Sections

Services

Information

UK United Kingdom

Leave the ocean garbage alone: we need to stop polluting first

Recent plans to clean plastics from the five massive ocean garbage patches could do more damage to the environment than leaving the plastic right where it is. There is no doubt that the focus on cleaning…

Great ocean garbage patches should be left alone until plastics are stopped from entering our oceans. Flickr/CesarHarada

Recent plans to clean plastics from the five massive ocean garbage patches could do more damage to the environment than leaving the plastic right where it is.

There is no doubt that the focus on cleaning up those garbage patches is admirable. They are a disgrace. Each is hundreds to thousands of kilometres across and together they are one of the most obvious signs of just how much we as humanity are polluting our oceans.

Boyan Slat is a young aerospace engineer who has been working on a plan to filter out plastics from the patches. It is a wonderfully original approach to this problem that is certain to have broader applications well beyond the plastic in garbage patches.

However, we need to reconsider a knee-jerk response that involves rushing to fish out all the plastic. That’s because of the way the ocean circulation has created the gyres where garbage patches form. When all things are considered, there are perhaps few places in the world where floating plastics could do less harm.

The real harm caused by plastic in our oceans lies much closer to home. And the ocean currents tell us why.

Ocean deserts

One of the more interesting aspects of the centres of the ocean gyres where the patches form, is that they are the ocean equivalent of deserts. There is very little life there. It is the reason why there are hardly any commercial fisheries in these areas and why it is perhaps one of the safest places for these plastics to remain.

It is because this area is an ocean desert that we can say (often in a dramatic voice) that if you were to put a net in the water in one of these gyre centres, you would pull up more plastic than ocean life.

I admit to being guilty of using this statement. However, while it is certainly true that there is a lot of plastic in the gyres, it is also true that there is very little ocean life in these same places, so the bar for this statement is set rather low.

The reason for this lack of life is because the water is nutrient poor. And the reason why the water in the gyres is nutrient poor is the exact same reason why the garbage patches form there.

Follow the nutrient trail

The first important thing to understand is that surface water in the ocean doesn’t stay at the surface forever. Ocean currents move water both horizontally from one ocean region to another, as well as vertically between the surface and the deep ocean.

In some areas, mostly along coastlines, at the Equator and in the Southern Ocean, there is upwelling of nutrient-rich water from the deep ocean. In other areas, primarily in the centre of the gyres, there is downwelling, where nutrient-poor surface water gets pushed back to the deep ocean.

The time taken for a particle of water to move from the upwelling regions near the coasts to the downwelling regions in the centre of a gyre can often be measured in decades. During these years of moving from coast to gyre, surface-dwelling plankton consume the nutrients.

So, the older age of the water in the regions of downwelling means that there are hardly any nutrients left in the water to sustain life once it reaches the patches. Without nutrients there are far fewer plankton.

The lack of plankton caused by this loss of nutrients makes it difficult to sustain a marine food web, which also means that there are comparatively little fisheries going on in the patches. Most of global fisheries actually happen where nutrient rich “new” water comes to the surface.

The garbage patches also form in the old-water gyres because plastics are too buoyant to descend with this downward current. They stay behind on the surface and collect in the ocean garbage patches, exactly where most water downwells.

Preventing plastic from getting in the ocean

By focusing on this far-from-shore clean up we are missing the more pertinent concern. The real and direct impact of ocean-going plastic is not where it ends up, but the route it takes from our beaches to the garbage patches.

It’s when the plastic passes through these ecologically and economically important regions that we should be most concerned. These are the places where we fish.

We have recently shown that it can take up to 50 years for plastic released from our shorelines to travel to the patches. That means that even if we would clean up the garbage patches today, the garbage would return within a few decades, as the plastic that is currently spread across the ocean slowly accumulates again.

If we stop polluting today, within a few decades there will be almost no more plastics in our oceans outside of the garbage patches.

Only then, once we have stopped plastics entering our oceans in the first place, can we sensibly make the decision whether and how we want to spend the resources to clean the distant garbage patches.

