomenal rate of destruction. Their report, published in Science Magazine in 2003, cites over-fishing, rampant coastal development and pollution as the main reasons for the wholesale annihilation of reef ecosystems.

Coastal erosion. Human activities are eroding close to 70 per cent of the world's beaches at greater than natural rates. Coastlines in developing countries are suffering from serious erosion problems due to unplanned coastal construction, dredging, mining for sand, harvesting of coral reefs for building material and other activities. Erosion is particularly severe along the coasts of Nigeria, Sierra Leone, Liberia, Gambia, Benin and Togo in West Africa. Hundreds of coastal villages have been moved inland as the sea advances. In the Niger River Delta, for instance, erosion claims 400 hectares of land a year and 40 per cent of the inhabited delta could be lost in three decades.

Collapsing fisheries

Coastal and ocean fisheries - the largest harvest of a wild food source on the planet - are in serious trouble. Commercial fishing fleets landed around 84 million metric tons of seafood in 1999, according to FAO. However, this is 9 per cent drop over the banner years of 1996 and 1997 when fleets landed over 86 million metric tons. Commercial fleets landed 92 million tons of fish, shellfish and marine plants in 2001, according to the UN Food and Agriculture Organization (FAO). This is an increase over 1999, when the world’s fleets hauled in 84 million tons. Most stocks remain fully exploited or over-exploited. FAO reports that 47 per cent of the world’s commercial fish stocks are fully exploited, 18 per cent are over-exploited, 9 per cent are depleted and 1 per cent are slowly recovering. Only one-quarter of stocks are considered under-exploited or moderately exploited.

Of the world's 15 major fishing regions, productivity has fallen over the past few years in all but four. Landings of the most valuable species of fish, including cod, tuna, and haddock, have dropped by one-quarter since 1970. In the four hardest hit regions - the northwest, the west-central and the southeast Atlantic, and the east-central Pacific - catches have plummeted by more than 30 per cent since 1989.

In the Black Sea over the 30-year period 1960-1990 the number of commercially valuable fish species plunged from 26 to 5. Catches of commercial fish fell from 1 million metric tons in 1982 to around 100,000 metric tons in 1992. In many areas the sea no longer has any exploitable marine life. The Black Sea is well on its way to becoming a "dead" sea in terms of biological diversity due to pollution spilled over the past four decades (see "Ocean Pollution," below). All waters below 150-200 meters are without oxygen, and only 10 per cent of the total volume of near-surface water has enough oxygen to sustain life higher than micro-organisms.

In Southeast Asia nearly all waters within 15 kilometres of land are considered over-fished, according to Ed Gomez, Director of the Marine Science Institute of the University of the Philippines in Metro Manila. Trawlers, the strip miners of the sea, often precipitate the collapse of fish stocks from years of over-harvesting. But it is small-scale fishers and their families who often pay the price and are forced to use illegal and destructive fishing gear, such as poisons, dynamite and fine mesh nets to put food on the table.

Disappearance of the world's marine catch of fish and shellfish has ominous implications for the food supply of the nearly 1 billion people who depend largely on the sea for sustenance. Seafood provides close to 20 per cent of the world's total food supply. In Southeast Asia and the South Pacific, the sea provides up to 100 per cent of all animal protein in daily diets.

The world's fishing fleets discard at least 20 million metric tons of fish and shellfish every year as by-catch from their operations. Most of the waste is due to trawlers which harvest enormous quantities of marine life in their relentless search for squid, shrimp or bottom dwelling fish (such as halibut, sole or flounder). This loss of potential protein (and income) amounts to one-quarter of the world's annual take from the seas. Losses from discards in the Bering Sea and Gulf of Alaska alone have been estimated at around $250 million a year.

Can aquaculture substitute for the declining ocean fish catch? The answer is uncertain. In 2001, FAO reported that 46 million tons of fish, shellfish and seaweeds were farmed (both marine and freshwater), representing a steady increase since 1994 when 21 million tons were farmed. China accounts for the largest share of farmed marine and freshwater species, with 71 per cent of the total volume and close to 50 per cent of the total value. Aquaculture and mariculture are now worth about $61 billion a year, compared to the value of capture fisheries, which in 2001 was estimated at $81 billion.

Experts worry that aquaculture production, if left to develop unregulated, will end up destroying coastal wetlands and mangrove swamps necessary as breeding and nursery areas for wild stocks and also the source of fry for aquaculture operations. Furthermore, since much of the production from aquaculture and mariculture is exported, this source of food does not contribute to the diets of local people and is viewed by some as a “protein drain from South to North”.

Ocean pollution

Rapidly expanding populations and the growth of cities along coastlines has contributed to a rising tide of pollution in nearly all of the world's seas. Between 80 per cent and 90 per cent of all commercial fish are caught within 320 kilometres of land, and many within 50 kilometres. Thus pollution, mostly from land-based sources, is a contributing factor in falling catches.

