Brian Barton
Marine pollution is a pressing environmental issue that poses a threat to the health of our planet. Oceans cover over 70% of the Earth's surface and are among the world's most valuable natural resources, playing a crucial role in governing the weather, cleaning the air, providing food, and supporting a diverse range of marine life. Unfortunately, human activities have led to the degradation of ocean health through various forms of pollution, including toxic chemicals, sewage, fertilisers, plastics, oil spills, and noise from shipping and drilling. The majority of marine pollution, approximately 80%, originates from land-based sources, whether through runoff, littering, poor waste management, or extreme natural events such as tsunamis and hurricanes. As a result, marine ecosystems and wildlife are suffering, and the economic structures that depend on them are also impacted.
| Characteristics | Values |
|---|---|
| Percentage of marine pollution that comes from land | 80% |
| Main types | Chemicals and trash |
| Examples of chemical pollutants | Nitrogen, phosphorus, crude oil, antifoulants, pesticides, pharmaceuticals, personal care products |
| Examples of trash pollutants | Plastic, sewage, fertilisers, discarded fishing nets, noise from shipping and drilling |
| Causes of trash pollution | Littering, illegal dumping, poor waste disposal practices, stormwater discharge, extreme natural events like tsunamis, accidental spills, deliberate dumping, untreated effluent, atmospheric fall-out, run-off from drains and rivers |
| Causes of chemical pollution | Use of fertilizer on farms, nonpoint source pollution, point source pollution |
| Examples of nonpoint source pollution | Septic tanks, cars, trucks, boats, farms, ranches, forest areas |
| Examples of point source pollution | Oil spills, chemical spills, discharge from faulty or damaged factories or water treatment systems |
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What You'll Learn
Land-based sources
Eighty percent of marine pollution comes from land-based sources. This includes pollution from far inland, which gradually makes its way to the ocean via storm drains, sewers, and other routes.
One of the biggest sources of marine pollution is nonpoint source pollution, which occurs as a result of runoff. Nonpoint source pollution includes many small sources, such as individual cars, trucks, boats, and septic tanks, as well as larger sources, such as farms, ranches, construction sites, and forest areas. For example, millions of motor vehicle engines drop small amounts of oil onto roads each day, which is then washed into the sea. Similarly, dirt, topsoil, or silt from fields or construction sites can run off into waterways, harming fish and wildlife habitats. Nonpoint source pollution can also come from manufacturing plants that release toxic waste, including mercury, into the ocean.
Another significant contributor to marine pollution is plastic waste, which accounts for an estimated 171 trillion plastic particles in the world's oceans. Plastic pollution comes from single-use plastic items such as water bottles, drinking straws, and plastic bags, which are often littered or improperly disposed of. These plastics can persist in the environment for hundreds of years, polluting beaches, entangling marine life, and being ingested by animals. Plastic debris has even been found at the bottom of the deepest ocean trenches.
In addition to nonpoint source pollution and plastic waste, land-based sources of marine pollution include atmospheric pollution, such as carbon emissions from burning fossil fuels, and accidental spills or deliberate dumping of toxic chemicals. These toxic chemicals, including crude oil and other petroleum products, pesticides, and pharmaceuticals, can have harmful effects on marine ecosystems and human health.
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Nonpoint source pollution
One of the main issues with nonpoint source pollution is that it can be challenging to identify the exact causes and implement effective solutions. The pollutants in this type of pollution can be harmful to both ecosystems and the economy. For example, pollution can lead to mass die-offs of fish and dirty-looking water, which can result in financial losses for industries that depend on marine resources, such as fishing and tourism.
Another significant contributor to nonpoint source pollution is atmospheric deposition, where pollutants are deposited from the atmosphere into water bodies. This can include carbon emissions from burning fossil fuels, which can lead to ocean acidification and have detrimental effects on marine ecosystems. Additionally, dirt, silt, and topsoil from construction sites and crop fields can run off into waterways, harming fish and wildlife habitats.
Efforts are being made to address nonpoint source pollution, such as the Coastal Zone Management Program by NOAA, which aims to create control plans for coastal states. The EPA has also developed fact sheets and programs to help control and reduce nonpoint source pollution, particularly in agriculture.
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Oil spills
To address the issue of oil spills, measures have been implemented to reduce their occurrence and enforce accountability. For instance, the Oil Pollution Act of 1990 established that those responsible for oil spills are liable for the cleanup and restoration costs. Additionally, amendments to MARPOL in 1992 made it mandatory for large tankers to have double hulls, significantly reducing the number and severity of oil tanker spills.
