Coastal Zone Pressure: Habitat Loss, Economic Development, and Future Threats

Regardless of how the coastal zone is defined, approximately 40 percent of the world’s population and 60 percent of the world’s economic production are concentrated in a 100-kilometer swath along the world’s coasts. The confluence of such a significant proportion of the world’s population on the narrow fringe separating the marine and terrestrial realms has significant ecological and socioeconomic implications.

Habitat loss due to the destruction of larger vascular vegetation, upon which many species depend for food and shelter, is probably the most serious threat to biodiversity in terrestrial environments. Loss of marine habitat is primarily a concern in coastal, near-shore, and intertidal marine environments. Increasing pressure on coastal systems has come from a combination of shipping and its attendant infrastructure, modification of natural coastlines, bottom-contact fishing (e.g., trawling), recreational activities, and increased land runoff—including nutrients and suspended solids. The types of habitats in these areas that can be “lost” include marine macrophytes (kelp), mangroves, seagrasses, corals, and other biotic communities (e.g., sponges, sea pens, sea fans, aphotic corals).

Abiotic habitats can be affected as well, such as intertidal and estuarine mudflats and other areas that are dredged or subject to dumping. Habitat loss in deeper marine environments and the pelagic ocean is more difficult to determine, as these habitats are primarily composed of either oceanographic (e.g., currents, gyres, fronts) or physiographic (e.g., seabed composition) structures and processes that are either not immediately affected or are more resilient to human activities. Loss of marine habitat is significant not only from an ecological perspective but increasingly from a socioeconomic perspective as well. The interaction of human effects and natural marine processes is most evident in coastal waters where strategies to prevent habitat loss or restore habitats are integrated within coastal zone management initiatives.

Habitat loss can be rapid and its consequences significant. An estimated kilometer of Europe’s coastline was developed each day between 1960 and 1995, resulting in a 50 percent loss of coastal wetlands and seagrasses. Much of the world’s continental shelves have experienced habitat degradation due to bottom-contact fishing (bottom trawling), where nets are dragged over the ocean floor causing damage to corals and seagrasses and changes to the benthic (bottom) fauna living on or near the seabed. Furthermore, bottom- contact fishing can result in fine sand, silts, and clays being resuspended in the water column for extended periods.

In addition, as natural resources become depleted or more difficult to access on land, the pressure to extract material from the oceans increases. The near-shore marine environment has long been utilized as a source for materials. For centuries, beaches and near-shore areas have been mined for gold (Au), tin (Sn), diamonds, sand, and gravel. As mining and shipping technologies improve, exploration and development have radiated seaward onto the continental shelves. Offshore oil drilling was pioneered in the 1930s in the Gulf of Mexico, and the first offshore wind farm was established in Denmark in the 1990s. Currently, one-third of the world’s petroleum is produced from continental shelves. This output is likely to continue to increase as sea ice retreats in the polar regions, opening up new areas for exploration and development.

It is estimated that deep-sea areas (outside of continental shelves) contain two-thirds of the world’s mineral wealth. For the past sixty years, anticipated global mineral shortages have created periods of interest in mining the mineral-rich deep sea. However, these prognosticated shortages have failed to transpire due to a combination of increased metal recycling, refinements in industrial processes, and new terrestrial discoveries. This has made it cost-prohibitive for deep-sea mining to become economically attractive. The rapid industrialization of China and India may recently alter this dynamic as mineral prices are currently being driven to a point where commercial deep-sea mineral production may soon be profitable. Long-term demand—based on the forecasted development of land- based deposits—suggests that marine deposits high in zinc (Zn) and enriched in silver (Ag) are expected to become commercially viable at some point in the future.

A final potential future impact on continental shelf environments is methane hydrates. Produced by the decomposition of organic materials, methane hydrates consist of molecules of natural gas (predominantly methane) trapped in ocean sediments by a combination of low temperature and high pressure. They are generally found in water depths greater than 400 to 500 metres and up to 1,100 metres below the sea floor. One cubic meter of hydrate is equivalent to 164 m³ of methane at atmospheric pressure and temperature, and the energy potential of the world’s reserves is estimated between 10⁵ and 10⁸ trillion standard ft³ (TCF). These astounding numbers make the energy potential of methane hydrates greater than all the world’s known coal, oil, and natural gas reserves.