Keep in mind that climate change is a constant — so constant that it doesn't need discussion here — but we do need to discuss global warming.  There is plenty of evidence that the world is experiencing a warming trend.  It has in the past, and temperatures will likely fluctuate again and again in the future.  The big question is whether man-made greenhouse gasses are the major culprit in causing the current trend.  Are we putting enough carbon dioxide into the atmosphere to cause the entire planet and its oceans to get warmer?  The answer may surprise you.

As hard as it is to believe, we are very likely the culprits, but not in the way the media and governments believe.  You see, overfishing the world's oceans and destroying the balance of this largest of ecosystems may actually be a greater cause than our fossil fuel use.

The oceans, which cover 70% of the planet, take up significant amounts of the world's CO2 and may be the largest carbon sink on the planet.  This is because the largest and most complex ecosystem on the planet is in the water.  It is an ecosystem that humans have devastated and will likely destroy in the 21st century, all things remaining the same.

So far, oceans have absorbed about 90% of the excess heat believed to be caused by human fossil fuel emissions, and they have taken up about 25% of global manmade CO2.  But the oceans follow a carbon cycle that at times absorbs carbon, and at other times releases carbon.  This cycle is influenced dramatically by the living ecosystem in the water.

The ocean takes up carbon dioxide through photosynthesis of the plant-like organisms called phytoplankton, which also rely on ocean turbulence to feed on small minerals.  This carbon dioxide ultimately ends up stored in undersea sediments deep in the ocean.  This is called "the biological pump," and it takes up more than 99% of the planet's carbon.

There are about 1.5 billion tons of fish biomass in the ocean as well, and bony fish participate in the total absorption of carbon by the ocean by ingesting carbon dioxide, which is transformed into calcium carbonate.  Their wastes contain magnesium, which causes the mineral to dissolve more readily and reduce the acidity of the warmer water, and allows it to contain more oxygen.  They also appear to be ingesting higher levels of CO2 as the amount increases in the atmosphere.

Carbon enters the ocean by chemical reaction, too.  For example, carbon dioxide reacts with salt water and creates carbonic acid, which in turn releases hydrogen ions.  These ions combine with carbonate in saltwater and create bicarbonate, which does not readily leave the ocean.

Unfortunately, this enormous system is seriously endangered by overfishing and the destruction of the seafloor by reckless fishing techniques.  According to National Geographic, "[a] study of catch data published in 2006 in the journal Science grimly predicted that if fishing rates continue apace, all the world's fisheries will have collapsed by the year 2048."

Across the planet, 90% of the large predatory fish, like sharks, tuna, and swordfish, are already gone, and almost 80% of the world's known fisheries are fully exploited by industrial fishermen.  These fish populations are over-exploited, depleted, or actually collapsing, and the fishing industry is going into deeper water to get the rest.

The technique of trawling is destroying the animals and plants that keep our oceans alive, too.  This widespread industrial fishing technique involves dragging heavy nets, large metal doors, and chains over the seafloor to catch fish.  According to the USGS, the seabed torn up by bottom-trawling is equal to "all sediment being deposited on the world's continental shelves by rivers each year (almost 22 gigatons)."  Bottom-dwelling plants and animals are destroyed by tearing uproot systems and animal burrows.  "Nutrient levels in the ambient water and the entire chemistry of the water are changed."

The area of ocean floor destroyed by U.S. trawlers alone is over 230,000 square miles, which is larger than the State of California.  Globally, the area is estimated by some to be greater than the size of Australia with a few European countries thrown in.

The answer is pretty clear: we are destroying the oceans by destroying the ecosystem within them.  Some 70% of this ecosystem remains a mystery to us land-dwellers.  There is no mystery as to what we are doing to the oceans, and what that will do to us if we don't immediately begin taking action.  You can cry about plastic straws all you want — they make up about three-tenths of one percent of the plastic in the ocean.  Some 60% of the rest is plastic fishing nets and equipment.

Image: Fishing boats at Bayou La Batre.  Public Domain.