While progress has been made in mitigating the impact of oil spills, they continue to pose a significant threat to marine environments and the industries that depend on them. The ongoing challenge is to minimize the occurrence of oil spills, improve cleanup techniques, and enhance the rehabilitation of affected ecosystems and communities.
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Plastic pollution
A large portion of marine plastic pollution originates from land-based sources. Rivers play a crucial role in transporting plastic from land to the sea, with 70% to 80% of ocean plastics entering through this pathway. The top contributing rivers are found in Asia, with the Philippines accounting for more than one-third of plastic inputs. Factors such as population density, GDP per capita, terrain, and proximity to coastlines influence the amount of plastic that ends up in the oceans.
Urban runoff, littering, industrial activities, tyre abrasion, construction, and agriculture are significant sources of land-based plastic pollution. Single-use products, such as bottles, caps, cigarettes, shopping bags, cups, and straws, contribute significantly to the problem. Improper waste management, including the lack of recycling, incineration, or proper landfill disposal, exacerbates the issue.
Ocean-based sources also contribute to marine plastic pollution, accounting for about 20% to 30% of the total. Discarded fishing gear, ropes, lines, and abandoned vessels are among the key ocean-based sources. Additionally, paint shed from shipping and discharges from ships add to the pollution.
The impact of marine plastic pollution on wildlife is devastating. It affects a wide range of marine animals, including fish, turtles, seals, crustaceans, seabirds, and marine mammals. Ingestion of plastic waste, entanglement, starvation, suffocation, and internal injuries are common consequences, leading to reduced ability to swim and fly, and even death. The durability of plastic means that once it enters the ocean, it persists for long periods, continuously harming marine life.
Addressing marine plastic pollution requires a global approach. While some countries have taken positive steps, such as banning certain single-use plastics, a comprehensive international treaty is necessary to significantly reduce plastic production, phase out harmful practices, and improve waste management practices. Education and public awareness are also crucial in preventing littering and promoting sustainable alternatives.
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Carbon emissions
Marine pollution is a pressing issue, with the ocean absorbing about a quarter of all man-made carbon emissions. This is causing ocean acidification, which has severe ecological, economic, and health consequences.
Ocean acidification poses a severe threat to marine life. It destroys coral reefs, impairs the development of shellfish, dissolves calcium-containing microorganisms at the base of the food web, and increases the toxicity of some pollutants. The increased acidity of the ocean water can have far-reaching consequences for the entire marine ecosystem and the coastal economies that depend on it.
Human activities, such as industrial processes and the use of fossil fuels, are the primary sources of carbon emissions that contribute to marine pollution. These activities release excessive amounts of CO2 into the atmosphere, which is then absorbed by the oceans. Additionally, vessels and ships contribute to carbon emissions through their exhaust gases. Measures like the London Convention/London Protocol and the regional OSPAR Convention have been enacted to regulate the injection of carbon dioxide into sub-seabed geological formations to mitigate climate change.
To address the issue of carbon emissions and marine pollution, strategies such as Carbon Capture and Storage (CCS) have been proposed. CCS involves capturing CO2 directly at industrial or power plant sources and storing it in secure subsurface reservoirs. While this technology shows promise, it is important to recognize that reducing carbon emissions at their source is crucial to mitigating their impact on marine environments.
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Frequently asked questions
Marine pollution comes from a variety of sources, most of which are land-based human activities. These include nonpoint source pollution, which is the accumulation of pollution from small sources like vehicles, farms, and septic tanks, as well as point source pollution, which comes from a single source like an oil spill or chemical discharge.
Land-based pollution can reach the oceans through various pathways. One common way is through runoff, where rain or snow moves pollutants from the ground into rivers and oceans. Pollution can also be blown into the ocean by wind or enter through storm drains, sewers, and rivers.
Marine pollution has severe impacts on the environment and wildlife. Chemical pollution, such as nitrogen and phosphorus, can cause harmful algal blooms, which deplete oxygen levels in the water and create "dead zones" where marine life cannot survive. Oil spills coat marine animals, suffocating them or impairing their ability to move and reproduce. Plastic pollution entangles marine animals and is often ingested, leading to health issues and death. Marine pollution also disrupts the food chain, with toxic chemicals accumulating in marine organisms and impacting human health.
