Coast

In wave-protected areas, they harbor salt marshes, mangroves or seagrasses, all of which can provide nursery habitat for finfish, shellfish, and other aquatic animals.

[3][4] Rocky shores are usually found along exposed coasts and provide habitat for a wide range of sessile animals (e.g. mussels, starfish, barnacles) and various kinds of seaweeds.

According to an atlas prepared by the United Nations, about 44% of the human population lives within 150 km (93 mi) of the sea as of 2013[update].

[7] The interactive effects of climate change, habitat destruction, overfishing, and water pollution (especially eutrophication) have led to the demise of coastal ecosystem around the globe.

Marine scientists think of the "wet" (aquatic or intertidal) vegetated habitats as being coastal ecosystems (including seagrass, salt marsh etc.)

[citation needed][15] Government authorities in various countries may define coast differently for economic and social policy reasons.

Although the "paradox of length" was previously noted by Hugo Steinhaus,[16] the first systematic study of this phenomenon was by Lewis Fry Richardson,[17][18] and it was expanded upon by Benoit Mandelbrot.

Tides do not typically cause erosion by themselves; however, tidal bores can erode as the waves surge up the river estuaries from the ocean.

Macrotidal coasts lack barrier islands and lagoons, and are characterized by funnel-shaped estuaries containing sand ridges aligned with tidal currents.

The Earth's natural processes, particularly sea level rises, waves and various weather phenomena, have resulted in the erosion, accretion and reshaping of coasts as well as flooding and creation of continental shelves and drowned river valleys (rias).

Supporting services of coastal ecosystems include nutrient cycling, biologically mediated habitats and primary production.

In contrast, a submergent coastline is one where the sea level has risen, due to a global sea-level change, local subsidence, or isostatic rebound.

[31] High energy coasts are exposed to the direct impact of waves and storms, and are generally erosional environments.

Steep waves that are close together and break with the surf plunging down onto the shore slope expend much of their energy lifting the sediment.

Historically, the Ligurian Riviera extended from Capo Corvo (Punta Bianca) south of Genoa, north and west into what is now French territory past Monaco and sometimes as far as Marseille.

[36] As a result of the fame of the Ligurian rivieras, the term came into English to refer to any shoreline, especially one that is sunny, topographically diverse and popular with tourists.

[47] In coastal environments, the littoral zone extends from the high water mark, which is rarely inundated, to shoreline areas that are permanently submerged.

The locations of these beds show the extent of ancient seas at particular points in geological time, and provide clues to the magnitudes of tides in the distant past.

Some coastal animals are used to humans in developed areas, such as dolphins and seagulls who eat food thrown for them by tourists.

Since the coastal areas are all part of the littoral zone, there is a profusion of marine life found just off-coast, including sessile animals such as corals, sponges, starfish, mussels, seaweeds, fishes, and sea anemones.

Mangroves, seagrasses, macroalgal beds, and salt marsh are important coastal vegetation types in tropical and temperate environments respectively.

The most important ones are: The pollution of coastlines is connected to marine pollution which can occur from a number of sources: Marine debris (garbage and industrial debris); the transportation of petroleum in tankers, increasing the probability of large oil spills; small oil spills created by large and small vessels, which flush bilge water into the ocean.

Marine pollution occurs when substances used or spread by humans, such as industrial, agricultural and residential waste, particles, noise, excess carbon dioxide or invasive organisms enter the ocean and cause harmful effects there.

Air pollution is also a contributing factor by carrying off iron, carbonic acid, nitrogen, silicon, sulfur, pesticides or dust particles into the ocean.

Floating oceanic debris tends to accumulate at the center of gyres and on coastlines, frequently washing aground, when it is known as beach litter or tidewrack.

Microplastics are beads of plastic less than 5 millimeters wide,[62] and they are commonly found in hand soaps, face cleansers, and other exfoliators.

When these products are used, the microplastics go through the water filtration system and into the ocean, but because of their small size they are likely to escape capture by the preliminary treatment screens on wastewater plants.

The microplastics are such a concern because it is difficult to clean them up due to their size, so humans can try to avoid using these harmful plastics by purchasing products that use environmentally safe exfoliates.

[68]: 5, 8  Between 1993 and 2018, melting ice sheets and glaciers accounted for 44% of sea level rise, with another 42% resulting from thermal expansion of water.

[69]: 1576 International attention to address the threats of coasts has been captured in Sustainable Development Goal 14 "Life Below Water" which sets goals for international policy focused on preserving marine coastal ecosystems and supporting more sustainable economic practices for coastal communities.