Ocean Pollution Worsens and Spreads

At the same time that marine scientists are reporting that the world’s growing appetite for seafood may drive major fish populations to extinction in coming decades, humans are undermining marine health by using the oceans as a dumping ground.1 (See Figure 1.) From inland farms and coastal sewage systems to transoceanic cruises and greenhouse gases, 80 percent of pollutants in oceans originate on land.2 And although certain national and international laws have curbed oil spills and dumping by cruise ships, the amount of contaminants accumulating in oceans grows, even as the oceans’ ability to dilute these substances declines.3

Many substances that are carried into the world’s rivers and streams eventually find their way into coastal waterways and oceans. Around 60 percent of the wastewater discharged into the Caspian Sea is untreated, for example, while in Latin America and the Caribbean the figure is close to 80 percent and in large parts of Africa and the Indo-Pacific region the proportion is as high as 90 percent.4 In the United States alone, more than 3.2 trillion liters of sewage—including human waste, detergents, and household chemicals—gush untreated into waterways every year.5 Worldwide, an estimated $56 billion is needed annually to address this enormous wastewater problem.6 By some estimates, the fastest-growing source of ocean pollution is the chemicals, human waste, and trash that run off of coastal city streets into ocean-bound storm drains.7

More than half of the world lives in coastal areas (within 200 kilometers of shore) that cover just 10 percent of Earth’s surface.8 These coastal populations are increasing at twice the rate of inland ones.9 An estimated 70 percent of the world’s tropical coasts have been developed for housing, fish farms, or industrial ports, and the United Nations expects 90 percent will be developed by 2032.10

Nitrogen, phosphorus, and other nutrients from fertilizers, large livestock farms, and septic systems provoke explosive blooms of tiny plants known as phytoplankton, which die and sink to the bottom and then are eaten by bacteria that use up the oxygen in the water.11 This oxygen starvation creates “dead zones” that make it difficult for fish, oysters, sea grass beds, and other marine creatures to survive.12 There are now about 200 of these zones around the world, roughly one third more than just two years ago.13 The most severe cases exceed 20,000 square kilometers, as in the Gulf of Mexico, the Bay of Bengal, the Arabian Sea, the East China Sea, and the Baltic Sea.14

The U.N. Environment Programme (UNEP) estimates that 46,000 pieces of plastic litter— including bits of packaging, cigarette lighters, plastic bags, and diapers—are floating on every square mile of the oceans, a figure that has increased threefold since the 1960s.15 Marine conservation groups estimate that more than a million seabirds and 100,000 mammals and sea turtles die globally each year by getting tangled in or ingesting plastics.16

Even pollution of the atmosphere—in the form of greenhouse gases and resulting climate change—is taking a growing toll on ocean life. Climate change is altering fish migration routes, pushing up sea levels, leading to more coastal erosion, raising ocean acidity levels to a point where they threaten calcium-building species like corals and shellfish, and interfering with ocean currents that move vital nutrients upward from the deep sea.17 The latter generates chaos among plankton, the foundation of the ocean food chain, that ironically help store carbon dioxide in the ocean floor as they die and decompose; the oceans have absorbed about half of the carbon dioxide produced by humans in the last 200 years.18

Humans suffer, of course, when ocean pollution reduces fish populations or stains the pristine nature of beach recreation. Industrial pollutants, like mercury or PCBs, that end up in water bodies are absorbed by fish we eat. In the last half-century, scientists around the world have tracked a 10-fold increase in pollution-fed algae blooms, which have produced toxins that poison sea life, seafood, and even humans swimming in and living near the ocean.19

Some of the most pernicious forms of ocean pollution are generated by the very people and industries that benefit directly from the pristine nature of the seas. Lax state and federal antipollution laws allow the world’s growing fleet of more than 200 cruise ships to dump into the ocean untreated sewage from sinks and showers and inadequately treated sewage from toilets.20 Once ships are three miles from shore, they can dump all untreated sewage, including bacteria, pathogens, detergents, and heavy metals. Each day, a standard cruise ship generates some 114,000 liters of sewage from toilets; 852,000 liters of sewage from sinks, galleys, and showers; seven tons of garbage and solid waste; 57 liters of toxic chemicals; and 26,500 liters of oily bilge water.21

Oceana, an international ocean protection group, launched a campaign to introduce Clean Cruise Ship legislation in California and at the U.S. federal level to prohibit dumping of boat sewage.22 And following an aggressive 11-month grassroots campaign aimed at the world’s second largest cruise line, Royal Caribbean agreed to install advanced wastewater treatment technology on all 29 of its ships.23

Since its formation in 1995, UNEP’s Global Programme of Action for the Protection of the Marine Environment from Land-Based Sources has helped reduce oil discharges and spills into the oceans by 63 percent compared with levels in the mid-1980s.24 And tanker accidents have dropped by 75 percent, partly as a result of the shift to double-hulled tankers.25

The general public, perhaps because people care about eating seafood or because the oceans seem worth protecting, is also beginning to clean up pollution. Beginning in 1986, the Ocean Conservancy organized shoreline cleanups each fall.26 To date, 6.2 million volunteers in International Coastal Cleanups have removed 49 million kilograms of debris from nearly 288,000 kilometers of coasts in 127 nations.27 Nearly 60 percent of all debris is from recreational activities, including fishing lines and nets, beach toys, and food wrappers. An additional 29 percent is cigarette butts and filters.28