Plastic in world oceans: A growing problem
Mar 21 2013
In an open ocean, currents and wind combine to form massive, swirling vortexes called gyres. The North Pacific Subtropical Gyre is one of five major gyres on earth and stretches between the coasts of Japan and California. In this area, a combination of high atmospheric pressure and the earth’s rotation slows the ocean currents and moves them in a clockwise spiral. Historically, the Northern Pacific Gyre (NPG) has created a rich concentration of plankton and other organisms; recently, however, the gyre has become home to plastic waste drawn from all over the world, particularly from Pacific Rim countries. The result is two enormous masses of plastic trash. One, dubbed the Western Garbage Patch, is located west of Hawaii and east of Japan. The second is the Eastern Garbage Patch, located near the Northwestern Hawaiian Islands. Together, these masses are known as the Great Pacific Garbage Patch (the “Patch”). Ocean currents carry plastic trash to the Patch from all over the world, and debris that ends up in territories of the US may have originated thousands of miles away.
The Patch is characterised by exceptionally high concentrations of pelagic plastics, chemical sludge and other debris that have been trapped by the currents of the North Pacific Gyre. The size of the patch is unknown, as large items readily visible from a boat deck are uncommon. Most debris consists of small plastic particles suspended at or just below the surface, making it impossible to detect by aircraft or satellite. Instead, the size of the patch is determined by sampling. Estimates of size range from 700,000 square kilometres to more than 15,000,000 square kilometres (0.41 per cent to 8.1 per cent of the size of the Pacific Ocean), or, in some media reports, up to “twice the size of the continental US.”
A curious question to ask is how much of the world plastic reaches the oceans and how much gets to the Patch? Different sources inform us that since its production in the 1950’s, plastic production has increased from 5 million tonnes per year in 1955 to close to 225 million tonnes per year in 2009. Adding all this plastic over the last 60 years and assuming that very little of it would actually biodegrade, yields about 5,050 million tonnes of plastic produced in the world since its discovery and widespread use. As per Greenpeace, of the 5,050 million tonnes of plastics, 505 million tonnes (10 per cent) ends-up in the oceans. Further, of the 505 million tonnes, 152 million tonnes (30 per cent) floats on or just below the surface, and 353 million tonnes (the remaining 70 per cent) sinks to the bottom of ocean floor.
As per derived estimates, this great increase in the number of plastic fragments in the Patch affects at least 267 species worldwide, including 86 per cent of all sea turtle species, 44 per cent of all seabird species, and 43 per cent of all marine mammal species. In the Patch, it is reported that nearly half of the albatross chicks hatched every year die. A study by the environmental protection agency (EPA) found that the chicks that died from starvation or dehydration had twice as much plastic in their stomachs compared to chicks, which died for other reasons. The effects of adsorption of toxic chemicals like PCB, DDE and DDT on small sized plastics or “nurdles” (less than 5 mm in size) and subsequent poisoning in animals is currently less known and needs more research.
Considering the scale of the problem what can we do about it? The amount of plastic in the world oceans including the Patch is enormous to be cleaned up by the budget of a single country. Also, the problem of plastic is largely unaddressed by the law both in different world nations as well as at the international level. Thus, there is an urgent need to formulate a new international treaty that involves different nations in a cleanup of the plastic in the world oceans. This treaty should consider the plastic problem as a global problem where resources of different developed and developing nations could be pooled together. But without plugging the source of the plastic from the land to the oceans each year, the ocean plastic cleanup might be less than a partial solution to the whole problem. Thus, in addition to cleaning the plastic that already exists in world oceans, there is an urgent need to give impetus to land-based cleanup methods like recycling as well as development of standards that promote better handling and transport of nurdles from place of manufacture to place of use. In addition to these steps, there is a need for we as individuals to inculcate better habits of disposing plastic waste in efficient ways (which includes putting recyclable plastic bottles in separate bins separate from rest of trash). These steps when taken, would definitely help to solve the world plastic problem and restore earth and oceans back to their native states.
(The writer is on the faculty of Indian Institute of Technology, Mandi, India)