Difference between revisions of "Threats to the coastal zone"

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This article provides a review of human activities which put pressure on coastal ecosystems and habitats. It discusses generic modifications to coastal ecosystems in relation to specific human activities and introduces the various threats resulting from poorly managed activities.
 
  
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==Living resources==
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In this section on [[Living resources]] we will look at how and why ecosystems are at risk, despite the fact that humans are increasingly dependant on resources from the sea, particularly coastal areas.
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This article presents an introduction to '''threats to the coastal zone''' that result from human activities and pressures. It discusses generic modifications to coastal [[ecosystem]]s in relation to specific human activities and introduces the various threats resulting from poorly managed activities.
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==Climate change==
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A study by Halpern et al. (2019<ref>Halpern, B.S., Frazier, M., Afflerbach, J., Lowndes, J.S., Micheli, F., O’Hara, C., Scarborough, C. and Selkoe, K.A. 2019. Recent pace of change in human impact on the world’s ocean. Scientific Reports 9: 11609</ref>) suggests that climate change is currently by far the most important stressor for ocean and coastal ecosystems. In this study the cumulative impact of 14 stressors related to human activities (including climate change, fishing, land-based pressures, and other commercial activities) on 21 different marine ecosystems globally was estimated for each of eleven years spanning 2003–2013. The increase of the estimated cumulative impact for the global ocean was estimated to be due for more than 90% to increasing sea surface temperature and acidity and the increase of the estimated cumulative impact for the coastal zones was estimated to be due for more than 80% to increasing sea surface temperature and sea level.
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Other results regarding threats resulting from climate change are dealt with elsewhere in the Coastal Wiki, see the page [[Climate change]] and the links and references therein.
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==Fisheries==
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The reader is referred to the separate pages [[Effects of fisheries on marine biodiversity]] and [[Mariculture]]. These articles discuss how and why ecosystems are at risk, while the human demand of resources from the sea is increasing, particularly in coastal areas.
  
 
==Water quality/pollution==
 
==Water quality/pollution==
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Coastal and estuarine ecosystems have been, and still are, heavily influenced by the human species through pollution and habitat loss throughout the world. Examples of environmental issues include the enrichment of enclosed waters with organic matter leading to eutrophication, pollution by chemicals such as oil, and sedimentation due to land-based activities or sea-level rise due to the global change. Over 80% of all marine pollution originates from land-based sources which are primarily industrial, agricultural and urban. Pollution accompanies most kinds of human activities, including offshore oil and gas production and marine oil transportation. The relative contribution of each of these channels into the combined pollution input into the sea will be different for different substances and in different situations. Quantitative estimates of these processes are difficult because of the lack of reliable data and the extreme complexity of biogeochemical cycles, especially at the sea-land and sea-atmosphere interfaces.
 
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Point and non-point source pollutions continue globally, resulting in the steady degradation of coastal and marine ecosystems. Indirect (or diffuse) inputs are usually widespread, low-level discharge often likely to result in chronic pollution. In this section, generic sources of pollution and effects (eutrophication, contamination and pollution from industry and agriculture, etc.) are considered. The sensitivity of the coastal zone to watershed impacts is examined in relation to land-derived pollution and water quality.
 
  
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GESAMP (the United Nations Group of Experts on the Scientific Aspects of Marine Pollution) has given a useful definition of pollution:
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[[image:Grebe-with-oil.jpg|thumb|right|150px|Oil pollution victim.]]
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{{Definition|title=Pollution
 
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|definition=The introduction, directly or indirectly, of substances or energy into the marine environment resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to marine activities, including fishing, impairment of quality of use of sea-water and reduction of amenities<ref> GESAMP (the United Nations Group of Experts on the Scientific Aspects of Marine Pollution)</ref>.
 
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}}
 
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Contamination is usually considered to occur when an input of waste from human activities increases the concentration of a substance in seawater, sediments or an animal above the background level for that area or animal, but without any obvious effect.
 
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===Agriculture===
 
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Emissions and inputs from agriculture are a significant source of pollution to the coastal zone and to the atmosphere throughout the world. The contribution of agriculture to the pollution of coastal ecosystems affects biogeochemical cycles, notably in terms of:
 
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*Discharge of methane and ammonia contributing to the greenhouse effect
 
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*Use of insecticides and other pesticides affecting species, cultivated or not
 
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*Pollution, from use of oil for instance
 
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*Nutrients run-off from silage and slurry-manure, use of fertilizers leading to eutrophication
 
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====Eutrophication====
 
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((Eutrophication)) results from the increase of nutritional resources to a particular water body and includes the supply of mineral nutrients (nitrogen, phosphorus, silicon, trace elements) as well as organic carbon<ref>Richardson & Jørgensen, 1996</ref>. Discharges and emissions from land-based sources (industry, households, traffic, agriculture) provide large inputs of nutrients to coastal waters via rivers, direct discharges, diffuse sources and deposition from the atmosphere. However, eutrophication cannot be defined just in terms of an increase in nutrients concentration, as its manifestations (very often harmful to ecosystems) occur due to the existence of natural conditions, such as high temperatures and calm coastal waters.
 
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In the recent past eutrophication has been most pronounced in the developed world, but it has to be expected that it will become more and more important in the developing countries of Asia, Africa and Latin America in the near future (Nixon, 1995).  
 
  
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Additional atmospheric input of inorganic nitrogen has increased significantly to a level where it is already higher than the natural nitrogen supply in the North Atlantic Ocean basin. It is expected that the worldwide production of nitrogen (mainly from fertilizer industry and the burning of fossil fuel) will affect the biogeochemical cycles on a global scale. Unfortunately, the interactive effects of the altering N-cycle on the carbon cycle (including the dynamics of greenhouse gases within both cycles) are poorly understood.
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The separate pages [[Coastal pollution and impacts]] and [[Possible consequences of eutrophication]] discuss the way in which coastal and estuarine ecosystems have been, and still are, heavily influenced by anthropogenic pollution throughout the world. Examples of environmental issues include the enrichment of enclosed waters with organic matter leading to [[eutrophication]] and pollution by industrial chemicals and oil.  
  
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The effects of eutrophication vary from increased growth of phytoplankton, benthos and fish to changed species composition at moderate eutrophication, from blooms of nuisance causing or toxic algae to mass growth of certain species and mortality of others at severe eutrophication, and ultimately to anoxic conditions and mass mortality (fishkills). An algal biomass related phenomenon such as oxygen depletion of the water column and consequent mortality of animals can be prevented by a general reduction of nutrient discharges. At present, mathematical models on ecosystem dynamics are reliable enough to estimate dose-effect relationships. Algal species related harmful effects are less predictable. There is a general consensus that there is a global increase in harmful algal blooms. Also, there are reports which suggest a link between blooms of toxic algae and human activities such as salmon (or fish) farming. Changes in N:P:Si ratios may also cause a shift in species composition. Consequently, alterations in pelagic and benthic communities are to be expected. Which species is stimulated by eutrophication is highly dependent on the local environmental conditions.
 
  
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==Land use and coastal defences==
  
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===Industry===
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===Land use and human populations===
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Since most contaminants enter the sea by flows from the surrounding land, in particular via rivers, the highest concentrations are often found in estuaries and coastal areas and thus maximal effects of contaminants on the ecosystem could be expected to occur here. This general picture can be influenced by additional inputs from sources at sea - ships, off-shore platforms - and by inputs via the atmosphere. After entering the sea, contaminants are usually diluted and widely dispersed. However, the adsorption of contaminants to suspended solid material in the sea leads to the occurrence of elevated concentrations in the seabed in areas where this material settles. Areas, which are also close to direct sources of input, are doubly at risk as for estuaries and lagoons.
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Some 40% of the world’s human population live not far from the coast, within about 100 kilometers of the shore <ref name=A>Agardy, T. and Alder, J. (coordinating authors) 2005. Millennium Ecosystem Assessment Chapter 19 Coastal Systems. [https://www.millenniumassessment.org/documents/document.288.aspx.pdf]</ref>. This means that about 3 billion people rely to some extent on coastal and marine ecosystems, habitats and resources for food, building materials, building sites, and agricultural and recreational areas, while utilising coastal areas as a dumping ground for sewage, garbage, and toxic wastes. The pressure on the living and non-living resources of the coastal zone is expected to further increase, due to growing [[urbanization]], industrialization, and transportation. This section considers physical structures and land use modification in the [[coastal zone]], and anticipated future developments (e.g. off-shore airports, wind-energy parks, land reclamation, etc.), due to an increase in human demography and increased use of [[coastal area]]s.
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Water quality is affected by toxic substances, which are persistent in the marine environment. These substances are of varying origin and composition, but they are together classed as stable or persistent, and have decisive properties in common. They are not readily degradable, or not at all degradable, toxic to living organisms, and bio-available (living organisms can take them up and accumulate them). The persistence of certain groups of contaminants, recognised as “toxic” in the marine environment, varies. Some of the factors which have an influence include their chemical reactivity, which describes the probability for reactions with other substances, e.g. photochemical reactivity which deals with the probability of reactions initiated by light. Their biological reactivity is dependant upon the probability for different biological systems to modify or metabolise a chemical compound. In turn, the distribution and availability of chemicals in the environment depend on a number of parameters, such as:
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The tremendous population increase puts a heavy burden on the coastal zone requiring careful management. The obvious global demand for proper guidelines to cope with these increasing pressures presents the science community with a major challenge, namely to supply scientific information on possible solutions, and on the predicted effects of the different measures. There is a need for systemic studies of the ecosystems associated with large coastal urban agglomerations. Growth in the so-called mega-cities adds to a tendency of people to concentrate in the coastal zone, see the article [[Coastal cities and sea level rise]]. Clearly, this extends the range of impacts on the marine environment beyond traditional sewage and waste, adding things like increased risk of disasters, excessive noise levels and thermal.  
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*the emission, whether the contaminant is emitted as a gas, a solution, adsorbed on particles or included in a solid matrix, and
 
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*the volatility, influence the distribution of the chemical;
 
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*the lipophilicity depends on the solubility of the chemical in lipids and is one of the factors affecting accumulation in organisms;
 
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*the structure of the molecule influences the stability and the biological availability of the chemical.
 
