Eight of the ten rivers, that carry almost 95 percent of all the plastic debris into the Seas, are from Asia. Ganges and Indus are among them. A recent scientific study has this shocking revelation to make.
Researchers from the Helmholtz-Centre for Environmental Research – UFZ of Germany have found that the mismanaged plastic wastes generated in the river catchments are finding their way to the seas. The debris of plastic waste that they studied included both micro plastic (particles less than 5 mm) and macro plastic (particles more than5 mm). In this global study of plastic wastes across a wide range of river sizes, analysis of data by the researchers found that large rivers with population-rich catchments are responsible for delivering a disproportionately higher fraction of mismanaged plastic wastes into the sea.
The study concluded that the 10 top-ranked rivers transport 88–95 percent of the global load into the sea, and eight of them are in Asia. The rest two are from Africa. (See Box: Ten Rivers, 95% plastic pollution)
Small Box: Ten Rivers, 95% plastic pollution
Yangtze, East China Sea, Asia
Indus, Arabian Sea, Asia
Yellow River, Yellow Sea, Asia
Hai He, Yellow Sea, Asia
Nile, Mediterranean, Africa
Ganges, Bay of Bengal, Asia
Pearl River, South China Sea, Asia
Amur, Sea of Okhotsk, Asia
Niger, Gulf of Guinea, Africa
Mekong, South China Sea, Asia
The study, that analysed data from 79 sampling sites along 57 rivers, found that 5 trillion pounds of plastic is floating in the seas. It claimed that targeting the most polluted rivers could halve the plastic burden of all the seas, even though that might not end the harm that micro plastic is already doing to marine life.
An earlier study by researchers at the Ocean Cleanup, a Dutch foundation, found that rivers carry an estimated 1.15-2.41 million tonnes of plastic into the sea every year. To transport this amount of plastic, we would require between 48,000 to over 100,000 dump trucks, claimed the study. This study, that found that this plastic load is carried to the sea by 20 most polluted rivers of the world, also confirmed that most of them are from Asia. According to the report of the study, published in Nature Communications, the researchers concluded that the top 20 polluting rivers were mostly located in Asia and accounted for more than two thirds (67%) of the global annual input while covering 2.2 percent of the continental surface area and representing 21 percent of the global population. Furthermore, the top 122 polluting rivers (4% of total landmass surface area and 36% of global population) contributed for less than 90 percent of the plastic inputs with 103 rivers located in Asia, eight in Africa, eight in South and Central America, and one in Europe.
This study further claimed that the plastic releases from Asian rivers accounted for almost 86 percent of total global inputs, and almost agreed to what the current study by Helmholtz-Centre has to say about the population density of large basins contributing to large volumes of plastic pollution. In fact, the Ocean Cleanup study methodology also considers rainfall as a major determinant of carrying heavy loads of plastic wastes by the rivers to the seas. It claims that a considerably high-population density combined with relatively large mismanaged plastic waste production rates and episodes of heavy rainfalls, resulted in this dominant contribution from the Asian continent. The rivers of Asian continent were estimated to be carrying a plastic waste load between 1 to 2.06 million tonnes per year into the sea. According to their study, the Chinese Yangtze River is the largest contributing catchment, with an annual input between 0.31 and 0.48 million tonnes of plastic discharged into the East China Sea, followed by the Ganges River catchment, between India and Bangladesh, with a computed input between 0.10 and 0.17 million tonnes per year discharged into the Bay of Bengal.
Plastic in sea to outnumber fish by 2050!
A January 2016 report, prepared by a team from Ellen MacArthur Foundation and published by World Economic Forum, finds that at the current rate of plastic pollution – 150 million tonnes – in the sea, it could outnumber (by weight) the production of fish by 2050. This report points out that each year, at least 8 million tonnes of plastics leak into the ocean – which is equivalent to dumping the contents of one garbage truck into the ocean every minute. If no action is taken, this is expected to increase to two per minute by 2030 and four per minute by 2050. Most of this plastic comes from single use packaging materials that generate significant negative externalities, estimated at 40 billion US dollar and expected to grow significantly. The oceans, as per the estimates of this report, are expected to contain 1 tonne of plastic for every 3 tonnes of fish by 2025, and by 2050, more plastics than fish (by weight).
Sinking carbon sink
Plastic overtaking the sea is a complex problem and has many disastrous effects. The oceans are considered to be the largest carbon sink in the globe as the algae, vegetation and coral under the seas absorb almost 20-35 percent of the carbon dioxide we emit. Things are however changing fast and Oceans are losing their capability to absorb these climate change drivers. A study by researchers at Columbia University published in the Nature in 2009 found that oceans have absorbed a smaller proportion of fossil-fuel emissions, nearly 10 percent less, since 2000. Reporting on that study, the Worldwatch Institute wrote, “Industrial carbon dioxide emissions have increased dramatically since the 1950s, and oceans have until recently been able to absorb the greater amounts of emissions. Sometime after 2000, however, the rise in emissions and the oceans’ carbon uptake decoupled. Oceans continue to absorb more carbon, but the pace appears to have slowed”.
To understand how plastic pollution of the marine ecosystem affects the oceans’ ability to absorb carbon dioxide, it would be good to take the example of Phytoplankton that plays a crucial role in sequestering carbon dioxide from the Earth’s atmosphere and releasing oxygen into the water, which is part of the process photosynthesis. These one-celled plants use energy from the sun to convert carbon dioxide and nutrients into complex organic compounds, which form new plant material. This process, known as photosynthesis, is how phytoplankton grow, explains the National Geographic. “Half of the world’s oxygen is produced via phytoplankton photosynthesis while the other half is produced by photosynthesis on land by trees and other plants,” reports the One Green Planet.
Another species, whales, are also as critically important as phytoplankton. In fact, phytoplanktonrely on whales to exist as they are fertilized by whale excrement that is responsible for fertilizing phytoplankton. It therefore means, we will have fewer phytoplankton if there are less whales. The less phytoplankton there is, the less zooplankton and fish there are and the less carbon dioxide sequestering that is able to occur — and the worse climate change will become, according to the One Green Planet report.
Plastic pollution of the oceans is considered to be responsible for threatening the existence of a large number – almost 700 or more – marine species. In fact, plastic pollution plays a big role in the rising rate of extinction of many marine species.
Cities must act –
Cities in Asia need to take urgent note of the plastic pollution of the oceans that are largely caused by them. City life has become synonymous with a ‘plastic culture’. However, the plans to curb pollution hardly consider the damages being done to marine ecosystem. We need to integrate ocean pollution in our city development plans and work out river basin management plans with a strategic cooperation model between all cities on our river basins. In fact, we can also have trans-boundary and bay-level collaborations between cities for this. We can’t afford to delay this action any further.