In the Earth’s wheel of life, the oceans provide balance. Covering over 70% of the planet’s surface, they play a critical role in maintaining its life-support systems, in moderating its climate, and in sustaining animals and plants, including minute, oxygen-producing phytoplankton.
They provide protein, transportation, energy, employment, recreation, and other economic, social, and cultural activities. The oceans also provide the ultimate sink for the by-products of human activities.
Huge, closed septic tanks, receive wastes from cities, farms, and industries via sewage outfalls, dumping from barges and ships, coastal run-off, river discharge, and even atmospheric transport. In the last few decades, the growth of the world economy, the burgeoning demand for food and fuel, and accumulating discharges of waste have begun to press against the bountiful limits of the oceans. The oceans are marked by a fundamental unity from which there is no escape.
Interconnected cycles of energy, climate, marine living resources, and human activities more through coastal waters, regional seas, and the closed oceans. The effects of urban, industrial, and agricultural growth are contained within no nation’s Exclusive Economic Zone (EEZ); they pass through currents of water and air from nation to nation, and through complex food chains from species to species, distributing the burdens of development, if not the benefits, to both rich and poor.
Only the high seas outside of national jurisdiction are truly ‘commons’, but fish species, pollution, and other effects of economic development do not respect these legal boundaries. Sound management of the ocean commons will require management of land-based activities as well. Five zones bear on this management: inland areas, which affect the oceans mostly via rivers; coastal lands-swamps, marshes, and so on- close to the sea, where human activities can directly affect the adjacent waters; coastal waters-estuaries, lagoons, and shallow waters generally-where the effects of land-based activities are dominant; offshore waters, out roughly to the edge of the continental shelf; and the high seas, largely beyond the 200-mile EEZs of coastal states’ control. Major fisheries are found mostly in offshore waters, while pollution affecting them comes mostly from inland sources and is concentrated in coastal waters.
Formal international management is essential in the areas beyond the EEZs, although greater international co-operation, including improved frameworks to coordinate national actions, is needed for all areas. Today, the living resources of the sea are under threat from over-exploitation, pollution, and land-based development. Most major familiar fish stocks throughout the waters over the continental shelves, which provide 95% of the world’s fish catch, are now threatened by
overfishing.
Other threats are more concentrated. The effects of pollution and land development are most severe in coastal waters and semi-enclosed seas along the world’s shorelines. The use of coastal areas for settlement, industry, energy facilities, and recreation will accelerate, as will the upstream manipulation of estuarine river systems through dams or diversion for agriculture and municipal water supplies. These pressures have destroyed estuarine habitats as irrevocably as direct dredging, filling, or paving. Shorelines and their resources will suffer ever increasing damage if current, business as usual approaches to policy, management, and institution continue. Certain coastal and offshore waters are especially vulnerable to ecologically insensitive onshore development, to competitive overfishing, and to pollution.
The trends are of special concern in coastal areas where pollution by domestic sewage, industrial wastes, and pesticide and fertilizer run-off may threaten not only human health but also the development of fisheries. Even the high seas are beginning to show some signs of stress from the billions of tons of contaminants added each year. Heavy metals from coal-burning plants and some industrial processes also reach the oceans via the atmosphere. The amount of oil spilt annually from tankers now approaches 1.5 million tons.
There was an average of 1.8 large oil spills from tanker incidents every year in the decade from 2010 to 2019. So far, for 2020, there have been no noted oil spills where more than 700 metric tons of oil was leaked. In the years since the 1970s, the number of oil tanker spills has been notably reduced (Feb 5, 2021). The marine environment, exposed to nuclear radiation from past nuclear weapons tests, is receiving more exposure from the continuing disposal of low-level radioactive wastes.
New evidence of possible rapid depletion of the ozone layer and a consequent increase in ultraviolet radiation poses a threat not only to human health but also to ocean life. Some scientists believe that this radiation could kill sensitive phytoplankton and fish larvae floating near the ocean’s surface, damaging ocean food chains and possibly disrupting planetary support systems. High concentrations of substances such as heavy metals and petroleum have been found on the oceans’ surface. With continued accumulation, these could have complex and long-lasting effects.
The sea floor is a region of complex physical, chemical, and biological activity where microbial processes play a major role, but as yet serious damage is known to have occurred only in very localised regions. Although these findings are encouraging, given accelerating pressures and the inadequacy of present data they provide no grounds for complacency.