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*The geographical distribution of pollutants is dependant on partition between different compartments. The following factors can have a significant influence:
 
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*the source pattern, whether it is a point or a diffuse source,
 
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*the wind is essential for a long range transport,
 
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*the precipitations are an important mode of transport from the air to seawater and to sediments,
 
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*the contribution from the watershed and riverine inputs are dependant upon factors such as the geology, the geomorphology, the relief…
 
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*the currents in the sea are dependant on tides, location, exposure…
 
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*the movements of organisms are another transport mode of contaminants.
 
  
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The bio-concentration or bio-accumulation of contaminants in the tissues of organisms is essential to understand. Bio-accumulation describes the ratio of a compound in the organism and the concentration in the surrounding medium. This factor is a function of the stability of the chemical but also how it will accumulate in the fat of the body, i.e. its lipophilicity. Accumulation presents a risk to consumer organisms, including the human species.
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Some of the increases in human population numbers are temporary and are due to seasonal migration. Some can be significant as for example in the Mediterranean coastal zone, which has a population of about 130 million swelling to 230 million for most of the summer, increasing transportation and pollution problems<ref>Cook, P.J. 1996. Social trends and their impacts on the coastal zone and adjacent seas. Rep. 3, British Geological Survey.</ref>. See also the articles [[Impacts originating from the tourism sector]] and [[Impact of tourism in coastal areas: Need of sustainable tourism strategy]].
  
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Bio-magnification describes a higher concentration in an organism than in its diet. It is related to the biological availability of contaminants to organisms and to their metabolism and excretion rate. Therefore, identical levels of specific contaminant can have different effects due to the fact that they can be present in different forms with different availability for uptake.
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===Coastal industries and constructions===
  
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====Organic synthetic substances====
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[[Image:LeHavrePort2000.jpg |left|400px|thumb|The port of Le Havre at the mouth of the Seine River is surrounded by a nature reserve. Photo credit Port of Le Havre.]]
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More than 7,000,000 compounds are known as Persistent Organic Compounds (POCs) and there are almost infinite possibilities to combine new substances. Serious environmental damage is caused by some of these POCs in the sea. Effects take place at metabolic and physiological levels, both in marine vertebrates and invertebrates. The great number of organic substances are due to the numerous possible substituents and substitution patterns. In fact, there are only few dangerous chemicals, and in the marine environment, the acute toxicity of compounds is only relevant after accidental spills. The only important exception to this rule is the bird casualties due to operational spills from ships of lipophilic floating substances and surfactants. The more important effects to focus on from a scientific point of view are caused by chronic exposure to relatively low concentrations and affect reproduction, immunology and carcinogenicity.
 
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In common, POCs all have the following characteristics: they are stable and toxic, and share a similar structure. It has emerged that some highly stable organic compounds - chiefly halogenated hydrocarbons - can have serious environmental effects in the sea. Such substances have in common the presence of a halogen in their molecule (chlorine, iodine, fluorine, astatine), have a low polarity ad low water solubility. Aromatic compounds are more reactive and susceptible to chemical and biochemical transformation and include pesticides (chlorinated such as DDT – DDE, Polycyclic Aromatic Hydrocarbons, Hexa Cyclo Hexan, and organometallics such as tributyltin). There are 209 congeners of Poly Chloro Biphenyls, all with different properties. This variety makes both analysis and effect studies complicated. The metabolic pathways of PCB congeners are complex. Though the use of PCB has been prohibited for a long time, emissions from unidentified sites still occur. For example, recirculated waste paper used as raw material for new pulp was discovered downstream a paper mill. It is unclear how organic synthetic organic chemicals affect marine organisms but polychlorinated biphenyls (PCBs), for instance, are frequently found in fish liver, seal blubber, bird eggs, and human fat. Organochlorines have been associated with impaired reproductive ability in seals and whales. For instance, octachlorostyrene (OCSs) have been found in benthic organisms. OCS concentrations can be taken as an indication of incomplete combustion resulting in the accumulation of chlorinated hydrocarbons in marine organisms.
 
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Organometallic compounds such as tributyltin have been used extensively as antifouling agents and are now banned in many countries because of its effect known as ‘imposex’. Imposex refers to a change of sexual characteristics in invertebrates, female gastropods growing a penis, for instance. Compounds in alternative antifouling products form a special field of interest, since these compounds are especially applied to display their toxic effects in the marine environment. Their use is expected to increase in the near future due to the total ban on tributyltin-based antifouling chemicals by the ‘International Maritime Organisation’ (IMO) by 2003.
 
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It is now well established that there are anthropogenic chemicals released to the environment that can disrupt the endocrine systems of a wide range of wildlife species. The reproductive hormone-receptor systems appear to be especially vulnerable. Indeed, changes in sperm counts, genital tract malformations, infertility, an increased frequency of mammary, prostate and testicular tumours, feminisation of male individuals of diverse vertebrate species and altered reproductive behaviours, have all been reported (Sharpe & Skakkebaek, 1993; Colborn et al., 1996). With regard to environmental management, the problem of endocrine disrupting chemicals is extremely difficult to address. Basic research is required to strengthen the scientific foundation for risk assessment: e.g., baseline studies on endocrine dysfunction across classes of animals to reduce the uncertainty associated with species extrapolations (NSTC, 1996). An extensive list of chemicals which are thought to be capable of disrupting the reproductive endocrine systems of animals has been assembled. They fall into the following categories:
 
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Environmental oestrogens (oestrogen receptor mediated) (e.g., methoxychlor, bis¬phenolic compounds);
 
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Environmental antioestrogens (e.g., Dioxin, Endosulphan);
 
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Environmental antiandrogens (e.g., Vinclozolin, DDE, Kraft mill effluent);
 
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Toxicants that reduce steroid hormone levels (e.g., Fenarimol and other fungicides; endosulphan);
 
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Toxicants that affect reproduction primarily through effects on the CNS (e.g., dithio¬carbamate pesticides, methanol); and
 
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Other toxicants that affect hormonal status (e.g., cadmium, benzidine-based dyes).
 
  
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====Metals====
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Industrial development has altered, disturbed and destroyed coastal ecosystems, including sensitive habitats. Many important industrial centres are situated on estuaries and in the vicinity of urban areas and ports. Main industrial activities affecting coastal areas include iron ore smelting and processing, chemical and petrochemical industry (oil and gas storage and refining), paper mills, vehicle factories, ship building, power plants (coal, oil gas, nuclear energy) and food processing (including fish). Numerous pipelines, data and energy cables buried in the seabed create problems for other users (bottom trawl fisheries, marine aggregate extraction).
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Heavy metals are naturally occurring and do not degrade. They are not particularly toxic as the condensed free elements (except Hg vapour) but they are dangerous to living organisms in the form of cations and when bonded to short chains of atom carbon. In particular cations have a strong affinity for sulphur. For example, sulfhydril groups in enzymes attach themselves to cations or molecules and so the enzyme is blocked. They are a problem in the marine environment because they bio-accumulate in marine organisms and despite measures taken to combat pollution, they are still concentrating year after year. Pollution above background levels in the environment can cause serious effects. For instance, copper is a useful oligoelement bit in excess it affects trophic levels. As a free element, mercury has hundreds of applications, for example in electrical switches. Despite emissions of vapour from the industry have been curtailed, there are still releases from unregulated burning of fuel or wastes. This human source of pollutant is added and its atmospheric inputs rival volcanoes. The ultimate sink for metals and many organic compounds is the sediment. Processes involved include deposition and burial as heavy metals are retained by:
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Construction engineering activities often cause permanent destruction of habitats or decrease and fragmentation of habitats, due to land claim, coastal protection, extraction of bottom material, dumping and disposal.
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adsorption onto the surface of mineral particles
 
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complexation by molecules in organic particles
 
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precipitation reactions
 
  
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====Radioactive substances====
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Reclamation of [[salt marsh]]es and [[mangrove]]s has taken place for centuries almost everywhere in estuaries, intertidal bays and inlets throughout the world. The main impacts on marine ecosystems are: disturbance and removal of [[benthic]] organisms, damage to spawning areas for fish, alteration of the seabed, destabilisation of shallow banks and increased [[erosion]]. Severe beach erosion is a problem shared by many countries<ref>Luijendijk, A., Hagenaars, G., Ranasinghe, R., Baart, F., Donchyts, G. and Aarninkhof, S. 2018. The State of the World’s Beaches. Scientific reports 8:6641 DOI:10.1038/s41598-018-24630-6</ref>.
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Present day levels of radioactive substances found in coastal waters are the result of natural radioactivity (cosmic rays, earth crust), and possibly released radioactivity due to human activities such as oil exploration and combustion, phosphate production and use, land-based mining, managed discharges from nuclear power and reprocessing facilities, fallout from atmospheric nuclear weapons testing and accidents, medical diagnosis and therapy, and food conservation.
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The threat from industry and tourism infrastructure is still acute even if local and regional management plans help by slowing down the rate of construction. In several countries (e.g. Japan, Singapore, Hongkong and Dubai) artificial islands are built in the sea for urban extension, tourist resorts and airports. Changes to the shoreline have been extensive in recent decades and threats from rising sea levels and sinking landmasses have required the development of new coastal management strategies. For example, water storage schemes and managed retreat schemes along coastlines have been proposed and enacted as soft-engineering works, for dealing with long-term problems in an environmentally friendly and sustainable way (see also [[Climate adaptation policies for the coastal zone]]).
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The world's oceans have been a sink for radioactive waste from the production of nuclear weapons and electric power since 1944. Radioactive waste enters the ocean from nuclear weapon testing and the resulting atmospheric fallout, the releasing or dumping of wastes from nuclear fuel cycle systems, and nuclear accidents (for example Chernobyl in 1985). Dumping of high-level radioactive waste is no longer permitted in the ocean, but dumping of low-level wastes is still permitted. Low-level waste contains less radioactivity per gram than high-level waste. High-level wastes usually have longer half-lives. For example, one common high-level waste that is produced by spent nuclear fuel has a half-life of 24,100 years.
 