Litter on beach, Venezuela
© WWF/Y.Lefevre/Bios

Coastal urban areas dump increasing loads of toxic wastes into the sea. In fact, waters around many coastal cities have turned into virtual cesspools, so thick with pollution that virtually no marine life can survive. Consider the following:

• Despite over two decades of cleanup efforts, the Mediterranean Sea is on the receiving end of between 30 and 50 million metric tons of untreated or partially treated sewage every year;
  
• The Lagoon of Iddo in Lagos, Nigeria, gets 60 million litres of raw sewage a year, along with vast quantities of industrial waste;
  
• Calcutta and Bombay, India, respectively, dump 400 million metric tons and 365 million metric tons of raw sewage and other municipal wastes into coastal waters every year;
  
• Karachi, Pakistan's largest city, empties 175 million metric tons of untreated sewage and industrial filth into the Arabian Sea every year;
  
• Chinese cities and towns along the Yellow Sea discharge 50-60 million metric tons of untreated or partially treated municipal wastes every day into coastal waters;
  
• The Bays of Valparaiso and Concepcion, Chile receive a combined total of 244 million metric tons of untreated effluents a year, mostly from copper mines, pulp and paper mills, fish processing plants and oil refineries;
  
• In 2004, researchers identified 146 “dead zones” around the world’s coastlines, areas where the dissolved oxygen levels are so low that no marine life can be sustained. Moreover, these biologically dead areas are expanding due mainly to high nutrient pollution levels brought in by rivers and streams and washed off coastal land. Since the 1960s, the number of dead zones has doubled every decade. The dead zone in the Gulf of Mexico, now the world’s second largest, covers 21,000 square kilometers, an area the size of New Jersey. The world’s largest dead zone is in the Baltic Sea, covering some 70,000 square kilometers of seabed.

Sustainable use

Coastal and ocean areas can be managed sustainably for the benefit of current and future generations, but only if concerted efforts can be made by national governments and the international community, acting together and working toward a common set of objectives.

Offshore oil platform, Texas
© Denis-Huot/WWF/BIOS

Why is management of coastal and ocean resources so difficult? Coastal areas contain many different jurisdictions - local, regional and national - and involve different interests. In Brazil, for instance, coastal zone planners have to consult 20 levels of government. In the United Kingdom, 48 sub-national units of government, from Parliament to town councils, have authority to create an autonomous or semi-autonomous coastal management strategy. Such fragmentation of responsibility makes effective planning and programme coordination an enormous challenge.

Nevertheless, there are compelling economic reasons to manage coastal and ocean waters better. Ocean ecosystems provide goods and services worth at least $21 trillion a year, over half of this from coastal ecosystems. The haul of seafood alone is valued at over $80 billion a year (as of 2001) and provides direct employment to some 200 million small-scale and commercial fishers. In addition, as many as half a billion people draw their livelihoods indirectly from the sea: processors, packers, shippers, and distributors of seafood; shipbuilders and outfitters; and those working in marine-based tourism and the recreational fishing industry, among others.

There are also vital reasons relating to the ecological value of oceans. For example, coral reefs have been valued at $47,000 per square foot just for their shore protection functions alone. In Puget Sound, Washington, just one-third of a hectare of eelgrass is valued at over $400,000 annually in energy derived and nutrition generated for oyster culture, fisheries, and waterfowl.

A blueprint. How can we manage coastal and ocean resources better? The blueprint for a sustainable management system has been outlined by the World Wide Fund for Nature (WWF) and the World Conservation Union (IUCN) in 1998. The WWF/IUCN approach calls for a six-part strategy, as follows:

• All measures and practices to conserve marine biodiversity and ecological processes must take human needs into account;
  
• The concept of stewardship must be fostered through education and awareness creation;
  
• Communities must be empowered to protect and manage their marine and coastal resources;
  
• Social and economic incentives for conservation and sustainable use must be created;
  
• The inter-connectedness of the world ocean must be recognised through appropriate transboundary and international mechanisms;
  
• The precautionary principle must be applied to an ecosystem-based approach to management.

A number of encouraging initiatives have been launched, but most are difficult to enforce. Two stand out: The FAO Code of Conduct for Responsible Fisheries and the UN Agreement on Straddling Fish Stocks and Highly Migratory Fish Stocks, both launched in 1995. The Code of Conduct was adopted by 170 nations, but did not come into force until April 2002. As of January 2004, 30 nations had ratified it, including the US and the EU. The UN Agreement on Fish Stocks entered into force in December 2001, when Malta ratified it, bringing the total number of ratifications to 30.

In the final analysis, governments must take the lead in managing their own waters, cooperating as much as possible with neighbouring states through UN programmes such as the Regional Seas initiatives of UNEP and other international bodies. It is not too late to start preserving the ultimate source of all life on the "blue planet".

This overview is written by Don Hinrichsen, a Contributing Editor to peopleandplanet.net and author of Coastal Waters of the World, Island Press, Washington DC, $60 hb.

© People & the Planet 2000 - 2007