Search
deutsch
5 Coasts – A Vital Habitat Under Pressure

Coastal functions

Page:

PROVISIONING ECOSYSTEM SERVICES –
FISH, DIAMONDS, AND A WHOLE LOT MORE

Aquaculture
The term "aquaculture" covers several different forms of production. Traditionally the term was used for freshwater fish production such as carp farming. However, aquaculture also in­cludes mariculture, i.e. the cultivation of ­marine organisms at sea. There are now also hybrid forms in which marine animals are bred on land in special salt water tanks.

Protein for a growing world population

Since time immemorial humans have eaten fish and seafood from the oceans.
For thousands of years marine fish were only consumed near the coasts as it was not possible to transport fish inland over long distances. Over time, however, processes were developed that made it possible to preserve fish. At first, fish was preserved in salt. Later it was canned, which made it possible to transport it over great distances. Only when freezing technology was invented and allowed for the almost indefinite preservation of food did fish become a staple food even far away from coastal regions. Today fish is consumed in significant quantities worldwide and plays a major role in human protein supply. This is particularly true for West African countries such as Senegal or the small island states in the South Pacific where fish is one of the most important staple foods.
With the growth of the world population, the consumption of fish and seafood has increased vastly since the middle of the previous century. While in the 1960s the per capita consumption level stood at 9.9 kilograms, it passed the 20 kilograms mark for the first time in 2014, as the Food and Agriculture Organization of the United Nations (FAO) reports. This means that the consumption of fish and seafood doubled in just half a century. According to the United Nations, the world population will grow from 7 billion to approximately 9.5 billion people by 2050. More than an additional 2 billion people will need to be supplied with food and with protein in particular. Fish will contribute a significant proportion of this protein but it is obvious that wild caught fish cannot supply these additional quantities of protein if fish stocks are no longer to be subjected to overexploitation.
2.12 > The quantities of fish and seafood produced today are many times greater than they were in 1950. While aqua­culture was insignificant at first, it now provides almost half of the global production.
fig. 2.12: The quantities of fish and seafood produced today are many times greater than they were in 1950. While aqua­culture was insignificant at first, it now provides almost half of the global production. © after FAO
The degree to which coastal waters contribute to the supply of wild caught fish and seafood is difficult to quantify. Since the FAO’s global statistics do not differentiate between coastal waters and other waters, there are only rough estimates in the region of 90 per cent. In Europe, fisheries experts distinguish between coastal fishing, middle water fishing and distant water fishing, differen­tiating by size and levels of motorization of fishing vessels. Coastal fishing is dominated by smaller trawlers that are mostly 18 to 24 metres in length and have engine sizes of up to 300 HP. It overlaps with middle water fishing with trawlers that are mostly 18 to 32 metres long and have engine sizes of no more than 600 HP. Distant water fishing is carried out by even larger vessels up to and including factory ships with on-board facilities for processing and freezing caught fish.
Another definition of coastal fishing is that it is limited to the shelves – a term that describes the areas of relatively shallow water near the coastlines. The shelves slope gently to an average depth of 130 metres, ending at the break to the continental slope, which falls more steeply to greater depths. According to this definition, the fisheries in many of the shallow marginal seas, such as the East China Sea or the North Sea, would be considered coastal fisheries in their entirety, despite the fact that in purely legal terms a country’s coastal sea is limited to the 12 nautical mile zone.