  
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====Oil and gas and offshore installations====
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===Dredging and dumping at sea===
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Oil is at the heart of the modern economy in providing a cheap source of energy and as a raw material for making plastics, etc. It is a mixture of hydrocarbons and up to 25% non-hydrocarbons such as sulphur, vanadium, and metals... Environmental impacts occur at all stages of oil and gas production and use. They result from prospecting activities (including seismic techniques), physical impact due to the installation of rigs, operational discharges when production starts, accidental and routine spills, and finally combustion. Nihoul & Ducrotoy (1994) have estimated the input of oil to the North Sea, due to the offshore industry, at 29% of the total input of oil. Offshore installations may disturb the environment through the placement of structures on the seabed, which disturb benthic organisms, acoustic disturbances and light emission. An increasing number of installations is currently reaching the end of their productive life and will need to be dismantled or removed throughout the world seas.
 
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Overall, coastal ecosystems remain largely affected by direct discharges of oil from offshore activities and illegal discharges from ships. Operational discharges consist of production water and drilling cuttings. Although the amount of oil discharged via production water is increasing as platforms are getting older, cuttings still account for 75% of the oil entering the sea as a result of normal operations. The effects on the marine environment have been extensively studied by national authorities as well as by the industry. Despite uncertainty about possible long-term effects, problems with oiled cuttings (drilling muds) are acknowledged. Effects in the vicinity of platforms are well known , in particular those on the macrobenthic invertebrates, which range from lethal to insignificant, depending on proximity. Spills of oil and the release of chemicals (i.e. lubricants) used during exploitation constitute an important source of chronic pollution to coastal seas. Even if accidental spills represent a relatively small source of oil, they directly affect birds and mammals and have devastative effects on local vulnerable economies. Shipping is a main source of oil slicks (chronic and accidental) showing no downward trend. Combustion of oil is the ultimate stage in the chain of production-use. Polycyclic aromatic hydrocarbons (PAHs) originate from various sources such flaring or engines, including on land. Nevertheless, their major sources are not the rivers but sources in the sea itself from platforms and ships (Laane et al., 1998). PAHs are volatile material which travel well airborne, showing the importance of the atmospheric pathway in the distribution of contaminants. Airborne pollutants are dissolved by rain and some are carried to the coast as dust particles or in solution from the atmosphere. The current knowledge about the dependence of the deposition velocity upon the particle size and about the processes controlling wet deposition fluxes, and the quality and completeness of the emission data are still inadequate for describing the environmental cycle and impact of such pollutants.
 
  
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==Conclusion===
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[[Image:DredgingMaasvlakte2.jpg |left|400px|thumb|Dredging for the construction of Rotterdam port extension Maasvlakte 2. Photo credit Port of Rotterdam.]]
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The effects of contaminants on coastal ecosystems are very difficult to assess. In the estimation of possible effects, the actual concentrations are compared with the levels that can cause effects. Results of laboratory experiments give only limited information in relation to the field situation, due to the complexity of natural systems and (in general) the co-occurrence of a multitude of contaminants in the field. Actual changes in the sea are often very difficult to discern from the large variability, which occurs naturally. Measurement of marine pollution using biological indicators provides information on the bio-availability of contaminants and the integration of the effects of multiple exposures and exposure over time. Multiple exposure is the combined action of all chemical contaminants. Even if the contaminants are present at concentrations too low to cause gross harmful effects, they can cause a suite of bio-chemical reactions in marine organisms generally called stress. Amongst the result of prolonged stress is the suppression of the immune system, thus increasing sensitivity towards the impact of infectious agents and parasites. Natural factors such as temperature extremes and fluctuations of salinity or anthropogenic activities, such as fisheries, can aggravate these reactions. A suite of bio-chemical reactions in marine organisms may occur as a response increasing sensitivity towards the impact of infectious agents and parasites.
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[[Dredging]] mainly causes physical disturbance and may result in the redistribution of contaminants through desorption from fine sediments. Offshore sand mining for beach nourishment and land reclamation and aggregate extraction for the construction industry causes temporary disturbance of benthic communities and in some cases permanent loss of habitats. Contaminants can be resuspended and remobilised from sediments and create new entries in the food web<ref>Eggleton, J. and Thomas, K. V. 2004. A review of factors affecting the release and bioavailability of contaminants during sediment disturbance events. Environment International 30: 973–980</ref><ref>Wenger, A. S., Harvey, E., Wilson, S., Rawson, C., Newman, S. J., Clarke, D., Saunders, B.J., Browne, N., Travers, M. J., Mcilwain, J. L., Erftemeijer, P. L. A., Hobbs, J. A., Mclean, D., Depczynski, M. and Evans, R. D. 2017. A critical analysis of the direct effects of dredging on fish. Fish and Fisheries 18: 967–985</ref>. Any increase in suspended matter will impede growth of filter feeding organisms (bivalves) and alter the burial capacity of benthos. It is well established that changes in substrate quality are synonymous to changes in the structure of [[benthic]] communities<ref>Hinchey, E.K., Schaffner, L.C., Hoar, C.C., Vogt, B.W. and Batte, L.P. 2006. Responses of estuarine benthic invertebrates to sediment burial: the importance of mobility and adaptation. Hydrobiologia 556: 85–98</ref><ref>Hendrick, V.J., Hutchison, Z.L. and Last, K.S. 2016. Sediment Burial Intolerance of Marine Macroinvertebrates. PLoS ONE 11(2): e0149114</ref>
  
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The bulk of material disposed in the sea comes from [[dredging]] of navigation channels. Sewage sludge dumping increases the fallout of organic material and associated contaminants to the seafloor. It can contribute to [[eutrophication]] in coastal waters, see [[What causes eutrophication?]] and other links in this article.
  
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The section on [[Water quality/pollution]] may be accessed via this link.
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Marine litter is derived from land-based and marine sources. It is found in large quantities on the coastal seabed, floating in the water column and on the shore. It is brought to the sea by rivers but originates also from activities at sea such as shipping, fishing and [[mariculture]] or recreation and tourism. About 80% of the material is plastic which is hardly degradable and provokes smothering. Entangling and drowning of [[biota]] (birds, mammals) may happen and inflict physical injury to animals (turtles) or even an obstruction of digestive system after ingestion of plastic objects. Once in the food-web, plastics release toxic substances<ref> Rochman, C. M., Hoh, E., Kurobe, T. and Teh, S. J. 2013. Ingested plastic transfers hazardous chemicals to fish and induces hepatic stress. Scientific reports: 3, 3263</ref><ref>Gallo, F., Fossi, C., Weber, R., Santillo, D., Sousa, J., Ingram, I., Nadal, A. and Romano, D. 2018. Marine litter plastics and microplastics and their toxic chemicals components: the need for urgent preventive measures. Environmental sciences Europe: 30(1), 13.</ref>. Containers or all sorts (bottles, boxes) will host alien species and help in the transportation of invasive species, see the article [[Non-native species invasions]] for an introduction to this topic.
  
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==Land use and coastal defences==
 
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===Land use and human populations===
 
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Some 60% of the world’s human population live close to the coast, within about 100 kilometers of the shore. This means that about 3.5 billion people rely heavily on marine habitats and resources for food, building materials, building sites, and agricultural and recreational areas and use coastal areas as a dumping ground for sewage, garbage, and toxic wastes. This proportion is expected to increase, along with growing urbanization, industrialization, and transportation, putting even greater pressure on the living and non-living resources of the coastal ocean. This section considers physical structures and land use modification in the coastal zone, and anticipated future developments (e.g. off-shore airports, wind-energy parks, land reclamation, etc.), due to an increase in human demography and increased use of coastal areas.
 
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The tremendous population increase puts a heavy burden on coastal zone management. The obvious global demand for proper guidelines to cope with these increasing pressures presents the science community with a major challenge, namely to supply scientific information on possible solutions, and on the predicted effects of the different measures. There is a need for systemic studies of the ecosystems associated with large coastal urban agglomerations. Growth in the so-called mega-cities adds to a tendency of people to concentrate in the coastal zone anyway. Clearly, this extends the range of impacts on the marine environment beyond traditional sewage and waste, adding things like increased risk of disasters, excessive noise levels and thermal pollution.
 
