It's great that the ocean has a day all of its very own, of course, and even better that the United Nations has given the day its official imprimatur. But there's a case to be made that, frankly, every day should be ocean day. After all, Earth is the only planet known to have liquid water on its surface and the only planet known to have life. These facts are not coincidental.
Not only did life on Earth began in the ocean; more than 3.5 billion years later, the ocean and atmosphere are engaged in an interplay that continues to make continued life on Earth possible. The ocean is the engine that drives our planet's climate systems: without it, Earth would be intolerably hot during the day and frozen at night.
Pretty good reason, all by itself, to be thankful for the ocean, right? In celebration of its one officially-recognized day, here are some other blow-your-mind nuggets about the magnificence of the ocean realm:
We all know that the ocean covers approximately 71 percent of the surface of the planet (more than 80 percent in the Southern hemisphere). But it also constitutes over 90 percent of the habitable space on Earth, because whereas on land, almost all life clings to the surface, in the ocean it is found from top to bottom, from the sunny surface to the cold, dark depths.
How much water is in the ocean? About 260 million trillion gallons. Which, for the record, is enough to fill roughly 20 million trillion bathtubs.
There is approximately 220,000 miles of coastline in the world, almost enough to reach from Earth to the Moon. More than half of that coastline is in Canada, which has almost four times as much as the runner-up, Indonesia. In contrast, tiny Monaco has just 2.5 miles of coast.
But the most numerous lifeforms in the ocean are microbes - which, if added together, would weigh more than 200 billion African elephants. There are so many marine viruses in the ocean that, if stretched end to end, they would reach farther than the nearest 60 galaxies! Just one drop of seawater may contain as many as 350,000 microbial lifeforms, which means there are many, many more of them in the sea than there are stars in the entire Universe.
Thanks to the efforts of the Census of Marine Life, the estimated number of known marine species presently stands at around 250,000. However, a 2011 study suggested that the ocean may contain 2.2 million species - which means roughly 90 percent remain undiscovered.
Many marine species travel great distances across the ocean. The largest migrations of any mammal on Earth are undertaken by humpback whales that swim from Antarctica to the waters off Costa Rica - a journey of almost 5,000 miles. But even the mighty humpbacks must take a bow in the direction of the bar-tailed godwit, which flaps its wings furiously as it flies from the coast of Alaska to New Zealand without once pausing for food.
Humans have been taking advantage of the ocean's bounty for a long, long time. There is evidence of early humans in southern Africa taking shellfish as far back as 164,000 years ago. People may have been hunting tuna off the coast of Australia 42,000 years ago.
Today, 41 percent of the world's population lives within 62 miles of the coast. Fish accounts for approximately 15 percent of the world’s animal protein; it provides more than 1.5 billion people with almost 20 percent of their average per capita intake of such protein.
According to the United Nations Food and Agriculture Organization, there are roughly 4 million fishing vessels in the world, from the largest industrial trawlers to small boats powered by sails and oars; between them, they catch over 140 million tonnes of fish a year.
But our fondness for the ocean and the life it contains has come at great cost. For example, a 2011 study estimated that 28-33 percent of all fish stocks are over-exploited, and that 7-13 percent have collapsed.
April 18, 2013, Plaquemines Parish, Louisiana, Cat island in Barataria Bay three years after the BP oil spill is now barren. Before the spill it was vibrant bird rookery for pelicans egrets and roast spoon bills. BP oil washed up on the shore killing birds and then over time killing the mangrove trees and marsh grass leaving the island vulnerable to coastal erosion, a process already jeopardizing the island and other barrier islands protecting the Gulf Coast.
Coastal marine habitats also are feeling the pressure. Since 1980, an area of seagrass meadow the size of a soccer field has disappeared every 30 minutes - or one-third of the time it takes to complete a game of soccer. Globally, about 35 percent of mangrove forests have disappeared in the same time frame, while 34 percent of the world’s coral reefs have already been destroyed or are in imminent danger of collapse, with a further 20 percent at risk of loss within 20-40 years.
The ocean may be vast, but it is not indestructible. As famed scientist James Lovelock has observed, “Although the weight of the oceans is 250 times that of the atmosphere, it is only one part in 4,000 of the weight of the Earth.” If the Earth were a globe 12 inches in diameter, Lovelock noted, the average depth of the ocean would be no more than the thickness of a piece of paper, and even the deepest ocean trench would be a dent of a third of a millimeter.
So, bear that in mind - on World Oceans Day, and every day - when you consider what fish to eat, whether or not to buy that plastic bottle of water, and whether to throw away your trash or recycle it.
Happy World Oceans Day, and remember this famous quote from science fiction writer Arthur C. Clarke: "How inappropriate to call this planet Earth, when clearly it is Ocean."