Angelo Young

24/7 Wall Street

About 70% of the Earth’s surface is covered by oceans. Not only were they the womb from which life likely emerged at least 3.5 billion years ago, but they act as the planet’s thermostat, transferring heat from the tropics to higher latitudes and absorbing a substantial amount of the carbon dioxide that the world’s plant life does not convert into oxygen through photosynthesis.

Changes to the ocean chemistry, currents, and temperatures have profound effects on global weather patterns, and human industrial and consumption activity is adversely impacting the oceans and their complex ecosystems. The result is a number of species are being driven to extinction.

Plastic pollution has received much attention in recent years as people cringe at images of tropical beaches covered in plastic bags and bottles, animal deaths caused by plastic, and the massive garbage patches found in all of the world’s largest bodies of water. This increased focus has helped raise awareness of ocean pollution.

But plastic pollution is just one of the issues. A major and often ignored threat to the oceans’ health is greenhouse gas emissions, especially excessive carbon dioxide, which humans are releasing into the atmosphere. These emissions are not only linked to global warming, but also they are causing ocean acidification that is wreaking havoc on marine ecosystems.

In addition to carbon emissions and plastics pollution, oceans are also polluted from oil and chemicals that wash into rivers and wind up in the oceans. This type of pollution, called nonpoint source pollution, includes oil leaked from cars and trucks and runoff from farms and ranches that send herbicides, pesticides, and fertilizers into the oceans via rainwater runoff into rivers.

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Taking all three of these major sources of ocean pollution into consideration, 24/7 Wall St. compiled a list of the 20 companies behind among the largest amount of oceanic pollution, including major producers of single-use plastic containers, fossil fuel companies, meat and dairy producers, and agricultural chemical manufacturers responsible for the largest share of oceanic contamination.

It is important to note that this list is not meant to be a conclusive ranking of the world's top polluters. However, these 20 companies represent our best estimate of the largest polluters in the world, based on their relative size in industries that are known to pollute heavily, as well as estimates of these companies' greenhouse gas emissions by third parties.

Energy Corporations

Saudi Aramco

When burned, fossil fuels emit greenhouse gases, which cause ocean acidification, a harmful process that disrupts marine ecosystems. The state-owned Saudi oil and gas giant is the world's most profitable company. It is also the biggest emitter of greenhouse gases in the fossil fuel sector, according to CDP. In addition to being the industry leader in GHG emissions from its own operations, Saudi Aramco is the overall leading supplier of fossil fuels in the global energy sector.

Gazprom

The state-owned gas giant and Russia's most valuable publicly traded company is the second largest source of greenhouse gases, which causes ocean acidification, among global fossil fuel companies based on 2015 data. It ranks third among the top energy companies in terms of greenhouse gas emissions from operations, but the burning of the petroleum liquids and natural gas it produces and sells puts it in second place in overall greenhouse gas emissions, after Saudi Aramco.

National Iranian Oil

National Iranian Oil ranks second in greenhouse gas emissions from its operations and third in total emissions linked to its operations and its products behind Saudi Aramco and Gazprom. Recent U.S. sanctions may have impacted the company's ranking, but Iran's state-owned oil and gas company remains one of the top producers and suppliers of greenhouse gases.

Coal India

India's state-owned coal company is the world's single largest generator of coal-based pollution, slightly ahead of China's Shenhua Group based on 2015 data. It is also the fourth largest producer of greenhouse gases among fossil fuel companies. As the dirtiest source of energy, coal burning contributes to ocean acidification.

Shenhua Group

China's state-owned largest coal company was slightly behind its Indian counterpart, Coal India, in total greenhouse gas emissions. The company ranks fourth in greenhouse gas production among the world's top fossil fuel companies and. Overall, China's coal industry is by far the world's biggest source of greenhouse gas production and supply – responsible for more than 14% of human-sourced greenhouse gas emissions between 1988 and 2015, according to CDP.

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Plastic Products Corporations

Coca-Cola Company

The Atlanta-based beverage behemoth is the top producer of plastic rubbish making its way into the world oceans, wreaking havoc on wildlife and sending plastic particles into the food chain, according to a global sampling last year of trash Greenpeace and Break Free From Plastic collected in 42 countries around the world. The world's leading beverage bottler, which markets hundreds of brands of carbonated beverages, water, and juices, said last year it uses 3 million tons of plastic packaging annually.

PepsiCo

A global sample of garbage collected on ocean shores and waters last year by Greenpeace and Break Free From Plastic organizations found that the North Carolina-based snack and beverage giant was second to Coca-Cola as the leading source of plastic garbage in the world's oceans. Plastic packaging can take hundreds of years to decompose, and in the oceans it breaks down into tiny pieces that enter the food chain and kill wildlife that consumes it.

Nestlé

The Swiss multinational food and beverage company, whose brands include Gerber baby food, Perrier water, and KitKat chocolate among others, is the third largest source of plastic trash found in the oceans, according to a global sample of garbage collected on ocean shores last year by Greenpeace and Break Free From Plastic organizations. The company disclosed this year that it uses 1.7 million tons of plastic annually to produce its plastic packaging.

Danone

The French multinational food and beverage company, whose brands include Activia and Evian, is the fourth largest source of plastic garbage in the world's oceans. Danone disclosed last year that it uses about 750,000 tons of plastic annually to package its products. Plastic is the most common trash found in the oceans and it wreaks havoc on marine ecosystems.