  
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Some of the increases in human population numbers are temporary and are due to migrations. Some of this migration towards the coast is temporary, albeit significant (Cook, 1996). For example, the Mediterranean coastal zone, which has a population of about 130 million, swells to 230 million for most of the summer, increasing transportation and pollution problems.
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==Land-sea flows ==
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===River runoff and load===
  
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===Coastal industries and constructions===
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[[Image:LookingDownTheNileFromTheAswanDam_JorgeLascar.jpg |left|500px|thumb| Looking down the Nile from the Aswan Dam. Photo credit Jorge Lascar [https://www.flickr.com/photos/jlascar/].]]
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Industrial development has altered, disturbed, and destroyed costal ecosystems, including sensitive habitats. Many important industrial centres are situated on estuaries and in the vicinity of urban areas and ports. Main industrial activities affecting coastal areas include metal smelting and processing, chemical, petrochemical (oil and gas storage and refining), paper mills, vehicle factories, ship building, power plants (coal, oil gas, nuclear energy), and food processing (including fish). Data and energy cables are numerous with similar effects to pipelines which are submerged in the seabed. This creates problems for other users (bottom trawl fisheries, marine aggregate extraction).
 
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Construction engineering activities very often cause permanent destruction of habitats or decreases in habitat size and their fragmentation, due to coastal protection, land reclamation, extraction of bottom material, dumping and disposal.
 
  
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Habitat infilling, in particular of salt marshes and mangroves, has taken place for centuries almost everywhere in estuaries, intertidal bays and inlets throughout the world. The main impacts on coastal ecosystems are disturbance and removal of benthic organisms, damage to sites as spawning areas for fish, alteration of seabed profiles, increase in instability of shallow banks and an increase in erosion. Severe beach erosion is a problem shared by many countries.
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Flow of fresh water and entrained materials to the [[coastal zone]] has been grossly altered by human activities<ref>Vorosmarty, C.J., Meybeck, M., Fekete, B., Sharma, K., Green, P. and Syvitski, J.P.M. 2003. Anthropogenic sediment retention: major global impact from registered river impoundments. Global and Planetary Change 39: 169–190.</ref>. In some arid regions where freshwater is diverted for irrigation, the discharge to the coastal zone has diminished to a small fraction of the natural flow. In other regions the issue is management of water, as the seasonal pattern of discharge has been greatly modified. Either water loss or alteration of the seasonality of discharge can have major impact on coastal ecosystems. Human activities have also altered the patterns of sediment discharge. In some regions increased soil erosion has occurred associated with human land use (especially agriculture) and has led to increases in sediment delivery. However, in most cases an overriding effect has been increased trapping of sediments in water reservoirs. Thus, some regions experience artificially elevated sediment discharge, whereas many others experience severe diminution. Either change can be detrimental to ecosystems acclimated to receive a particular level of sediment load. For example, severe erosion without sediment replacement may occur in systems poised to receive high sediment loads. For several large deltas such as the Nile and Colorado River deltas the sediment discharge to the coastal zone has diminished by more than 90% compared to the natural situation. By contrast, ecosystems such as [[coral reef]]s are generally acclimated to low sediment discharge, and large amounts of sediments can bury or otherwise damage reefs.  
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Threat from industry and tourism infrastructure is still acute even if local and regional management plans help slowing down the rate of construction. The construction of artificial islands is now well developed in Japan and in the Southern North Sea, for instance in the Netherlands for the installation of a future airport. This is a highly political issue. Changes to the shoreline have been extensive in recent decades and threats from rising sea levels and sinking landmasses have required new strategies to be developed. For example, water storage schemes and managed retreat schemes along coastlines have been proposed and enacted as soft-engineering works as environmentally friendly and sustainable methods of dealing with long-term problems.
 
  
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===Dredging and dumping at sea===
+
Human activities have generally led to increased discharges of [[pollutant]]s which affect [[Coastal pollution and impacts|water quality]]. Some countries have done better than others in effectively regulating and controlling these discharges.
−
Dredging mainly causes physical disturbance and may result in the redistribution of contamination through release from the sediment. Contaminants might be resuspended and remobilised from sediments and create new entries in food webs. Any increase in suspended matter will impede growth of filter feeding organisms (bivalves) and alter the burial capacity of benthos. It is well known that changes in substrate quality are synonymous to changes in the structure of benthic communities.
 
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The bulk of material eligible for dumping at sea comes from dredging operations from navigation channels, material removed in coastal engineering projects. beach nourishment, and reclamation and coastal marsh preservation. Sewage sludge dumping increases the fallout of organic material and associated contaminants to the seafloor. It can contribute to eutrophication in naturally nutrient rich coastal waters.
 
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Marine litter is derived from land-based and marine sources. It is found in large quantities on coastal seabed, floating in the water column and on the shore. It originates from many diverse activities such as shipping, fishing and mariculture or recreation and tourism. About 80% of the material is plastic which is non-degradable and provokes smothering. Entangling and drowning of biota (birds, mammals) may happen and inflict physical injury to animals (turtles) or even an obstruction of digestive system after ingestion of plastic objects. Once in the food-web, plastics release toxic substances. Containers or all sorts (bottles, boxes…) will host alien species and help in the transportation of invasive species.
 
  
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==Freshwater inputs==
+
===Groundwater discharge into the coastal waters===
 +
Although not as obvious as river discharge, continental ground waters also discharge directly into the sea. Like surface water, groundwater flows down-gradient. Therefore, groundwater flows directly into the ocean wherever a coastal aquifer is connected to the sea. Furthermore, artesian aquifers can extend for considerable distances from the shore, underneath the continental shelf. In some cases, these deeper aquifers may have fractures or other breaches in the overlying confining layers, allowing groundwater to flow into the sea. If polluted, groundwater flow into the sea will contribute to marine pollution. See for further details the article [[Submarine groundwater discharge and its influence on the coastal environment]].
  
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===River runoff and load===
+
===Seawater intrusion into the coastal aquifer===
−
Flow of fresh water and contained materials to the coastal zone has been grossly altered by human activities. In some arid regions, such as the Nile (Egypt) and Colorado (Mexico), where freshwater on land is a major resource limiting human activities, discharge has diminished to 10% or less of natural flow. In other regions the issue is management of water, with the seasonal pattern of discharge having been greatly modified. Either water loss or alteration of the seasonality of discharge can have major impact on coastal ecosystems. Human activities have also altered the patterns of sediment discharge. Although increased erosion has occurred associated with human land use (especially agriculture) and has led to increases in sediment delivery, a confounding effect has been increased trapping of sediments in water reservoirs. Thus, some regions experience artificially elevated sediment discharge; others experience severe diminution of discharge. To an ecosystem acclimated to receive a particular level of sediment load, either change can be detrimental. For example, severe erosion without sediment replacement may occur in systems (such as the Colorado River delta) poised to receive high sediment loads. By contrast, ecosystems such as coral reefs are generally acclimated to low sediment discharge, and large amounts of sediments can bury or otherwise damage reefs.  
+
Conversely, seawater intrusion in the coastal aquifer causes salinisation of fertile soil in low-lying parts of the inland coastal zone. These areas can therefore become unsuitable for agriculture, especially in arid regions, with considerable social and economic consequences. Coastal areas can also become less suitable for habitation due to upwelling of brackish water and salinisation of drinking water wells. These issues are exacerbated by climate change, on the one hand as a result of more frequent and longer dry periods and, on the other hand, as a result of sea level rise, which strengthens the salt water intrusion into the coastal aquifer<ref>Werner, A.D., Bakker, M., Post, V.E.A., Vandenbohede, A., Lu, C., Ataie-Ashtiani, B., Simmons, C.T. and Barry, D.A. 2013. Seawater intrusion processes, investigation and management: Recent advances and future challenges. Advances in Water Resources 51: 3–26</ref><ref>Oude Essink, G. H. P., van Baaren, E. S. and de Louw, P. G. B. 2010. Effects of climate change on coastal groundwater systems: A modeling study in the Netherlands. Water Resources Res. 46, W00F04, doi:10.1029/2009WR008719</ref>. For further details on this topic, see the article [[Groundwater management in low-lying coastal zones]].
−
Human activities have generally led to an increase discharges of pollutants which affect water quality. Some countries have done better than others in effectively regulating and controlling the discharges.
 
  
−
===Groundwater discharge into the coastal zone===
 
−
Although not as obvious as river discharge, continental ground waters also discharge directly into the sea. Like surface water, groundwater flows down-gradient. Therefore, groundwater flows directly into the ocean wherever a coastal aquifer is connected to the sea. Furthermore, artesian aquifers can extend for considerable distances from shore, underneath the continental shelf. In some cases, these deeper aquifers may have fractures or other breaches in the overlying confining layers, allowing groundwater to flow into the sea.
 
  
 
==Recreation and tourism==
 
==Recreation and tourism==
  
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Coastal areas provide recreation opportunities for local people and for tourists who travel the whole world. Tourism cause pressures on coastal ecosystems by excessive influx of visitors. People movements rely on transportation systems which range from pathways for walkers to landing strips for airports. Such movements at planetary level mean the wandering of pests, construction and building with associated pollution and eutrophication and disposal of litter and other waste in tourist areas. The paradox is that, most often, tourism will disturb and threaten local populations and wildlife and their habitats, which attracted them to the area in the first instance.
+
[[Coastal area]]s provide recreation opportunities for local people and for tourists who travel at present the whole world. Tourism causes pressures on coastal [[ecosystem]]s by excessive influx of visitors. People movements rely on transportation systems which range from pathways for walkers to landing strips for airports. These movements contribute to the wandering of pests, construction and building with associated [[pollution]] and [[eutrophication]] and disposal of litter and other waste in tourist areas. The paradox is that, most often, tourism will disturb and threaten local populations and wildlife and their habitats, which attracted them to the area in the first instance.
  