Fish to feed the world

Aquaculture – the production of fish and other organisms in specialized installations – can play an important role in securing fish supplies in the future.
This form of production has grown significantly in recent years while the quantities of fish and seafood caught in the wild have hardly changed. In 2014 a total of 167.2 million tonnes of fish and seafood were consumed worldwide. Of these, 93.4 million tonnes were caught in the wild, 73.8 million tonnes originated from aquaculture production, and 26.7 million tonnes of the latter were produced at sea, exclu­sively in coastal waters. However, a much larger quantity, i.e. 47.1 million tonnes, now comes from land-based aquaculture installations. China accounted for the largest share of global aquaculture production at 60 per cent.
2.13 > China contributes 60 per cent of the global aquaculture production. Aquaculture installations such as the one shown here in Tolo Harbour near Hong Kong can be found in many of China's coastal regions.
fig. 2.13:  China contributes 60 per cent of the global aquaculture production. Aquaculture installations such as the one shown here in Tolo Harbour near Hong Kong can be found in many of China's coastal regions. © Yann Arthus-Bertrand/Getty Images
Aquaculture must be carried out in a sustainable way
if it is to offer hope for the future, as major mistakes have been made in recent decades. For example, in the 1990s hundreds of kilometres of mangrove forests along the coast of Indonesia were cut down in order to establish shrimp farms in the form of aquaculture monocultures. In many places, shrimp as well as fish continue to be pro­duced intensively and with a view to maximum yields. As a result they are more susceptible to diseases than their wild relatives and are preventively given antibiotics and other medication – with unforeseeable repercussions for the marine environment as well as for the end consumers. Another problem is the fact that the animals’ faeces lead to regional marine eutrophication, which considerably impairs water quality.
Meanwhile there has been something of a shift in thinking towards environmentally sound aquaculture. Mixed aquaculture systems in which several organisms are kept together and in which the faeces of one species serve as a food supply for other organisms are regarded as a promising alternative. Such systems are termed Inte­grated Multi-Trophic Aquaculture (IMTA). They allow for the combined production of, for example, fish, algae, molluscs and sea cucumbers. The fish are fed, while the sea cucumbers feed on excess fish feed and fish faeces. The algae, for their part, take up inorganic substances exuded by the fish. The molluscs, finally, filter particles from the water and keep the installation clean. The feed is thus put to optimum use while several different products can be harvested from a single installation.

Natural gas and oil extraction

Subsea deposits of natural gas and oil
are a significant provisioning service from an economic perspective. Although the bulk of both resources are extracted onshore, the proportion coming from the ocean (offshore gas and oil) is now substantial. Currently, offshore oil accounts for about 40 per cent and offshore gas for about 30 per cent of global extraction. It is not always possible to draw a hard and fast line between coastal and offshore drilling rigs, but one certainty is that offshore extraction began directly on the coast and then shifted ever further out to sea. One reason for this is the increasing exploitation of coastal deposits, but another factor is the technical progress that has made it possible to extract gas and oil from ever greater depths.
Offshore oil extraction began surprisingly early on. The first oil rigs in the sea were built back in 1896 in the Summerland field off the coast of Santa Barbara in California. In 1937 for the first time, oil was drilled from a platform two kilometres off the Gulf Coast of the United States. In the 1970s the relatively shallow North Sea with an average water depth of 90 metres was exploited as a natural gas and oil field. The first drilling platform was erected in 1971 in the Ekofisk oilfield on the Norwegian continental shelf. The Ekofisk field is 270 kilometres away from the Norwegian coast – in the middle of the North Sea, and thus a very long distance from the coast. Exactly as for fisheries, it is unclear how much of this sea area can reasonably be classified as coastal.
For example, in Ghana where the shelf is relatively slender and only extends 60 kilometres before dropping steeply into the deep sea, the large Jubilee oilfield is ­markedly closer to the coast. It is located on the steep slope at the edge of the continental shelf where the water depth is already around 1100 metres. The Iara oilfield off the Brazilian coast, only discovered in the year 2008, is in a similar situation. It is located around 230 kilometres off Rio de Janeiro at the foot of the continental slope at around 2200 metres depth.
It is now rare for oil drilling to take place directly on the coast within sight of land. With a few exceptions, most natural gas and oil fields today are found at water depths of several hundred metres. Among the exceptions are smaller and older natural gas or oil drilling rigs on the Dutch and German North Sea coast, which are just a few kilometres offshore.

Levelized electricity
generation costs

To determine how much it costs to generate electricity using a particular technology, generally the levelized cost of electricity generation is calculated. The levelized generation costs take account of all investment and operating costs and the costs of financing the technical plant. These are divided by the electricity output achieved over the plant’s lifetime, meaning that levelized electricity generation costs are usually stated in euros per megawatt-hour or euro cents per kilowatt-hour.