Join the conversation

12 Comments sorted by

  1. Rotha Jago

    concerned citizen

    Thanks for this article. It highlights the need for changing our ways on land rather than bravely attempting to clean the ocean.
    We live on the coast in Far North Queensland. During our frequent walks on the beach we notice that the reef lagoon is changing and not for the better.
    Ten years ago the plastic debris on the beach drew everyone's attention.
    Now, at first glance there seems to be much less plastic. On closer inspection
    the plastic is in tiny pieces. This implies to me that it has been…

    Read more
    1. Jon Brodie

      Research scientist

      In reply to Rotha Jago

      The smaller pieces of plastic you now see may also be just the broken down pieces of the original plastic. Most plastic is degradable by UV light and temperature and breaks into very small pieces. Note this is NOT biodegradation. A good example is the 'environmentally friendly shopping bags' - coloured apparently woven stuff. If you look closely this is made out of polypropylene and NOT biodegradable. If you leave them out in the sun and rain in north Queensland they just disintegrate into small…

      Read more
    2. Rotha Jago

      concerned citizen

      In reply to Jon Brodie

      I have not seen the 2nd report, I would like to see it. I read the first Reef protection Plan and watched the video with horror and dismay.
      A farmer near Tully, the wettest area in Australia was taking sediment, washed into drains by heavy rains, and after removing topsoil from his field, was placing the sediment mud on the field and then replacing the topsoil. This was, he explained all paid for by a Commonwealth Government Grant, to save the Reef.
      All this unnecessary work would not have needed to be done if he had refrained from spraying his drains with herbicide.
      In Tully field drains, grass grows quickly, and grass is the best and cheapest way of filtering water and retaining topsoil.
      These 'new' ways of 'protecting the Reef' are a disgraceful waste of money. And worse still they do not save anything except the bottom line of Monsanto or Syngentia or whoever is selling the Herbicide.

      report
    3. Greg North

      Retired Engineer

      In reply to Jon Brodie

      Some of those bags even disintegrate even if undercover outdoors out of the sun and rain.

      report
  2. Wade Macdonald

    Technician

    We need to address both facets, land and ocean. Put the super trawlers to work and get rid of this plastic. What this plastic is doing to our planet once broken down is of great concern.

    report
    1. Suzy Gneist

      Multiple: self-employed, employed, student, mother, volunteer, Free-flyer

      In reply to Wade Macdonald

      yet, what to do with it all once we collect it? burn it? bury it? recycle it? ...and still we create more of the stuff every day.

      report
    2. James Hill

      Industrial Designer

      In reply to Suzy Gneist

      Yes, a plan to turn the plastic into diesel (yes it pollutes the air) was viable only if the fuel excise applied to diesel was waived in the case of this recyling industry.
      John Howard refused.
      Plastics remain as waste.

      report
    3. Rotha Jago

      concerned citizen

      In reply to James Hill

      Can it be converted to diesel? All or only some plastics?
      In Canada, where roads are made over permafrost, I heard they use plastic bags to make a resilient road base. I've often wondered if that technology could be used in coastal areas in Queensland, where road makers have to build roads to cope with intermittent flooding.

      report
    4. Yoron Hamber

      Thinking

      In reply to Rotha Jago

      I think they mix it in some types of concrete too, here in Sweden, but it's been some time since I heard that one. But you do get different qualities out of it, mixing.

      report
  3. Alex Cannara

    logged in via Facebook

    Very good, common-sensical thinking.

    report
  4. Zvyozdochka

    logged in via Twitter

    Having sailed across these areas of ocean, people's impression of what the 'garbage patch' is are completely wrong. There are not huge clumps of plastic floating in a concentrated mass. It is dispersed, but more concentrated in the gyre area. We're talking thousands of square kms. As usual, an engineering response by "filtering it" sounds great, but I can't imagine how it will be achieved.

    Birds are suffering terribly however - urgent action is required at the source.

    How about, like the SA container deposit, a packaging deposit that ALL manufacturers have to honour? By a twin pack of biros with more packaging than the pen at the supermarket, BIC have to pay you 10c when the packaging is returned.

    report