 
===Beaches, swimming, recreational boating===
 
===Beaches, swimming, recreational boating===
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Beaches are important areas for tourism. However, the increasing population and welfare push many areas to their sustainable limits, both from a tourist and environmental point of view. In beach tourism there are clear feed back mechanisms, nice beaches attract people, and too many tourists on the beach decrease the attractiveness. Tourism, a major source of income for many coastal communities, can have major effects on coastal environments unless scale and type of activities are controlled. Biodiversity reduction, resource depletion, and human health problems may result from the accumulated environmental effects. Setting maxima to tourist numbers is a proper managerial measure However, once these maxima are really reached, pressure to relax the restrictions increase. Clear definitions of maxima, and scientifically adopted calculation methods are necessary.
+
 
−
With the increasing welfare also the recreational boating increases, and in some countries harbours and marinas built primarily for recreational use by small boats may disturb more of the coastal zone than commercial and industrial use. The environmental impacts of marinas and small harbours depend on site location, design, construction methods, and ‘house¬keeping’. Careful site planning can help avoid or minimize many of the impacts.
+
[[Image:Benidorm_EnriqueDomingo_jpg.jpg |left|400px|thumb|Tourist resort Benidorm on the Spanish Mediterranean coast. Photo credit Enrique Domingo [https://www.flickr.com/photos/edomingo/].]]
 +
 
 +
Beaches are important areas for tourism. However, the increasing population and standard of living push many areas beyond their sustainable limits, both from a tourism and environmental point of view. In beach tourism there are clear feedback mechanisms: nice beaches attract people, and too many tourists on the beach decrease the attractiveness. Tourism, a major source of income for many coastal communities, can have major effects on coastal environments unless the scale and type of activities are controlled. [[Biodiversity]] reduction, resource depletion, and human health problems may result from the accumulated environmental effects. Setting maxima to tourist numbers is a proper managerial measure, however, once these maxima are reached, pressure to relax the restrictions increase. Clear definitions of maxima, and scientifically adopted calculation methods are still lacking.
 +
 
 +
Recreational boating increases with the increasing standard of living, and in some countries harbours and marinas built primarily for recreational use by small boats may disturb more of the [[coastal zone]] than commercial and industrial use. The environmental impacts of marinas and small harbours depend on site location, design, construction methods, and 'house-keeping'. Careful site planning can help avoid or minimize many of the impacts.
  
 
===Ecotourism===
 
===Ecotourism===
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Seabirds and marine mammals, particularly cetaceans, offer excellent opportunities for ecotourism in many parts of the world. Seabird colonies and seal rookeries are spectacular and increasingly popular places to visit. In many places around the world, whale watching trips are organized or specific advice is given by tourism organizations as to where and how whales can be observed from headlands and coastal promontories (Taylor, 1988). This rapidly growing interest for ecotourism has been reason for concern (De Groot, 1983; Coultier, 1984; Woehler et al., 1994). Subsequently, codes of ethics and best practice guidelines for ecotourism have been published and most of the major tourism organizations have formally declared to follow such guidelines.
+
Seabirds and marine mammals, particularly [[cetacean]]s, offer excellent opportunities for [[ecotourism]] in many parts of the world. Seabird colonies and seal rookeries are spectacular and increasingly popular places to visit. In many places around the world, whale watching trips are organized or specific advice is given by tourism organisations as to where and how whales can be observed from headlands and coastal promontories<ref>Taylor, L. 1988. Whale tourism: Look, don't touch. - Scanorama 58-66.</ref>. This rapidly growing interest for [[ecotourism]] has been reason for concern<ref>De Groot, R. S. 1983. Tourism and conservation in the Galapagos Islands. Biological Conservation. 26: 291-300.</ref><ref>Coultier, M. C. 1984. Whale tourism: Look, don't touch. In: Status and Conservation of the World's Seabirds. Croxall, J. P., Evans, P. G. H., and Schreiber, R. W, (ed). Techn. Publ., Cambridge, ICBP: 237-244.</ref><ref>Woehler, E. J., R.L.Penney, S.M.Creet and Burton, H. R. (1988). Impacts of human visitors on breeding success and long-term population trends in Adélie Penguins at Casey, Antarctica. Polar. Biol. 14: 269-274</ref>. Subsequently, codes of ethics and best practice guidelines for [[ecotourism]] have been published and most of the major tourism organisations have formally declared to follow such guidelines. This topic is further developed in [[Impact of tourism in coastal areas: Need of sustainable tourism strategy]].
 +
 
  
 
==Coastal hazards==
 
==Coastal hazards==
 +
The coastlines of many countries face high risks of damage from certain types of natural disasters. A major concern is death and property loss by winds and flooding by hurricanes or cyclones. Along many densely populated coastlines, the risks of natural disasters are being increased by population growth and unmanaged development projects, including residential urban development<ref name=N>Nicholls, R. J. et al. 2008. Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposure Estimates”, OECD Environment Working Papers, No. 1, OECD Publishing. [http://dx.doi.org/10.1787/011766488208]</ref>. Coastal natural disasters cut across all economic sectors. Wind or water damage from a cyclone (hurricane), flooding by tsunami, wreckage from an earthquake, or coastal erosion from storms can affect tourism, fishing, port operations, public works, transportation, housing and industry. For a more extensive discussion, see the article [[Shoreline management]].
  
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The coastlines of many countries face high risks of damage from certain types of natural disasters. The major concern is death and property loss by winds and waters of hurricanes or cyclones. Along many densely populated coastlines, the risks of natural disasters are being increased by population growth and unmanaged development projects, including residential urban development. Coastal natural disasters cut across all economic sectors. Wind or water damage from a cyclone (hurricane), inundation by tsunami, wreckage from an earthquake, or coastal erosion from storms can affect tourism, fishing, port operations, public works, trans¬portation, housing and industry.
+
Tropical cyclones (hurricanes) form over the warm oceans (at least 26<sup>o</sup> C) mainly over the western parts where no cold currents exist. Apart from wind and rain, a major impact is from the associated [[storm surge]] and storm waves. These have been responsible for major loss of life particularly in low lying densely populated coastal areas such as Bangladesh or China. [[Tsunami]]s are quite a different phenomenon and are often associated with subsea earth movements. However, their speed and height can cause extensive coastal destruction with little warning and some distance from their origin (see: [[Tsunami]]). Further details can be found in [[Extreme storms]] and [[Natural causes of coastal erosion]].
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Tropical cyclones (hurricanes) form over the warm oceans (at least 26 degrees C) mainly over the western parts where no cold currents exist. Apart from the wind and rain, a major impact is from the associated storm surge and storm waves. These have been responsible for major loss of lie particularly in low lying densely populated coastal areas such as Bangladesh or China. Tsunamis are quite a different phenomenon and are associated with sub sea earth movements. However, their speed and height can cause extensive coastal destruction with little warning and some distance from their origin.
 
  
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==Biodiversity – Invasive species==
 
  
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The composition and structure of the fauna, flora and habitats of coastal seas has been changing to an unusual rate in the last few decades, due to changes in the global climate and an increase in human activities. The unusual rapid rate of change, rather than the nature of the change itself, is the reason for the deterioration of many environments; over the last 50 years the rate and extent of this deterioration has been unprecedented, as were the consequences on biological diversity. The term ‘biodiversity’ is used by the Convention on Biological Diversity (1992) to refer to all aspects of variability evident within the living world, including diversity within and between individuals, populations, species, communities, and ecosystems. The term is commonly used loosely to refer to all species and habitats in some given area, or even on the Earth overall. In fact, it relates to environmental attributes, often species or species groups, which can be sampled and whose modification is supposed to reflect a change of biological diversity. What is important is the capacity of ecosystems to fulfil their role within the biosphere. The notion of functional diversity is useful in that it provides insight in the resilience of ecosystems and how changes affect them. There are many causes to losses of marine biodiversity, especially in the coastal waters of industrialized countries. Direct habitat destruction through the erection of engineering and drainage works which disturb the physical integrity of coastal and marine systems is the most drastic as the habitat itself is changed to a point where the ecosystem looses its identity and fulfils a completely different function as before. Poor fisheries management, including the uncontrolled exploitation of corals and molluscs and the by-catch of large numbers of non-target species in fisheries is another important aspect of the detrimental exploitation of marine living resources due to the lack of an integrated approach to coastal zone management, leading to impoverished functioning. As a consequence, the productivity of fisheries and such important ecosystems as mangroves and coral reefs has been depressed, and local human communities are suffering. In general, estuaries and salt marshes, mangrove forests, and sea grass beds near cities and towns are severely degraded worldwide with many species being threaten. The increasingly observed worldwide bleaching of corals could presage massive ecological changes for coral reefs and other marine ecosystems.  
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==Threats to [[Marine Biodiversity|biodiversity]]==
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 +
The composition and structure of the fauna, flora and habitats of coastal seas has been changing at an unusual rate in the last few decades, due to changes in the global climate, [[Non-native species invasions|invasive species]] and an increase in human activities. The unusual rapid rate of change, rather than the nature of the change itself, is the reason for the deterioration of many environments; over the last 50 years the rate and extent of this deterioration has been unprecedented, as were the consequences on biological diversity. The term biodiversity is used by the [http://www.biodiv.org/default.shtml Convention on Biological Diversity]  (1992) to refer to all aspects of variability evident within the living world, including diversity within and between individuals, populations, species, communities, and ecosystems. The term is commonly used loosely to refer to all species and habitats in some given area, or even on the Earth overall. In fact, it relates to environmental attributes, often species or species groups, which can be sampled and whose modification is supposed to reflect a change of biological diversity (see [[Measurements of biodiversity]])).
 +
 
