Habitat Destruction

Habitat damage, destruction or loss occurs when natural events or human actions harm or kill plants and animals that are essential to the habitat’s survival and regeneration. Habitat destruction can take place in any area of the ocean and may have long-lasting or permanent effects if habitat conditions physically or biologically prevent regeneration.

Soft Bottom [Subtidal] Habitats

Soft bottom environments include habitats where the seabed consists of fine grain sediments, mud and sand. Soft bottom habitats vary in terms of biodiversity and productivity, depending upon depth, light exposure, temperature, sediment grain size and abundance of microalgae and bacteria.

Soft bottom is the ocean’s largest habitat, forming the bottom of most of the continental shelves as well as vast expanses at depths of 3,000 to 6,000 m, which cover more than 60 percent of Earth’s surface (Snelgrove 2010; Ausubel et al. 2010)

Hard Bottom [Subtidal] Habitats

Hard bottom habitats underlie all soft bottoms and include all types of exposed rock or coral and associated flora and fauna. Hard bottom areas are located throughout the ocean, and include the mid-ocean ridge and seamounts, but are more frequently found near the coast. The term “hard bottom” also refers to man-made structures, including jetties and fabricated reefs.

Intertidal Habitats

Intertidal habitats are located between low and high tide lines and can be either soft or hard bottom. The area of an intertidal zone depends upon a given area’s tidal ranges and submarine topography. Exposure in low tide conditions and immersion in high means organisms in these habitats are affected by wave action, cyclic fluctuations of temperature, exposure to air, ambient light, and predation by terrestrial and marine species.

Causes & Impacts Of Habitat Destruction
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Which Goals Does This Affect?


How Was It Measured?

The subtidal soft bottom destruction proxy utilized global commercial catch data developed by the Sea Around Us project, based upon FAO and other source data, in order to determine catch (tonnes per year) from trawling for each year from 1950-2006. ‘Trawlable habitat’ within an EEZ was defined as shallow subtidal (0-60m) and outer shelf (60-200m) soft bottom habitat from Halpern et al (2008). Total trawled catch was divided by the total area of soft-bottom habitat to produce a measure of trawl intensity per unit area.

The subtidal hard bottom destruction proxy scored regions based upon data from Reefs at Risks Revisited, which recorded the presence of destructive artisanal blast and poison (cyanide) fishing on a country-level basis.  Destructive artisanal fishing practices were given a maximum value of “1” and those areas under low threat were categorized as “0”. These data were not a perfect proxy, as they only cover coral reef habitats, however, suitable global data for additional hard bottom habitats were not available.

The intertidal habitat destruction proxy measured the coastal population density within 10 km of the coast based upon the assumption that the potential for intertidal habitat destruction was proportional to the density of human population living along the coast.  Population density was extracted from the gridded population of the world dataset (CIESIN 2005), using only the UN-adjusted population counts and density for the most recent year, 2000.

What Are The Impacts?


ECOLOGICAL IMPACT
Habitat destruction can have a significant impact on marine biodiversity as species’ richness, abundance, distribution, genetic variation and inter-population dynamics are affected and entire ecosystems are altered by the loss of habitat.

Destructive fishing practices (e.g. dredging, bottom trawling, shrimp farming, dynamiting, and poisoning) can displace or destroy habitats, eliminating food, shelter and breeding grounds for numerous species and decreasing primary production due to increased sedimentation.

When seagrass, mangrove and salt marsh habitats are destroyed, they are no longer able to sequester carbon dioxide (CO2) from the atmosphere and significant amounts of CO2, released from stored carbon, are emitted back into the atmosphere.

Ships can damage habitats with their hulls, propellers and anchors.

Divers and snorkelers can damage habitats such as coral reefs and seagrasses when in direct contact (i.e. breaking and trampling).

The installation and maintenance of pipelines and fiber optic cables on the seafloor can damage marine ecosystems and result in sedimentation and pollution.
HUMAN HEALTH IMPACT
Marine plants and animals are an important biological source of unique chemicals with potential for medical use.

More than half of all new cancer drug research is focused on marine organisms (Cesar et al. 2003).

Habitat destruction can result in a loss in commercially or recreationally important marine species, potentially impacting opportunities for exercise, relaxation or outdoor learning.

The destruction and loss of coastal habitats decreases shoreline protection, which can negatively impact human lives and property.

Habitat destruction can eliminate organisms that filter sediments and pollutants, reducing water quality and impacting human health.
ECONOMIC IMPACT
Loss and destruction of habitat for commercially harvested species (food and natural products) can reduce food and livelihood security.

Decreased shoreline protection due to habitat loss can affect coastal communities and industries that are exposed to climactic events (e.g. storms, floods).

Currently, half of the world population lives within 60 km of the ocean and three-quarters of the large cities are located by the coast. By 2020, it is projected that some 60 per cent of the world population (~ 6 billion) will live in coastal areas (Kennish 2002, in UNEP 2007).


What Has Been Done?


Get More Information

The United Nations Environment Programme (UNEP) GRID-Arendal 
The UNEP supports informed decision-making and promotes awareness regarding habitat destruction.    

Oceana    
Oceana works internationally to alleviate problems including overfishing, acidification and habitat destruction through policy-oriented campaigns.    

Save our Seas Foundation 
This foundation raises awareness regarding the degradation of coastal ecosystems and supports marine research worldwide.  

U.S. Office of Naval Research (ONR)    
ONR provides a guide to several marine habitats and addresses the impacts humans can have upon these environments.

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References




PHOTO(S): © Keith A. Ellenbogen
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