Habitat destruction is one of five global ecological pressures affecting the ocean, along with fishing pressure, climate change (including ocean acidification, water pollution and the introduction of alien species or genotypes.    

Damage or destruction of habitats kills the plants and animals responsible for the habitat's ecological functions and, in some cases, its survival  and regeneration.  This pressure focuses on destruction of intertidal habitats and two types of subtidal habitats, soft bottom and hard bottom.  These habitats include coral reefs, sea grasses and mangrove forests, but do not include sea ice, which is accounted for elsewhere. 

The background photo for this page shows a coral reef at Raja Ampat, Indonesia, that was destroyed by use of dynamite for blast fishing.

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. Seagrass meadows are included in this category.

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” includes tropical coral reefs, but can also be used in reference to human-made structures such as jetties and fabricated reefs. The Ocean Health Index does not assess human-made structures.   

Intertidal Habitats

Intertidal habitats are located between low and high tide lines and can be either soft or hard bottom. The intertidal zone's area varies geographically depending on tidal range as well as coastal and submarine topography. Plants and animals of the intertidal zone are exposed to air at low tide but immersed in seawater at high tide, so must withstand cyclic fluctuations of temperature, desiccation, strong light (including UV), wave action, and predation by terrestrial and marine species. Mangrove forests and salt marshes are among the habitats included in this category.