 +
[[Image:AmericanJackknifeClam_jpmm.jpg |left|400px|thumb|The American jackknife clam ''Ensis Directus'' has colonized the beaches of NW Europe. Photo credit jpmm, [https://www.flickr.com/photos/jpmm/].]]
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 +
What primarily matters, is the capacity of ecosystems to fulfil their role within the biosphere. The notion of [[functional diversity]] is useful in that it provides insight into the [[Resilience and resistance|resilience]] of ecosystems and how changes affect them. There are many causes to losses of marine [[biodiversity]], especially in the coastal waters of industrialised countries. The most drastic loss is habitat destruction through the erection of engineering and drainage works, which disturb the physical integrity of coastal and marine systems, as the habitat itself is changed to a point where the ecosystem loses its identity and fulfils a completely different function as before. Poor fisheries management, including the uncontrolled exploitation of corals and molluscs and the by-catch of large numbers of non-target species in fisheries is another important aspect of the detrimental exploitation of marine living resources. This is further illustrated in the article [[Effects of fisheries on marine biodiversity]]. The underlying cause is the lack of an integrated approach to coastal zone management, leading to impoverished functioning<ref> Costanza R., Kemp W.M. and Boynton W.R. (1993). Predictability, Scale, and Biodiversity in Coastal and Estuarine Ecosystems - Implications for Management. Ambio: 22: 88-96.</ref>. As a consequence, the productivity of fisheries and such important ecosystems such as [[mangrove]]s and [[coral reef]]s has been depressed, with detrimental impact on local human communities. In general, estuaries and [[salt marsh]]es, mudflats, [[mangrove]] forests, and sea grass beds (such as [[Posidonia oceanica (Linnaeus) Delile|posidinia]]) near cities and towns are severely degraded worldwide with many species being threatened. The increasingly observed worldwide bleaching of corals could lead to massive ecological changes for [[coral reefs]] and other marine [[ecosystems]]. See also [[Marine Biodiversity]] and [[Threats to Coral Reefs: the Effects of Chemical Pollution]].
 +
 
  
 
==Conclusion==
 
==Conclusion==
 +
Living organisms play an essential role in [https://en.wikipedia.org/wiki/Marine_biogeochemical_cycles biogeochemical cycles] through coastal systems. They are themselves vulnerable to rapid changes which take place in the [[coastal zone]] due to [[anthropogenic]] activities, but changes in the structure of populations of organisms will in turn affect the geochemistry of the habitat, to a point where such cycles might become dysfunctional. The consequences of such changes taking place in coastal ecosystems may have consequences at global level leading to an unbalance in fluxes of energy and minerals at the interface between land and sea<ref>Crossland, C.J., Bairn, D. and Ducrotoy, J.P. 2005. The coastal zone: a domaine of global interactions. In: Crossland, C.J. (Ed.), Coastal Fluxes in the Anthropocene, Springer, Berlin, pp. 1-37</ref>. The dynamics of such systems are very high and complex meaning that conservation is not just concerned with fixing the coastline to its physical actual limits, fighting erosion and [[sea level rise]]. Because coastal systems are alive, they are able to cope with changes of any sorts, but what counts is more the rate of change than the nature of the change. What makes the anthropocene unique is the rapidity of changes inflicted by humans to natural systems. Threats of all sorts from human activities onto ecosystems are now well documented but action remains difficult and uncertain because of a lack of understanding of the scale and of the speed of observed changes. Notably, the variability of natural systems is difficult to include in any political reasoning which relies on the certainty of statements for decision making<ref> Costanza R. and Patten B.C. 1995. Defining and predicting sustainability. Ecological Economics 15: 193-196.</ref>. Through improving the scientific understanding of the performance of coastal ecosystems in terms of fluxes of energy and matter in relation to human impacts, [[Integrated Coastal Zone Management (ICZM)|integrated coastal management]] should become more able to predict the effects of measures taken and find adapted responses to fast evolving demands from society<ref> Yanagi T. and Ducrotoy J.P. 2003. Towards coastal zone management that ensures coexistence between people and nature in the 21st century. Marine Pollution Bulletin 47: 1-4.</ref><ref> Ducrotoy J.P. and Elliott M. 2006. Recent Developments in estuarine ecology and management. Marine Pollution Bulletin 53: 1-4.</ref>.
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==Related articles==
 +
:[[Integrated Coastal Zone Management (ICZM)]]
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:[[Pressures, impacts and policy responses in European coastal zones]]
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:[[Coastal pollution and impacts]]
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:[[Effects of fisheries on marine biodiversity]]
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:[[Coastal cities and sea level rise]]
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:[[Human causes of coastal erosion]]
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:[[Resilience and resistance]]
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Other articles in the [[:Category:Coastal and marine pollution]]
  
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Living organisms are an essential link in the turnover of biogeochemical cycles through costal systems. They are themselves vulnerable to rapid changes which take place in the coastal zone due to anthropogenic activities, but changes in the structure of populations of organisms will in turn affect the geochemistry of the habitat, to a point where such cycles might become dysfunctional. The consequences of such changes taking place in costal ecosystems may have consequences at global level leading to an unbalance in fluxes of energy and minerals at the interface between land and sea. The dynamics of such systems are very high and complex meaning that conservation is not just concerned with fixing the coast line to its physical actual limits, fighting erosion and sea-level rise. Because costal systems are alive, they are able to cope with changes of any sorts, but what counts is more the rate of change than the nature of the change. What makes the anthropocene unique is the rapidity of changes inflicted by humans to natural systems. Threats of all sorts from human activities onto ecosystems are now well documented but action remains difficult and uncertain because of a lack of understanding of the scale and of the speed of observed changes. Notably, the variability of natural systems is difficult to include in any political reasoning which relies on the certainty of statements for decision making. Through improving the scientific understanding of the performance of coastal ecosystems in terms of fluxes of energy and matter in relation to human impacts, integrated coastal management should become more able to predict the effects of measures taken and find adapted responses to fast evolving demands from society.
 
  
 
==References==
 
==References==
 
<references/>
 
<references/>
  
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==See also==
 
  
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==Further reading==
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EEA 2006. The changing faces of Europe's coastal areas. European Environmental Agency Report No 6/2006. ISSN 1725-9177 [https://www.eea.europa.eu/publications/eea_report_2006_6].
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Keller, D. R. and Golley, F. B. 1984. The philosophy of Ecology: From science to synthesis. - University of Georgia Press.
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Ducrotoy J.P., Elliott M. and De Jonge V. 2000. The North Sea. In: Shepard,C. (Ed.), Seas at the MIllenium, Elsevier, London.
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{{author
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|AuthorFullName=Ducrotoy, Jean-Paul
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{{Review
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|name=Job Dronkers
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''Author: Dr Jean-Paul Ducrotoy, University of Hull; EFMS (Eureopean Federation of Marine Science and Technology Societies), 2007. j-p.duc@wanadoo.fr''
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[[Category:Coastal protection]]
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[[Category:Coastal and marine pollution]]
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[[Category:Coastal and marine ecosystems]]
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[[Category:Integrated coastal zone management]]
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[[Category:Coastal and marine human activities and uses‏‎]]

Latest revision as of 18:28, 21 February 2024


This article presents an introduction to threats to the coastal zone that result from human activities and pressures. It discusses generic modifications to coastal ecosystems in relation to specific human activities and introduces the various threats resulting from poorly managed activities.


Climate change

A study by Halpern et al. (2019[1]) suggests that climate change is currently by far the most important stressor for ocean and coastal ecosystems. In this study the cumulative impact of 14 stressors related to human activities (including climate change, fishing, land-based pressures, and other commercial activities) on 21 different marine ecosystems globally was estimated for each of eleven years spanning 2003–2013. The increase of the estimated cumulative impact for the global ocean was estimated to be due for more than 90% to increasing sea surface temperature and acidity and the increase of the estimated cumulative impact for the coastal zones was estimated to be due for more than 80% to increasing sea surface temperature and sea level. Other results regarding threats resulting from climate change are dealt with elsewhere in the Coastal Wiki, see the page Climate change and the links and references therein.

Fisheries

The reader is referred to the separate pages Effects of fisheries on marine biodiversity and Mariculture. These articles discuss how and why ecosystems are at risk, while the human demand of resources from the sea is increasing, particularly in coastal areas.

Water quality/pollution

Oil pollution victim.

The separate pages Coastal pollution and impacts and Possible consequences of eutrophication discuss the way in which coastal and estuarine ecosystems have been, and still are, heavily influenced by anthropogenic pollution throughout the world. Examples of environmental issues include the enrichment of enclosed waters with organic matter leading to eutrophication and pollution by industrial chemicals and oil.


