How does it get there?

In the previous post I touched upon just how much waste is in our oceans, to try and illustrate the sheer size of the issue we have on our hands - an issue made up of over 5 trillion pieces, to be a bit more precise. To give some context to the matter it might be useful to explore exactly where it is that all this waste is coming from, as finding the root of the problem is one way of helping kick start the solution to it. The short video below provides a basic conceptualisation of the various journeys that marine debris can take in order to get to the ocean.

Essentially, marine debris comes from us, humans. Some of us leave it lying around on the beach, some of us dump it in an over flowing bin. We may even drop it on the street, miles away from any beach or coastal resort, but if it makes its way into a drainage system it'll almost certainly end up in the sea. This video demonstrates the importance for each and every one of us to act consciously when thinking about how we dispose of everyday waste such as plastic bags and food wrappers. However, one aspect that this video does fail to touch upon is the impact that large companies and organisations have on waste inputs into the sea. 

Some of the prime culprits of marine dumping are fisheries. Studies in the UK have shown that fisheries remain responsible for a large amount of marine waste that is being washed up on our shores - despite international conventions that have been set up to stop exactly that. The International Convention for the Prevention of Pollution from Ships, also known as MARPOL, was adopted in 1973 with the sole purpose of preventing and minimising pollution from ships. However, these studies have shown that in many cases the rules and regulations are simply being ignored. 

Developing countries are also coming under increasing scrutiny with regard to their management, or mismanagement, of plastic waste. Economic growth is strongly associated with an increased per capita consumption of goods, and studies have shown that this is creating a volume of waste that many developing countries do not have the infrastructure to deal with. This is ultimately leading to uncontrolled or open landfill sites where waste materials are vulnerable to being blown away into the ocean. A map of the top contributing countries according to this trend is shown in Figure 1 below.

Figure 1: Top 10 countries for mismanaged waste (CNN, adapted from Science 2010)

Figure 2 below nicely sums up the relative contributions to ocean waste from some of the various sources discussed. It may be evident that fisheries pose a problem regarding the dumping of waste in our oceans, and developing countries absolutely need to find a way to better manage their storage of waste. However, the pie chart proves there is no doubt that we the people need to act more responsibly when throwing away our waste.

Figure 2: Sources of marine waste in 2009 (Ocean Conservancy 2012)

As was alluded to in my opening post, plastic marine waste is not the only pollutant of our oceans. Chemical waste also poses a huge threat to the condition of our seas. Sewage systems are one of the methods of transportation whereby chemicals that are a threat to the ocean's ecosystems can make their way into the sea. Once there, these substances can lead to the reduction of oxygen levels and cause decay of submarine plant life. Industries are also often responsible for dumping toxic chemicals directly into rivers which eventually lead to the ocean. As well as being deadly to marine life due to the toxins contained in these chemicals, the temperature of them when dumped can also cause what is known as thermal pollution, whereby organisms die as a result of the heat. 

Then there is also the problem of pesticides. Designed to be lethal to particular organisms, farmers can use them to significant effect in trying to achieve larger crop yields. However, they can also be lethal to other organisms when they eventually make their way into the sea. Predominantly, this occurs as surface water runoff. When rain water runs off the ground surface it takes the pesticides with it when it enters streams and rivers, and you guessed it, these eventually wind their way into the ocean. A small amount can also enter rivers and streams as a result of 'spray drift'. This is when the pesticide being sprayed is carried to the water bodies directly by the wind, though this process is not thought to make as significant a contribution as the runoff component does.

So there we have it - that is how marine waste, both physical and chemical, manages to find its way into the ocean. In the upcoming posts we'll be having more of a look at some of the many possible impacts that this waste can have once it is in the sea.