Issues in Interdisciplinarity 2020-21/Evidence in The Plastic Continent

Introduction
The Plastic continent also known as the eighth continent lies between California and Hawaii and is three times the size of France. It is made of 1,8 billions pieces of floating plastic greatly impacting the marine life. This is one of the biggest issues in environmental science and climate change. Evidence about this continent is brought by different fields as it is an interdisciplinary issue. We will see how scientific and sociological methods can conflict with each other on this issue.

Measurement
Due to its waterborne nature, measuring the plastic continent and determining its location has proved a difficult task. A variety of approaches have been used to estimate these properties, producing a wide range of results. Estimates of the area it covers range from the size of Texas to the size of Russia.

The existence of the patch was first theorised by a study researching the distribution of plastic in a patch in the Japan sea which extrapolated that a similar patch must exist in the pacific with a much higher density of plastic. This was based on analysis of wind and ocean current patterns.

There are studies which have surveyed plastic distribution on beaches because this is much easier than surveying the sea, although many factors such as current and beach structure affect this as well as plastic from beach users, so it is an unreliable method for inference about oceanic plastic distribution.

Trawling surveys at sea are more direct but due to the size of the ocean it is difficult to gather enough data for a reliable result.

Image surveys conducted using aircraft were able to assess much larger areas giving more reliable information but could only account for plastic larger than 50cm so were no use in analysing microplastics. Scientist have also monitored the wildlife near the patch. One study onː The plastic content in the diet of albatrosses from Pacific islands showed that there were two distinct zones of debris.

Evidence in Chemistry
Plastic is all over in our everyday life. Unfortunately, it is almost indestructible (a single plastic bag can take up to 1000 years to degrade) and really hard to recycle.

Toxic chemicals are released in the ocean from the decomposition of the plastic as hydrophobic organic pollutants. « Microplastics behave like little chemical sponges and all of these very toxic, persistent substances that are in the water will stick to the outside of the plastic in order to move from the aqueous environment to a more hydrophobic environment » according to Sherri Mason, environmental chemist. Those microplastics help to move those chemical products of the environment to organisms that ingest them. Those chemicals come from the chemical composition of the plastic produced by industrial companies. They contain chemical additives such as plasticisers, colorants or UV stabilisers. Evidence of this chemical pollution due to microplastics can be seen in the organisms of marine animals and birds that eat them thinking it is their natural food. Once they are ingested those microplastics can desorb and then are stored in the fat of those animals. Chemicals can affect the ability of marine organisms to store energy and therefore animals have a lower life expectancy.

Evidence in Biology
The food chain is disturbed by microplastics in the ocean. Turtles are found entangled in plastic bags or birds’ stomachs are found to be full of plastics. Dissections by biologists of hundreds of those species found dead near beaches or in the droppings of animals pointed out this excessive amount of microplastics. According to Greenpeace, around 1,5 million animals are victims of this plastic pollution in the oceans each year. Those ingestions of plastic have consequences on the health of those marine species such as inflammatory cellular responses or other diseases as necrosis, birth defects, cancers, effects on immune system due to alteration of gene expression... Those effects have been shown mostly through research conducted on dolphins.

Evidence of this plastic continent is also seen in the studies and researches into sediments. Depending on the weight of microplastics some sink and lead to a great amount of plastic on the sea floor. The investigation of plastic in the deep sea is difficult due to limited access. However, some have detected in samples microplastics from depths up to five kilometres with a new extraction technique using high density salt solutions to float the plastic and separate them from other solids.

Evidence in Economics
Plastic has been mass produced and is difficult to destroy so plastic waste is a big issue which economists have created models to explain.

Considering that international legislations forbid direct littering at sea, it is difficult for Economists to measure Plastic waste into the Ocean. However, light products usually make their way into the sea passing through rivers or helped by the wind. Therefore, to calculate Plastic in the Ocean, Economists decide to calculate inadequately managed waste in order to measure the amount of plastic but also the countries that pollute the most. They created an equation: ‘Inadequately managed plastic wastes = Plastic waste per capita x Inadequately managed waste % x population’ and it delivers results proving that in a Capitalist Economy like ours with growing GDP per capita, Plastic waste especially in the ocean is a growing problem. Moreover, these calculations are based on ‘very conservative estimates’, and the actual amount of Plastic waste is far greater than the one they used for the calculations.

Political Evidence
In addition to assessing the waste management of different countries, studies have used qualitative methods to determine debris' origin. One study reported a rapid increase in Asian bottles. Computer models of ocean currents have been used to predict the course plastic debris would follow and then from this determine its origin. All studies around this matter are liable to political bias.

The actual Laws
The territorial waters and the subsoil and airspace above and under it are up to 12 nautical miles away from the cost, the country which borders them has the right over these waters. The Exclusive Economic Zone (EEZ) is a maximum width of 200 miles beyond the baselines. In the EEZ, the coastal State has a sovereign right for the purposes of exploration and exploitation, conservation and management of natural resources, the seabed and their sub-surface. The State can for e.g. regulate fishing activities. Beyond the EEZ, in the high seas, the States no longer have rights. In these Seas, the concept of freedom governs. The only right that States have is the right of hot pursuit in High Seas if it began in the EEZ of the coastal State. Because the Plastic Continent is in the high Seas, no country could be sued for not taking care of it

Conclusion
The long-term impacts of oceanic plastic are unknown so extrapolation is necessary to assess its danger. It is waterborne so researching it causes technical challenges. Its dynamic nature means it is difficult to quantify and trace. There are many different methods of gathering evidence on it and the conflicting results they produce make it clear that an interdisciplinary approach is necessary to reach a consensus.

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