The water planet: earth is the only planet that we know about with such an abundance of water; nature provides humanity with an incredibly valuable resource in the world's oceans.

Robert Costanza is a different kind of economist. He and his colleagues call themselves "ecological economists." They factor in the value of Nature when calculating the worth of goods, production, and national wealth.

In 1997, Dr. Costanza and others created a bit of a stir when they published an article in the science journal Nature in which they estimated the annual value of the biosphere to be $33 trillion U.S. This figure is greater than all the annual Gross Domestic Product of the world's economies combined.

The ecological economists estimated the value of the oceans to be $21 trillion, while the land was worth $12 trillion. The actual figures are debatable; only bestguess estimates. The really interesting aspect is that the oceans were given almost twice the value of the land.

That shouldn't be surprising; 71 percent of the planet is covered by water. But, when all is said and done, it is just water. However, the world's oceans are far more than that. They are:

* The basic source for the hydrologic cycle that makes life on Earth possible;

* A global thermostat that regulates entire climates;

* The cleaning agent that absorbs carbon dioxide and generates oxygen;

* A primary source of animal protein (fish) for one billion people;

* The superhighway that carries most globalized trade; and,

* The playground for tens of millions.

There are some more specific numbers that go along with those assets.

The oceans are Nature's solar-driven water pump. About 430,000 cubic kilometres of water evaporate from the oceans every year. Of this, around 110,000 cubic kilometres fall on Earth's land surface as precipitation. That's a lot of water; the flow over Niagara Falls is one cubic kilometre every 46.27 hours. This water makes the growing of crops possible. The run-off then refills lakes and rivers before flowing back to the ocean to refuel the hydrologic cycle.

The ocean is also the engine that drives the world's climate. Water absorbs and holds vast amounts of solar energy, which is then released slowly. This has the effect of changing climates almost everywhere by moderating extremes of heat and cold.

Oceans absorb and store carbon dioxide from the atmosphere. Because this invisible gas is one of the main agents of climate change, the ocean is an important sink that helps to modify human impacts on global climate.

In 2004, scientists put numbers on the absorption of carbon dioxide. Worldwide tests suggest that the oceans have taken up 48 percent of all carbon dioxide emitted from fossil fuel burning between 1800 and 1994. That adds up to about 120 billion tonnes of greenhouse gasses taken out of circulation, halving the current level of global warming.

Tiny plants called phytoplankton feed on the C[O.sub.2] and sunlight. The by-product of this phytoplankton growth is oxygen. Scientists estimate the oceans are the source for about half the planet's oxygen.

Fishing employs about 200 million people worldwide. In addition, as many as half a billion other 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. Capture fisheries gather up about 90 million tonnes of fish a year, worth somewhere in the region of $80 billion U.S. Aquaculture is growing at a rapid rate as a source of seafood and is approaching a third of the world's supply of fish.

Offshore oil and gas is now a huge and growing industry. Over the last two decades, underwater oil production has gone up by 37 percent and that of gas has risen by 27 percent. The world now gets 30 percent of its oil and half its natural gas from wells drilled in the ocean floor. New technology and more discoveries mean that undersea oil and gas production will continue to rise.

And, then there are the world's beaches. The World Travel and Tourism Council estimates the value of tourism worldwide in 2003 to have been $3.5 trillion U.S. The Council does not say how much of this is associated with beaches, but it's got to be a very hefty chunk.

Some research in California in 1997 found that just that one U.S. state's beaches generated $27 billion of economic activity in 1995. Residents and tourists together made more than 565 million visits to California's beaches.

SUGGESTED ACTIVITY:

Canada has the longest coastline of any nation in the world and borders three oceans. Through map study find out if there are any other countries that have coasts on three oceans.

HOW DEEP IS THE OCEAN?

When Irving Berlin wrote the lyrics to How Deep the Ocean, in 1932, the answer wasnt known. Today, we know; it varies.

Where the land meets the water is the continental shelf; the floor goes down to about 150 metres below the surface. At the edge of the continental shelves is a cliff that plunges to the ocean floor's average depth of between three and five kilometres.

Far out in the middle of the oceans, there is a belt of higher floor called the "mid-oceanic ridge." This is an underwater mountain range rising from the ocean floor by two to three kilometres. The summits of the highest underwater peaks are still a couple of thousand metres below the ocean surface.

The deepest parts of the ocean are deep-sea trenches. These are generally off the continental shelves and plunge as much as 11 kilometres. The deepest point is 11,033 metres below the surface in the Mariana Trench in the Pacific Ocean.

Only in recent years, have we developed technologies that will get us to the deepest parts of the oceans and back again alive. Not surprisingly, not much is known about what happens down there. What is known is bizarre.

On the deep ocean floor scientists have found hydrothermal vents. From these vents a toxic brew of superheated water, hydrogen sulphide gas, and heavy metals bubbles forth. The pressure at these depths would crush a human as flat as a sheet of paper, and there is no light.

In this harshest of environments several hundred life forms exist, about 95 percent of them unknown until the 1980s. There are tubeworms, blind shrimp, and giant white crabs. These unique animals seem to find poisonous chemicals yummy enough to survive on through a process called chemosynthesis.

A COASTAL SPECIES

Already nearly two-thirds of humanity--some four billion people--crowd along a coastline, or live within 150 kilometres of one. Within three decades, if trends continue, 75 percent of humanity, or 6.4 billion people, will reside in coastal areas. Everybody wants to squeeze onto this strip that represents less than I0 percent of Earth's land area.

In the United States, 54 percent of all Americans now live in 772 coastal counties adjacent to the Atlantic and Pacific Oceans, the Gulf of Mexico, and the Great Lakes.

Of China's 1.2 billion people, more than 677 million (56 percent) live in 13 southeast and coastal provinces and two coastal cities--Shanghai and Tianjin. Along much of China's 18,000 kilometres of continental coastline, population densities average more 600 per square kilometre; in Shanghai, they exceed 2,000 per square kilometre. Coastal regions are where almost all of China's future growth is expected to be.

In much of the rest of the developing world, coastal cities are exploding. In Southeast Asia, 65 percent of all major cities--those with populations of 2.5 million or more, are located along coasts. In Latin America and the Caribbean, 57 out of 77 major cities are coastal.

One of the most over-crowded coastlines in the world is the Mediterranean. The current population of the Mediterranean Basin countries is around 380 million, with 146 million living along the coast itself. Another 100 million tourists flock to its shores every summer. By 2025, the Med could be hosting up to 350 million tourists a year.

FACT FILE

Earth's largest geological feature is a continuous, underwater mountain range that snakes for 50,000 kilometres through the Atlantic, Pacific, Indian, and Arctic Oceans.

Websites

International Society for Ecological Economics--http://www.ecoeco.org/

National Oceanic and Atmospheric Administration (U.S.)--http:// www.noaa.gov/index.html

Voyage to the Deep--http:// www.ocean.udel.edu/ deepsea/