Our oceans are constantly changing, and while some of these changes are natural occurrences, human activity has led to several other changes that are detrimental to the health of these ecosystems. The White House Council on Environmental Policy identifies overfishing, pollution, climate change and coastal development as some of the most serious environmental problems affecting oceans. Oceans are a global resource, which makes setting standards for their use and care difficult; however, several organizations work to combat these environmental issues on a local scale.
Several species of whale, crab, shellfish and game fish have been threatened by overfishing; so many members of these species are caught by fishermen that the natural populations cannot sustain themselves. Some countries, like the United States, have set annual catch limits for all species that are commercially caught in an effort to end overfishing. However, overfishing of some populations is so severe that they may only rebound with intense intervention. For example, the Nature Conservancy is working to restore Half Moon Reef off the coast of Texas. Early in the 20th century, oyster shells became a popular building material and oyster beds like the one at Half Moon Reef were dredged until they disappeared. Oysters filter water and are essential to the health of the ecosystem in the Gulf of Mexico, so the restoration of these oyster beds will improve the habitat for several species.
The oceans are absorbing some of the excess heat being trapped in the atmosphere by greenhouse gases, such as carbon dioxide, according to the U.S. Environmental Protection Agency. Climate change is causing ocean surface temperatures to rise, as well as melting polar ice and increasing sea levels. The level of carbon stored in the ocean is also increasing as emissions of carbon dioxide increase. This dissolved carbon is increasing the acidity of seawater, which influences several species. For example, coral and shellfish have trouble building shells and skeletons because the carbon changes the mineral content of the water.
Human activity on land creates the majority of the pollution in the oceans, according to the National Atmospheric and Oceanic Administration. Vehicles, septic tanks and industrial and agricultural operations all deposit chemicals and toxins on the ground that are washed into the oceans during rainstorms. A large portion of shellfish habitats in U.S. waters has been negatively affected by this type of pollution. Larger pieces of garbage and debris are gathered by ocean currents into floating garbage patches that entangle large marine animals and confuse birds that often mistake bits of plastic for food.
Approximately half of the U.S. population lives in counties that are on the coasts. Residential and commercial development on ocean coasts destroys wildlife habitats and increases water pollution. Occasionally, catastrophic events damage coastal developments with disastrous consequences. When a tsunami hit Japan in 2011, the Fukushima Daiichi nuclear power plant was severely damaged and substantial amounts of radioactive material were leaked into the ocean. Radioactive particles were dispersed by the ocean, polluting the water and adversely affecting fish populations.
- The White House Council on Environmental Policy: Final Recommendations of the Interagency Ocean Policy Task Force
- Nature Conservancy: Texas: Half Moon Reef
- NOAA Fisheries: Status of Stocks 2012
- National Atmospheric and Oceanic Administration: Most Ocean Pollution Begins on Land
- Smithsonian National Museum of Natural History: Ocean Trash Plaguing Our Sea
- United States Environmental Protection Agency: Climate Change Indicators in the U.S.: Oceans
- New England Aquarium: Climate Change and the Oceans
- National Atmospheric and Oceanic Administration: Cumulative and Secondary Impacts of Development
- World Nuclear Association: Fukushima Accident
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