The Ocean

Photo: Logging tracks near New Orleans

Pollution, logging, dredging, draining of wetlands, and coastal development are all factors that lead to marine habitat destruction. The absence of cypress swamps (shown here), decimated by logging and saltwater intrusion from manmade canals, is among the factors that led to New Orleans' devastation during Hurricane Katrina.

Photograph by Tyrone Turner

Habitat destruction occurs when the conditions necessary for plants and animals to survive are significantly compromised or eliminated.

Most areas of the world's oceans are experiencing habitat loss. But coastal areas, with their closeness to human population centers, have suffered disproportionately and mainly from manmade stresses. Habitat loss here has far-reaching impacts on the entire ocean's biodiversity. These critical areas, which include estuaries, swamps, marshes, and wetlands, serve as breeding grounds or nurseries for nearly all marine species.

Causes of Ocean Habitat Loss

Humans and Mother Nature share blame in the destruction of ocean habitats, but not equally.

Hurricanes and typhoons, storm surges, tsunamis and the like can cause massive, though usually temporary, disruptions in the life cycles of ocean plants and animals. Human activities, however, are significantly more impactful and persistent.

Wetlands are dredged and filled in to accommodate urban, industrial, and agricultural development. Cities, factories, and farms create waste, pollution, and chemical effluent and runoff that can wreak havoc on reefs, sea grasses, birds, and fish.

Inland dams decrease natural nutrient-rich runoff, cut off fish migration routes, and curb freshwater flow, increasing the salinity of coastal waters. Deforestation far from shore creates erosion, sending silt into shallow waters that can block the sunlight coral reefs need to thrive.

Destructive fishing techniques like bottom trawling, dynamiting, and poisoning destroy habitats near shore as well as in the deep sea.

Tourism brings millions of boaters, snorkelers, and scuba divers into direct contact with fragile wetland and reef ecosystems. Container ships and tankers can damage habitat with their hulls and anchors. Spills of crude oil and other substances kill thousands of birds and fish and leave a toxic environment that can persist for years.

Climate Change

Perhaps the most devastating of all habitat-altering agents, however, is climate change. Scientists are still coming to grips with the consequences that excessive atmospheric carbon dioxide and Earth's rapid warming are having on ecosystems. But there is ample evidence indicating that the oceans are bearing the brunt of these changes.

As Earth's temperature rises, it is primarily the oceans that absorb the extra heat. Even small temperature changes can have far-reaching effects on the life cycles of marine animals from corals to whales.

In addition, warmer temperatures cause excess melting of ice caps and glaciers, raising sea levels and flooding estuaries.

High levels of atmospheric carbon dioxide, caused mainly by the burning of fossil fuels, are absorbed by the oceans, where the gas dissolves into carbonic acid. This elevated acidity inhibits the ability of marine animals, including many plankton organisms, to create shells, disrupting life within the very foundation of the ocean's food web.

Sea Changes

Ongoing efforts to safeguard ocean habitats include the creation of gigantic marine sanctuaries where development is curtailed and fishing is prohibited. Laws banning the dumping of sewage and chemicals into the ocean and policies that foster better stewardship of wetlands are having positive effects. But scientists agree that drastic measures will be needed to avert the ocean crises being created by climate change.

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Did You Know?

Bottom trawling, in which a giant net is dragged along the ocean floor, is widely considered to be the most destructive form of commercial fishing.

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