Land use and coastal defences

Land use and human populations

Some 40% of the world’s human population live not far from the coast, within about 100 kilometers of the shore [2]. This means that about 3 billion people rely to some extent on coastal and marine ecosystems, habitats and resources for food, building materials, building sites, and agricultural and recreational areas, while utilising coastal areas as a dumping ground for sewage, garbage, and toxic wastes. The pressure on the living and non-living resources of the coastal zone is expected to further increase, due to growing urbanization, industrialization, and transportation. This section considers physical structures and land use modification in the coastal zone, and anticipated future developments (e.g. off-shore airports, wind-energy parks, land reclamation, etc.), due to an increase in human demography and increased use of coastal areas. The tremendous population increase puts a heavy burden on the coastal zone requiring careful management. The obvious global demand for proper guidelines to cope with these increasing pressures presents the science community with a major challenge, namely to supply scientific information on possible solutions, and on the predicted effects of the different measures. There is a need for systemic studies of the ecosystems associated with large coastal urban agglomerations. Growth in the so-called mega-cities adds to a tendency of people to concentrate in the coastal zone, see the article Coastal cities and sea level rise. Clearly, this extends the range of impacts on the marine environment beyond traditional sewage and waste, adding things like increased risk of disasters, excessive noise levels and thermal.

Some of the increases in human population numbers are temporary and are due to seasonal migration. Some can be significant as for example in the Mediterranean coastal zone, which has a population of about 130 million swelling to 230 million for most of the summer, increasing transportation and pollution problems[3]. See also the articles Impacts originating from the tourism sector and Impact of tourism in coastal areas: Need of sustainable tourism strategy.

Coastal industries and constructions

The port of Le Havre at the mouth of the Seine River is surrounded by a nature reserve. Photo credit Port of Le Havre.

Industrial development has altered, disturbed and destroyed coastal ecosystems, including sensitive habitats. Many important industrial centres are situated on estuaries and in the vicinity of urban areas and ports. Main industrial activities affecting coastal areas include iron ore smelting and processing, chemical and petrochemical industry (oil and gas storage and refining), paper mills, vehicle factories, ship building, power plants (coal, oil gas, nuclear energy) and food processing (including fish). Numerous pipelines, data and energy cables buried in the seabed create problems for other users (bottom trawl fisheries, marine aggregate extraction). Construction engineering activities often cause permanent destruction of habitats or decrease and fragmentation of habitats, due to land claim, coastal protection, extraction of bottom material, dumping and disposal.

Reclamation of salt marshes and mangroves has taken place for centuries almost everywhere in estuaries, intertidal bays and inlets throughout the world. The main impacts on marine ecosystems are: disturbance and removal of benthic organisms, damage to spawning areas for fish, alteration of the seabed, destabilisation of shallow banks and increased erosion. Severe beach erosion is a problem shared by many countries[4]. The threat from industry and tourism infrastructure is still acute even if local and regional management plans help by slowing down the rate of construction. In several countries (e.g. Japan, Singapore, Hongkong and Dubai) artificial islands are built in the sea for urban extension, tourist resorts and airports. Changes to the shoreline have been extensive in recent decades and threats from rising sea levels and sinking landmasses have required the development of new coastal management strategies. For example, water storage schemes and managed retreat schemes along coastlines have been proposed and enacted as soft-engineering works, for dealing with long-term problems in an environmentally friendly and sustainable way (see also Climate adaptation policies for the coastal zone).

Dredging and dumping at sea

Dredging for the construction of Rotterdam port extension Maasvlakte 2. Photo credit Port of Rotterdam.

Dredging mainly causes physical disturbance and may result in the redistribution of contaminants through desorption from fine sediments. Offshore sand mining for beach nourishment and land reclamation and aggregate extraction for the construction industry causes temporary disturbance of benthic communities and in some cases permanent loss of habitats. Contaminants can be resuspended and remobilised from sediments and create new entries in the food web[5][6]. Any increase in suspended matter will impede growth of filter feeding organisms (bivalves) and alter the burial capacity of benthos. It is well established that changes in substrate quality are synonymous to changes in the structure of benthic communities[7][8]

The bulk of material disposed in the sea comes from dredging of navigation channels. Sewage sludge dumping increases the fallout of organic material and associated contaminants to the seafloor. It can contribute to eutrophication in coastal waters, see What causes eutrophication? and other links in this article.

Marine litter is derived from land-based and marine sources. It is found in large quantities on the coastal seabed, floating in the water column and on the shore. It is brought to the sea by rivers but originates also from activities at sea such as shipping, fishing and mariculture or recreation and tourism. About 80% of the material is plastic which is hardly degradable and provokes smothering. Entangling and drowning of biota (birds, mammals) may happen and inflict physical injury to animals (turtles) or even an obstruction of digestive system after ingestion of plastic objects. Once in the food-web, plastics release toxic substances[9][10]. Containers or all sorts (bottles, boxes) will host alien species and help in the transportation of invasive species, see the article Non-native species invasions for an introduction to this topic.


Land-sea flows

River runoff and load

Looking down the Nile from the Aswan Dam. Photo credit Jorge Lascar [3].

Flow of fresh water and entrained materials to the coastal zone has been grossly altered by human activities[11]. In some arid regions where freshwater is diverted for irrigation, the discharge to the coastal zone has diminished to a small fraction of the natural flow. In other regions the issue is management of water, as the seasonal pattern of discharge has been greatly modified. Either water loss or alteration of the seasonality of discharge can have major impact on coastal ecosystems. Human activities have also altered the patterns of sediment discharge. In some regions increased soil erosion has occurred associated with human land use (especially agriculture) and has led to increases in sediment delivery. However, in most cases an overriding effect has been increased trapping of sediments in water reservoirs. Thus, some regions experience artificially elevated sediment discharge, whereas many others experience severe diminution. Either change can be detrimental to ecosystems acclimated to receive a particular level of sediment load. For example, severe erosion without sediment replacement may occur in systems poised to receive high sediment loads. For several large deltas such as the Nile and Colorado River deltas the sediment discharge to the coastal zone has diminished by more than 90% compared to the natural situation. By contrast, ecosystems such as coral reefs are generally acclimated to low sediment discharge, and large amounts of sediments can bury or otherwise damage reefs.

Human activities have generally led to increased discharges of pollutants which affect water quality. Some countries have done better than others in effectively regulating and controlling these discharges.

Groundwater discharge into the coastal waters

Although not as obvious as river discharge, continental ground waters also discharge directly into the sea. Like surface water, groundwater flows down-gradient. Therefore, groundwater flows directly into the ocean wherever a coastal aquifer is connected to the sea. Furthermore, artesian aquifers can extend for considerable distances from the shore, underneath the continental shelf. In some cases, these deeper aquifers may have fractures or other breaches in the overlying confining layers, allowing groundwater to flow into the sea. If polluted, groundwater flow into the sea will contribute to marine pollution. See for further details the article Submarine groundwater discharge and its influence on the coastal environment.

Seawater intrusion into the coastal aquifer

Conversely, seawater intrusion in the coastal aquifer causes salinisation of fertile soil in low-lying parts of the inland coastal zone. These areas can therefore become unsuitable for agriculture, especially in arid regions, with considerable social and economic consequences. Coastal areas can also become less suitable for habitation due to upwelling of brackish water and salinisation of drinking water wells. These issues are exacerbated by climate change, on the one hand as a result of more frequent and longer dry periods and, on the other hand, as a result of sea level rise, which strengthens the salt water intrusion into the coastal aquifer[12][13]. For further details on this topic, see the article Groundwater management in low-lying coastal zones.


Recreation and tourism

Coastal areas provide recreation opportunities for local people and for tourists who travel at present the whole world. Tourism causes pressures on coastal ecosystems by excessive influx of visitors. People movements rely on transportation systems which range from pathways for walkers to landing strips for airports. These movements contribute to the wandering of pests, construction and building with associated pollution and eutrophication and disposal of litter and other waste in tourist areas. The paradox is that, most often, tourism will disturb and threaten local populations and wildlife and their habitats, which attracted them to the area in the first instance.

Beaches, swimming, recreational boating

Tourist resort Benidorm on the Spanish Mediterranean coast. Photo credit Enrique Domingo [4].

Beaches are important areas for tourism. However, the increasing population and standard of living push many areas beyond their sustainable limits, both from a tourism and environmental point of view. In beach tourism there are clear feedback mechanisms: nice beaches attract people, and too many tourists on the beach decrease the attractiveness. Tourism, a major source of income for many coastal communities, can have major effects on coastal environments unless the scale and type of activities are controlled. Biodiversity reduction, resource depletion, and human health problems may result from the accumulated environmental effects. Setting maxima to tourist numbers is a proper managerial measure, however, once these maxima are reached, pressure to relax the restrictions increase. Clear definitions of maxima, and scientifically adopted calculation methods are still lacking.

Recreational boating increases with the increasing standard of living, and in some countries harbours and marinas built primarily for recreational use by small boats may disturb more of the coastal zone than commercial and industrial use. The environmental impacts of marinas and small harbours depend on site location, design, construction methods, and 'house-keeping'. Careful site planning can help avoid or minimize many of the impacts.

Ecotourism

Seabirds and marine mammals, particularly cetaceans, offer excellent opportunities for ecotourism in many parts of the world. Seabird colonies and seal rookeries are spectacular and increasingly popular places to visit. In many places around the world, whale watching trips are organized or specific advice is given by tourism organisations as to where and how whales can be observed from headlands and coastal promontories[14]. This rapidly growing interest for ecotourism has been reason for concern[15][16][17]. Subsequently, codes of ethics and best practice guidelines for ecotourism have been published and most of the major tourism organisations have formally declared to follow such guidelines. This topic is further developed in Impact of tourism in coastal areas: Need of sustainable tourism strategy.


