In A Harsh Reality I wrote about the Green Revolution and its effects on food production. In this article I’d like to focus your attention on our ocean fisheries.
World fisheries are in a state of collapse – caught between plagues of jellyfish, overfishing, nutrient pollution, bioaccumulation of toxics in marine mammals, carbon emissions turning our oceans acidic, the oceans phytoplankton declining by about 40 per cent over the past century, dead zones, garbage patch’s, increasing ocean temperatures and changing currents - our entire marine food chain seems to be in peril.
Populations of jellyfish are exploding around the globe. They feed on the same kinds of prey as fish so if fish numbers are depleted jellyfish fill the gap.
Overfishing isn't the only explanation for exploding jellyfish populations.
An ocean dead zone is an area of the ocean that’s hypoxic, which means that it has low oxygen. The reasons for ocean dead zones are most commonly attributed to toxic chemicals and human waste (eutrophication - high levels of nutrients), infiltrating the water near coastlines. The low oxygen levels created favor jellyfish as they can thrive in oxygen depleted water whereas fish can’t.
Oceanographers first began noticing ocean dead zones in the 1970s, and instances of dead zones have been increasing ever since - a tenfold global increase over the last 40 years. Large lakes can also have dead zones.
Phytoplankton are microscopic single cell plant organisms and are the most abundant vegetation in the ocean - they drift in the ocean currents and occupy most of the surface area of the earth's oceans. They are the first, the bottom link, in the oceanic food chain - they are the crucial nutrient at the base of the food chain on which all marine life depends.
They are eaten by zooplankton (microscopic animal organisms) which are eaten by other animals, which are then consumed by other animals higher up the food chain.
Temperatures on the surface of our oceans are rising - the result is a reduction in the numbers of phytoplankton. Since 1950, phytoplankton numbers have declined globally by about 40 percent. Experts are already warning us that because of overfishing the world's fisheries could collapse by 2050 - the decline in phytoplankton could make the situation even worse.
Half of the oxygen produced by plants comes from phytoplankton. They are vital in maintaining the earth’s atmosphere and the oxygen we need to survive. For a long time there has been an extremely small, but constant, decline in the oxygen content of our atmosphere. It's possible that the loss of phytoplankton could be a factor. Phytoplankton also absorb a huge amount of carbon dioxide each year.
Ocean acidification is the name given to the ongoing decrease in the pH of the Earth's oceans. CO2 dissolving in seawater increases the hydrogen ion concentration in the ocean, thus decreasing ocean pH. Between 1751 and 1994 the ocean surface pH is estimated to have decreased from approximately 8.25 to 8.14 - an acidity increase of roughly 30%.
“Ocean acidification only really came to the fore about five years ago…As acidity and sea temperature increase, the ocean’s ability to absorb atmospheric CO2 will be reduced…this could trigger a chain reaction that reverberates throughout the marine food web … starting with vulnerable species such as larval fish and shell fish, and ending with detrimental effects to the global fishing industry and the food security of many of the world’s poorest people.” Professor Dan Laffoley, co-editor ‘Ocean Acidification: The Facts’
About 6.4 million tons of marine litter are disposed of in the oceans and seas each year - some eight million items of marine litter are dumped in oceans and seas every day - up to 80 per cent of marine garbage is thought to come from land-based sources. 2005 United Nations Environmental Program Report The Pacific, the Atlantic and Indian Ocean “Garbage Patch’s” formed as a result of marine pollution gathered by oceanic currents.
Tiny pieces of trash, each less than a tenth the weight of a paper clip, make up most of the debris. In some places the Atlantic Ocean Garbage Patch contained more than 200,000 bits of trash per square kilometer.
The Great Pacific Garbage Patch was found to have as many as 750,000 bits of plastic per square kilometer. If that’s not bad enough waves often carry the plastic as much as 20 meters below the surface.
The powerful ocean current system creates a flow of warm surface water, the Gulf Stream, from the Caribbean northwards. A branch of the Gulf Stream, the North Atlantic Drift, transports warm water into the north Atlantic. As it travels to the Arctic the warm water heats the countries of the North Atlantic. As the water gets further and further north it cools, which increases its density. The dense water sinks to the bottom of the ocean where it is carried back to the equator. Think of it, as an on its side, oval racetrack stretching from the Caribbean into the northern Atlantic.
Research has found that the influence of the cold water Labrador Current on the Gulf Stream has been decreasing continually since the 1970s. In May 2005, researchers reported the results of an investigation measuring the giant chimneys of cold dense water by which the water normally sinks down to the sea bed. They found the chimneys have virtually disappeared. Usually there are seven to twelve giant columns, but they found only two giant columns, both extremely weak.
A Gulf Stream shutdown or a slowdown could have major consequences regarding fish stocks:
- A collapse of plankton stocks
- An oceanic anoxic event - oxygen below surface levels of the stagnant oceans becomes depleted
Consider all of the above, then read the rest of the article. You can see where we might run into some trouble regarding global fisheries.
The UN’s Food and Agriculture Organization (FAO) says “The maximum wild capture fishery potential from the world’s oceans has probably been reached.”
FAO scientists publish a two yearly report (SOFIA) on the state of the world's fisheries and aquaculture:
- 53% of fish stocks are fully exploited
- 32% are over exploited, depleted or recovering from depletion
SOFIA 2010 recorded a rise to 85% in the number of fisheries that are fully exploited or over exploited, depleted or recovering from depletion.
Most of the stocks of the top ten species (30 percent of the worlds marine fisheries production in terms of quantity) are fully exploited. The proportion of under or moderately exploited fisheries able to produce higher catches is 15 per cent - the lowest level recorded since the mid 1970s
“In a world likely to face a future of increasing food prices and decreasing food security it is becoming more and more apparent that running down one fishery after another is a disaster in the making.” Alfred Schumm, leader of WWF’s global Smart Fishing Initiative
Industrial fishing has, over the past fifty years, depleted the topmost links in the marine food chain - worldwide about 90% of the stocks of large predatory fish stocks have disappeared. We’ve been “fishing down the food chain” - as the larger fish disappear we go after smaller and smaller fish.
Conclusion
Globally, fish provides more than 1.5 billion people with almost 20 percent of their average per capita intake of animal protein, and 3.0 billion people with at least 15 percent of such protein. UN’s Food and Agriculture Organization (FAO) SOFIA 2010
A United Nations Environment Program (UNEP) report “In Dead Water” published January 2008 said “as much as 80 percent of the world's main fish catch species have now been exploited beyond or close to their harvest capacity.” SOFIA 2010 recorded a rise to 85% in the number of fisheries that are fully exploited or over exploited, depleted or recovering from depletion.
The world's oceans are already a mere shadow of what they once were and fish stocks are still dwindling.
Is our food supply, from land and ocean, on your radar screen?
If not maybe it should be.