Harvesting energy at sea

Coastal waters have also recently begun to attract more interest for the generation of electricity from wind power. The number of offshore wind turbines has risen rapidly over the past few years. Global installed capacity trebled between 2011 and 2015 alone. The wind is stronger and more constant over the ocean than inland, and the electricity output from the open sea is distinctly higher than on the mainland. On land, markedly less land area is available in any case because minimum distances from buildings or conservation areas must be respected. By making use of special ships and new technologies, it has now become possible to install wind turbines at sea far more cheaply, quickly and in larger numbers than a few years ago.
Manufacturers of wind power plants have now even begun to manufacture rotor blades directly on the coast, in the vicinity of large offshore wind farms, so as to avoid the need for costly and cumbersome transportation on special trucks. This has given rise to new jobs in structurally weak coastal areas, especially in Great Britain. Nevertheless, because of the higher cost of constructing foundations for offshore turbines and the expense of deploying special ships, it is still more expensive to construct wind farms offshore than onshore at present. The costs of one kilowatt-hour of offshore electricity, known as the ­levelized costs of electricity generation, currently range from 12.8 to 14.2 euro cents depending on the site. In ­contrast, the onshore levelized electricity generation costs are between 5.3 and 9.6 euro cents.
The wind turbines in operation worldwide at the end of 2015 had a rated capacity of well over 12,000 megawatts, which is roughly equivalent to the capacity of 24 nuclear reactors. A good 5000 megawatts of this was ­attributable to the coastal regions of Great Britain alone. The next-highest ranking countries in terms of installed wind farm capacity are Germany, Denmark and China.
2.14 > Great Britain leads the expansion of offshore wind power. Germany connected several large wind farms to the power grid in 2015, taking second place in the worldwide rankings ahead of Denmark.
fig. 2.14: Great Britain leads the expansion of offshore wind power. Germany connected several large wind farms to the power grid in 2015, taking second place in the worldwide rankings ahead of Denmark. © Global Wind Energy Council (GWEC)
Paralleling the trend in natural gas and oil extraction, offshore wind turbines are no longer being installed directly adjacent to the coast but further out at sea. The world’s first offshore wind farm was commissioned in 1991 and consisted of eleven wind turbines just two kilo­metres off the Danish island of Lolland at a water depth of two to four metres. Today, offshore wind farms are constructed at average water depths of 27.1 metres and an average distance of 43.3 kilometres from the coast. A substantial distance is observed particularly in Germany and the Netherlands because the Wadden Sea along their coasts is an important resting site for migrating birds. Furthermore, wind speeds are higher at greater distances from land. German wind farms are an average of 52.6 kilometres from the mainland, as opposed to an average of 9.4 kilometres from the coast for those around Great ­Britain. The world’s largest wind farm, with 175 wind ­turbines over an area of 100 square kilometres, is the ­London Array wind farm in the outer Thames estuary on the east coast of England.
Wind power is not the only renewable form of energy that can be utilized in coastal waters. Additional forms are:
  • wave power,
  • tidal power,
  • marine current power,
  • salinity gradient power (osmotic power),
  • ocean thermal energy conversion (power generated from temperature differentials at different ocean depths).
The role of these forms of energy is still relatively minor in comparison to wind power. In recent years facilities harvesting wave power have been taken into commission, but have not yet proven economically viable to operate. Generally they consist of research and development projects.
Also still in its infancy is the technology for generating power from differentials in salinity. Commissioned in 2009, a small power plant in Norway was the first of its kind in the world to feed electricity into the public grid. In terms of its developmental status, however, it is considered a prototype. The technology for ocean thermal energy conversion is likewise at prototype status. In 2015 a pilot plant was commissioned off the coast of Hawaii with a capacity of 105 kilowatts. It now supplies 120 house­holds with electricity.
In comparison, the use of tidal and marine current power plants to harvest energy is a fully developed technology. An example is the La Rance tidal power plant near the French city of Saint-Malo, which has been in operation ­since 1966. All told, only a few larger plants exist worldwide because they are extremely elaborate to construct, since dams and barrages with large turbines have to be installed in order to harness energy from tides and currents.
2.15 > So far the majority of the world’s wind farms have been constructed at distances of up to 40 kilometres from the coast and water depths up to 20 metres. In the meantime, offshore technology is so fully developed that installations can now be planned and built at far greater distances offshore. Proposed sites are located 120 kilometres offshore in extreme cases.
fig. 2.15: So far the majority of the world’s wind farms have been constructed at distances of up to 40 kilometres from the coast and water depths up to 20 metres. In the meantime, offshore technology is so fully developed that installations can now be planned and built at far greater distances offshore. Proposed sites are located 120 kilometres offshore in extreme cases. © European Wind Energy Association (EWEA)

fig. 2.16: Particularly on the west coast of Africa, as here in the Western Sahara but also in Morocco, sand is extracted on a large scale close to the coast. This is exported worldwide for use as building sand and for other purposes. © Veronique de Viguerie/Getty Images

2.16 > Particularly on the west coast of Africa, as here in the Western Sahara but also in Morocco, sand is extracted on a large scale close to the coast. This is exported worldwide for use as building sand and for other purposes.