Coastal hazards

The coastlines of many countries face high risks of damage from certain types of natural disasters. A major concern is death and property loss by winds and flooding by hurricanes or cyclones. Along many densely populated coastlines, the risks of natural disasters are being increased by population growth and unmanaged development projects, including residential urban development[18]. Coastal natural disasters cut across all economic sectors. Wind or water damage from a cyclone (hurricane), flooding by tsunami, wreckage from an earthquake, or coastal erosion from storms can affect tourism, fishing, port operations, public works, transportation, housing and industry. For a more extensive discussion, see the article Shoreline management.

Tropical cyclones (hurricanes) form over the warm oceans (at least 26o C) mainly over the western parts where no cold currents exist. Apart from wind and rain, a major impact is from the associated storm surge and storm waves. These have been responsible for major loss of life particularly in low lying densely populated coastal areas such as Bangladesh or China. Tsunamis are quite a different phenomenon and are often associated with subsea earth movements. However, their speed and height can cause extensive coastal destruction with little warning and some distance from their origin (see: Tsunami). Further details can be found in Extreme storms and Natural causes of coastal erosion.


Threats to biodiversity

The composition and structure of the fauna, flora and habitats of coastal seas has been changing at an unusual rate in the last few decades, due to changes in the global climate, invasive species and an increase in human activities. The unusual rapid rate of change, rather than the nature of the change itself, is the reason for the deterioration of many environments; over the last 50 years the rate and extent of this deterioration has been unprecedented, as were the consequences on biological diversity. The term biodiversity is used by the Convention on Biological Diversity (1992) to refer to all aspects of variability evident within the living world, including diversity within and between individuals, populations, species, communities, and ecosystems. The term is commonly used loosely to refer to all species and habitats in some given area, or even on the Earth overall. In fact, it relates to environmental attributes, often species or species groups, which can be sampled and whose modification is supposed to reflect a change of biological diversity (see Measurements of biodiversity)).

The American jackknife clam Ensis Directus has colonized the beaches of NW Europe. Photo credit jpmm, [5].

What primarily matters, is the capacity of ecosystems to fulfil their role within the biosphere. The notion of functional diversity is useful in that it provides insight into the resilience of ecosystems and how changes affect them. There are many causes to losses of marine biodiversity, especially in the coastal waters of industrialised countries. The most drastic loss is habitat destruction through the erection of engineering and drainage works, which disturb the physical integrity of coastal and marine systems, as the habitat itself is changed to a point where the ecosystem loses its identity and fulfils a completely different function as before. Poor fisheries management, including the uncontrolled exploitation of corals and molluscs and the by-catch of large numbers of non-target species in fisheries is another important aspect of the detrimental exploitation of marine living resources. This is further illustrated in the article Effects of fisheries on marine biodiversity. The underlying cause is the lack of an integrated approach to coastal zone management, leading to impoverished functioning[19]. As a consequence, the productivity of fisheries and such important ecosystems such as mangroves and coral reefs has been depressed, with detrimental impact on local human communities. In general, estuaries and salt marshes, mudflats, mangrove forests, and sea grass beds (such as posidinia) near cities and towns are severely degraded worldwide with many species being threatened. The increasingly observed worldwide bleaching of corals could lead to massive ecological changes for coral reefs and other marine ecosystems. See also Marine Biodiversity and Threats to Coral Reefs: the Effects of Chemical Pollution.


Conclusion

Living organisms play an essential role in biogeochemical cycles through coastal systems. They are themselves vulnerable to rapid changes which take place in the coastal zone due to anthropogenic activities, but changes in the structure of populations of organisms will in turn affect the geochemistry of the habitat, to a point where such cycles might become dysfunctional. The consequences of such changes taking place in coastal ecosystems may have consequences at global level leading to an unbalance in fluxes of energy and minerals at the interface between land and sea[20]. The dynamics of such systems are very high and complex meaning that conservation is not just concerned with fixing the coastline to its physical actual limits, fighting erosion and sea level rise. Because coastal systems are alive, they are able to cope with changes of any sorts, but what counts is more the rate of change than the nature of the change. What makes the anthropocene unique is the rapidity of changes inflicted by humans to natural systems. Threats of all sorts from human activities onto ecosystems are now well documented but action remains difficult and uncertain because of a lack of understanding of the scale and of the speed of observed changes. Notably, the variability of natural systems is difficult to include in any political reasoning which relies on the certainty of statements for decision making[21]. Through improving the scientific understanding of the performance of coastal ecosystems in terms of fluxes of energy and matter in relation to human impacts, integrated coastal management should become more able to predict the effects of measures taken and find adapted responses to fast evolving demands from society[22][23].


Related articles

Integrated Coastal Zone Management (ICZM)
Pressures, impacts and policy responses in European coastal zones
Coastal pollution and impacts
Effects of fisheries on marine biodiversity
Coastal cities and sea level rise
Human causes of coastal erosion
Resilience and resistance

Other articles in the Category:Coastal and marine pollution


References

  1. ↑ Halpern, B.S., Frazier, M., Afflerbach, J., Lowndes, J.S., Micheli, F., O’Hara, C., Scarborough, C. and Selkoe, K.A. 2019. Recent pace of change in human impact on the world’s ocean. Scientific Reports 9: 11609
  2. ↑ Agardy, T. and Alder, J. (coordinating authors) 2005. Millennium Ecosystem Assessment Chapter 19 Coastal Systems. [1]
  3. ↑ Cook, P.J. 1996. Social trends and their impacts on the coastal zone and adjacent seas. Rep. 3, British Geological Survey.
  4. ↑ Luijendijk, A., Hagenaars, G., Ranasinghe, R., Baart, F., Donchyts, G. and Aarninkhof, S. 2018. The State of the World’s Beaches. Scientific reports 8:6641 DOI:10.1038/s41598-018-24630-6
  5. ↑ Eggleton, J. and Thomas, K. V. 2004. A review of factors affecting the release and bioavailability of contaminants during sediment disturbance events. Environment International 30: 973–980
  6. ↑ Wenger, A. S., Harvey, E., Wilson, S., Rawson, C., Newman, S. J., Clarke, D., Saunders, B.J., Browne, N., Travers, M. J., Mcilwain, J. L., Erftemeijer, P. L. A., Hobbs, J. A., Mclean, D., Depczynski, M. and Evans, R. D. 2017. A critical analysis of the direct effects of dredging on fish. Fish and Fisheries 18: 967–985
  7. ↑ Hinchey, E.K., Schaffner, L.C., Hoar, C.C., Vogt, B.W. and Batte, L.P. 2006. Responses of estuarine benthic invertebrates to sediment burial: the importance of mobility and adaptation. Hydrobiologia 556: 85–98
  8. ↑ Hendrick, V.J., Hutchison, Z.L. and Last, K.S. 2016. Sediment Burial Intolerance of Marine Macroinvertebrates. PLoS ONE 11(2): e0149114
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  12. ↑ Werner, A.D., Bakker, M., Post, V.E.A., Vandenbohede, A., Lu, C., Ataie-Ashtiani, B., Simmons, C.T. and Barry, D.A. 2013. Seawater intrusion processes, investigation and management: Recent advances and future challenges. Advances in Water Resources 51: 3–26
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  14. ↑ Taylor, L. 1988. Whale tourism: Look, don't touch. - Scanorama 58-66.
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  16. ↑ Coultier, M. C. 1984. Whale tourism: Look, don't touch. In: Status and Conservation of the World's Seabirds. Croxall, J. P., Evans, P. G. H., and Schreiber, R. W, (ed). Techn. Publ., Cambridge, ICBP: 237-244.
  17. ↑ Woehler, E. J., R.L.Penney, S.M.Creet and Burton, H. R. (1988). Impacts of human visitors on breeding success and long-term population trends in Adélie Penguins at Casey, Antarctica. Polar. Biol. 14: 269-274
  18. ↑ Nicholls, R. J. et al. 2008. Ranking Port Cities with High Exposure and Vulnerability to Climate Extremes: Exposure Estimates”, OECD Environment Working Papers, No. 1, OECD Publishing. [2]
  19. ↑ Costanza R., Kemp W.M. and Boynton W.R. (1993). Predictability, Scale, and Biodiversity in Coastal and Estuarine Ecosystems - Implications for Management. Ambio: 22: 88-96.
  20. ↑ Crossland, C.J., Bairn, D. and Ducrotoy, J.P. 2005. The coastal zone: a domaine of global interactions. In: Crossland, C.J. (Ed.), Coastal Fluxes in the Anthropocene, Springer, Berlin, pp. 1-37
  21. ↑ Costanza R. and Patten B.C. 1995. Defining and predicting sustainability. Ecological Economics 15: 193-196.
  22. ↑ Yanagi T. and Ducrotoy J.P. 2003. Towards coastal zone management that ensures coexistence between people and nature in the 21st century. Marine Pollution Bulletin 47: 1-4.
  23. ↑ Ducrotoy J.P. and Elliott M. 2006. Recent Developments in estuarine ecology and management. Marine Pollution Bulletin 53: 1-4.


Further reading

EEA 2006. The changing faces of Europe's coastal areas. European Environmental Agency Report No 6/2006. ISSN 1725-9177 [6].

Keller, D. R. and Golley, F. B. 1984. The philosophy of Ecology: From science to synthesis. - University of Georgia Press.

Ducrotoy J.P., Elliott M. and De Jonge V. 2000. The North Sea. In: Shepard,C. (Ed.), Seas at the MIllenium, Elsevier, London.


The main author of this article is Ducrotoy, Jean-Paul
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Citation: Ducrotoy, Jean-Paul (2024): Threats to the coastal zone. Available from http://www.coastalwiki.org/wiki/Threats_to_the_coastal_zone [accessed on 5-05-2024]




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