Mondelez International

A global sample of ocean garbage collected last year found that the Illinois-based confectionary, food, and beverage company is the fifth most common source of plastic marine trash. Unlike other major plastic garbage producers on this list, the maker of Oreo cookies and Cadbury chocolate did not participate in recent U.N. program urging packaging producers to disclose the amount of plastic they use and to commit to more environmentally friendly practices in the future.

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Agrochemical Companies

Bayer

Following its acquisition of seed maker Monsanto last year, the German multinational pharmaceutical and chemical company became the world's largest supplier of seeds and agricultural chemicals. These chemicals are a key source of nonpoint water pollution. Like the oil that leaks from vehicles, pesticides like the ones produced by Bayer wind up in rivers that carry agricultural runoff into the oceans.

Syngenta

The Switzerland-based, Chinese-owned agrochemical and seeds producer was the world's largest by sales in 2017 before Bayer took first position following its acquisition of Monsanto last year. As the second largest agrochemical and seeds producer, Syngenta is one of the largest suppliers of herbicides and pesticides used in agricultural activity. These chemicals wash into rivers that carry them into coastal ecosystems.

BASF

The largest chemical company in the world by revenue is also a leading producer of agricultural pesticides, herbicides, and fertilizers. The German multinational company ranked third in agrochemical sales in 2017. Many of these chemicals wind up in the ocean through nonpoint water pollution, meaning there is no single specific source of contamination.

Corteva

DowDuPont finalized on June 3 the separation of its agricultural business unit into a standalone company, Corteva Agrisciences. The move comes after the completion of a merger between Michigan-based The Dow Chemical Company and Delaware's E.I. du Pont de Nemours in 2017. The merger made DowDuPont the fourth largest seller of agrochemicals, the segment now under the Corteva name. Herbicides, pesticides ,and fertilizers pollute ocean water from rainwater runoff that makes its way to rivers, tributaries, and coastal wetlands.

ADAMA

The Israel-based, Chinese-owned company is a leading producer of agricultural chemicals and the world's largest producer of generic pesticides. It was acquired by China National Chemical Group in 2011. ChemChina later bought Syngenta, putting two major agrochemical producers under one parent company. Herbicides, pesticides, and fertilizers pollute oceans through rainwater runoff into rivers.

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Meat and Dairy Corporations

JBS

The Brazilian multinational company is both the world's largest meat processor and the biggest single emitter of greenhouse gases in the global food industry, according to the Institute for Agriculture and Trade Policy and the international nonprofit GRAIN. The seller of meat, chicken, and pork products is responsible for more GHG emissions than the other top three leading meat and dairy companies combined. Carbon dioxide, the primary greenhouse gas, makes ocean water more acidic, which then causes great harm to marine ecosystems.

Tyson Foods

Arkansas-based Tyson is the second largest meat processor and the second biggest emitter of greenhouse gases in the global food industry, making it, according to the Institute for Agriculture and Trade Policy, one of the largest single sources of greenhouse gas emissions on the planet, when the energy used to produce animal feed and the agricultural chemicals used to grow it are considered. The primary greenhouse gas, carbon dioxide, makes seawater more acidic and harmful to ecosystems.

Cargill

The Minnesota-based, privately held conglomerate is heavily involved in the production of livestock and grains for livestock nutrition. Cargill's operations are not limited to meat and poultry as the company's diverse businesses include agriculture products, food and beverages, beauty products and more. The company ranks as the third biggest source of greenhouse gas emissions in the global livestock industry, according to a report last year by the Institute for Agriculture and Trade Policy and the international nonprofit GRAIN.

Dairy Farmers of America

The Kansas-based milk marketing cooperative is the fourth biggest source of greenhouse gas emissions in the meat and dairy industry if its livestock feed and agrochemicals operations are included. Much of the carbon dioxide from meat and dairy production winds up in the oceans, which makes them more acidic and harmful to sea life.

Fonterra

New Zealand commands an enormous share of the market in global whole milk powder, and much of that is under the control of Fonterra. The company is the fifth largest source of GHG emissions when the energy used to produce feedstock is included.

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Methodology

To determine the corporations behind the most ocean pollution, 24/7 Wall St. reviewed information about the different sources of pollution: plastic pollution; runoff from agricultural pesticides, herbicides, and fertilizers; and greenhouse gas emissions.

For the primary company sources of plastics pollution, we used a 2018 study of plastic garbage collected in 42 countries and catalogued by Greenpeace and the Break Free From Plastics movement. For the primary sources of greenhouse gases – oil, gas, and coal companies responsible for the most greenhouse-gas emissions – we reviewed data from 2017's Carbon Majors Database from the Carbon Disclosure Project (CDP), a UK-base charity encouraging carbon emissions reporting. The database considered data from 2015. A 2018 report from the international nonprofit organization GRAIN and the Institute for Agriculture and Trade Policy (IATP), a non-profit focused on environmental sustainability, provided the largest meat and dairy companies that release the most greenhouse gas emissions. We used a 2018 report from Agrow, an agribusiness intelligence company, to find the biggest producers of agricultural chemicals based on sales, which is how we determined the largest polluters in the industry.

The U.S. National Oceanic and Atmospheric Administration provided background on so-called nonpoint source pollution, the ocean pollution that comes from runoff from vehicular oil leaks, farms, and ranches.

24/7 Wall Street is a USA TODAY content partner offering financial news and commentary. Its content is produced independently of USA TODAY.