Valuable minerals

Another resource supplied by coasts are mineral raw materials, particularly sand and gravel which are used in concrete production, as filling sand on building sites, or for hydraulic filling to create new port or industrial sites on the coast. Well-known examples are the hydraulic fills that created land for the expansion of Hong Kong airport, the artificial Palm Islands off Dubai, or the new container terminal in Rotterdam, Europe’s largest port. Sand and gravel are either dredged from the sea floor using suction dredgers or extracted onshore – especially by demolishing dunes. Exact quantities are very difficult to estimate because data are not recorded centrally. Nonetheless, sand and gravel extraction and the export of both resources are considered to be a lucrative business.
For example, the island city-state of Singapore constantly consumes large quantities of sand in order to expand the city’s area by means of hydraulic filling. As a result of these activities, the area of the former British colony has expanded by a good 20 per cent since the 1950s. Singapore has much of the sand shipped in from very long distances. Many other countries also import sand. Sand from Australia is in particular demand because of its extremely hard, resilient and angular grains. On the one hand, this sand is good for concrete production be­cause the grains adhere well to one another as the cement sets. On the other hand, the sand is used in ­industry as a blasting abrasive for sanding or smoothing other materials. According to data from the Australian Bureau of Statistics (ABS), Australia exports sand, gravel and stones valued at 5.5 to 8.5 million euros per month. It is extracted both from the coast and from inland sites.

Natural gold-panning effect

A more uncommon type of mineral resource are mineral placers: shallow deposits of metal or phosphorus compounds which form along coasts near to river estuaries. They come about through a kind of natural gold-panning effect: particles ranging from light to heavy are transported from the hinterland by flowing river water. In and around the estuary these are deposited in the shallow water off the coast. If the ocean swell is strong enough, the lighter particles are washed away while the heavier ones are buried more deeply in the sea floor. Over the course of millennia this process results in the formation of deposits several metres thick, which can be recovered by mining. Mineral placers can contain metals like iron, gold, platinum, tin or rare earth metals. At present, extraction is confined to especially valuable mineral placers only, such as those containing gold, platinum or diamonds. The latter are found along the coast of Namibia, where there is a strip just a few kilometres wide with a relatively shallow ocean depth of up to 150 metres. Ever since it was discovered in the late 1950s that large quantities of diamonds occurred in this part of the ocean, it has been the site of intensive offshore mining. Initially the sediments were only harvested by divers with large suction tubes. Currently extraction is taking place at depths of 90 down to 150 metres on an industrial scale using special ships. The area was divided up into several concessions in which different consortiums of firms operate. Today some two-thirds of all Namibian diamonds are obtained from the sea.
The fact that the sea floor off Namibia happens to be so rich in diamonds is thanks to the Orange River. The frontier river between Namibia and South Africa washed the gemstones from their region of origin, South Africa’s volcanic areas, into the sea. Over time, sea currents transported the sediment containing the diamonds northwards from the Namibian coast, where they concentrated in the sea floor as a result of the gold-panning effect.
Currently it is under discussion whether the mineral placers here containing phosphate compounds should also be extracted in future. These would be sold as fertilizers. Because the sea level has risen by around 130 metres ­since the last Ice Age, today these phosphate deposits lie deep below the waterline.

Resources from hydrothermal vents

Another type of valuable minerals that are likely to be recovered from the sea in future are the massive sulphides. These are found around hydrothermal vents on the sea floor, either at active undersea volcanoes or at plate boundaries where two continental plates are diverging.
Massive sulphides originate when cold seawater penetrates through fissures several kilometres deep in the sea floor. Around magma chambers at this depth, the water heats to temperatures of more than 400 degrees Celsius and dissolves sulphides, i.e. sulphur compounds, as well as minerals containing metals from the sur­rounding rock. Because it has been heated the mineralized water rises very quickly and shoots back into the sea. As soon as it mixes with the cold seawater, the minerals form a precipitate that settles around the plume in the form of massive ore deposits.
Normally the active volcanic sites are in the middle of the oceans and far from land. One exception is the Bismarck Sea off New Guinea, where a plate boundary is found just 30 kilometres from the coast. Known as the ­Solwara-1 field, its deposits are easily accessible by ship and contain copper, zinc, lead, gold and silver as well as numerous important trace metals like indium, germanium, tellurium and selenium. But despite the proximity to the coast, the water depth is around 1600 metres because the sea floor drops away steeply at this point. The Canadian mining company Nautilus Minerals has long been planning the extraction of the valuable ore deposits and has already had heavy underwater mining machinery built. In addition, a production ship is currently under construction. So far the commencement of mining activities has been repeatedly postponed because the financing of the project was not adequately secured or no agreement could be reached between Nautilus Minerals and the Papua New Guinea authorities. When the mining of massive ­sulphides might begin therefore remains to be seen. >
Page: