WOR 5 Coasts – A Vital Habitat Under Pressure | 2017

Coastal functions


Coasts develop as holiday destinations

The world’s coasts are more than just trading zones, military border zones or sources of food supply. Very early in human history, people also discovered the significance of coasts as a place of recreation, health and a wellspring of strength for the soul. In 414 BC the Greek philosopher Euripides wrote: “The sea washes away and cleanses ­every human stain.” He was referring particularly to the coastal zone where the elements of earth, water and wind meet. The Romans embraced the idea of the ocean’s healing power. Strolls and banquets on the beach were integral to the cultivated leisure of the aristocracy. For this sweet idleness, the Romans used the word “otium”. They did not bathe in the sea, however. Instead they ­established numerous thermal baths at warm volcanic springs, like those on the Italian island of Ischia which are still in use today.
2.7 > Back in 1907 the promenade at Brighton was already popular with visitors, and the appeal of the English coastal resort for tourists remains undiminished to this day.
fig. 2.7:  Back in 1907 the promenade at Brighton was already popular with visitors, and the appeal of the English coastal resort for tourists remains undiminished to this day.<br /> © Interfoto/Mary Evans
fig. 2.8: The Hamburg shipowner Albert Ballin is acknowledged as the inventor of the cruise. In order to make better use of his passenger ships’ capacity in winter, from 1891 he began to offer cruise trips to cities all around the Mediterranean. © ull- stein bild – The Estate of Emil Bieber/Klaus Niermann

2.8 > The Hamburg shipowner Albert Ballin is acknowledged as the inventor of the cruise. In order to make better use of his passenger ships’ capacity in winter, from 1891 he began to offer cruise trips to cities all around the Mediterranean.
In the Middle Ages, humans became more estranged from the ocean again. Despite the spread of trade between coasts, some of which were very long distances apart, the oceans were generally considered to be menacing and inhabited by monsters. The beaches of the Mediterranean were thought of as forbidding, pirate-infested territory. It was not until the seventeenth century that the ocean reverted to being a yearned-after location. One influence in this direction was the English scholar Robert Burton, whose book The Anatomy of Melancholy published in 1621 was a collection of historical and philosophical reflections from the previous 2000 years on the theme of melancholy. In this treatise he praised summer retreats beside the sea and advised those suffering from melan­choly to observe the restless ocean.
The English gentry, or country nobility, also began to appreciate the importance of physical exercise in the fresh air. In the town of Scarborough on the east coast of England, acidic mineral springs were discovered in 1626. The population credited the water with healing effects, and the fame of the springs quickly spread throughout the country. By the beginning of the eighteenth century the town was developing into an established spa resort, ­although at first it was normally only members of the gentry who could afford to stay there.
The English doctor Richard Russell prompted a surge in popularity with his studies on the healing effect of sea water. In 1747 he settled in the seaside resort of Brighton on the south coast of England. He wrote that people with glandular illnesses would recover more quickly thanks to healing baths in the cool water, and that women suffering from physical weakness also recovered quickly. Countless people now began to travel, particularly from London, to convalesce in Brighton and it developed into one of the most popular coastal resorts in the country – no longer just for the nobility but also for members of the well-off middle classes.
Germany’s first seaside resort, Heiligendamm on the German Baltic coast, was founded in 1793. In the decades that followed, many other coastal locations in Europe ­turned into seaside resorts.
An entirely different kind of coastal tourism was launched by the Hamburg shipowner Albert Ballin in the 1890s: the passenger cruise, visiting a series of ports of call along the coasts. Ballin had been operating passenger ships on the route between North America and Europe for some long time. Many of those who set off in Ballin’s ships were emigrating. Since the ships were not sufficiently used in the winter period, Ballin came up with the idea of filling the ships’ capacity by offering pleasure trips to warmer regions. On 22 January 1891 the passenger ship Augusta Victoria put out to sea from Cuxhaven on the world’s first pleasure cruise. It was at sea for 57 days, 22 hours and 3 minutes, and headed for regions which sounded very exotic to most northern Europeans in those days: Egypt, the island of Malta or the port of Lisbon.

What coastlines can do

From a human perspective, coastal habitats perform a ­range of other functions, the “ecosystem services”, which can be categorized as follows:
  • Supporting ecosystem services, which are necessary for the provision of all other ecosystem services and include, for example, primary production and nutrient cycles;
  • Regulating ecosystem services, which provide benefits and utility from the regulating effects of coastal waters and their ecosystems;
  • Provisioning ecosystem services, which encompass products and goods for human use on the one hand and spaces provided by the sea on the other;
  • Cultural ecosystem services, which include a range of functions and utility serving the nonmaterial well-being of humans.
The concept of ecosystem services is well-suited to a systematic categorization and analysis of the multitude of services provided by coastal regions that are of material or nonmaterial benefit to humankind. However, such ana­lyses often do not address societal issues such as, for ex­ample, the question of equitable distribution or of which societal groups benefit from services. In this respect a ­critical view must be taken of one-sided, purely economic assessments of ecosystem services that do not embrace sociocultural or ethical considerations.
Where habitats are considered solely with respect to the services they provide to humankind, all too often no consideration is given to the fact that every habitat can be of value whether it is utilized by people or not. Environmental ethicists speak of “non-utility value”. This includes the existence value ascribed by humans to beings such as corals or habitats such as mangrove forests regardless of whether they will ever be able to utilize or experience ­these organisms or habitats. The existence value is based purely on a sense of joy as to the fact that these species or habitats exist at all.
The non-utility value also includes the bequest value which is based on the human desire to pass on natural assets to future generations in as intact a condition as possible. Non-utility values, which are categorized as cultural ecosystem services, are not easily measured. Assessments of non-utility values must also obtain, for example, knowledge held by local communities and other stakeholders – such as knowledge of special religious or spiritual signi­ficance of a habitat for the population. Only if such knowledge is taken into account can the value of a habitat be measured.

fig. 2.9:Productive preciousness: Diatoms are among the most important primary producers. The beauty of their cell walls only becomes evident under high magnification. Microscopic samples such as these were popular souvenirs a century ago, especially among diplomats. © Watson & Sons, London

2.9 > Productive preciousness: Diatoms are among the most important primary producers. The beauty of their cell walls only becomes evident under high magnification. Microscopic samples such as these were popular souvenirs a century ago, especially among diplomats.

Small but productive

Primary production, the production of biomass by plants and microorganisms, is the basis of all marine life as well as the most important ecosystem service. Plants and microorganisms mostly obtain their energy from photosynthesis or from certain chemical compounds; they produce high-energy substances such as glucose (sugar). The most important primary producers in the oceans include microscopically small components of marine phytoplankton such as diatoms, coccolithophorid algae and cyanobacteria (formerly called blue algae). Since phytoplankton is dependent on sunlight, it lives exclusively in surface ocean waters. Similar to terrestrial plants, in addition to sunlight the phytoplankton needs nutrients such as phosphorus and nitrogen compounds. These are primarily transported by rivers into the sea. As coastal waters offer both sufficient sunlight and nutrients, they are among the particularly productive oceanic regions. This productivity also gives rise to particularly abundant fish stocks since tiny crustaceans as well as larvae of fish and bivalves feed on phytoplankton, and they in turn are a food source for fish.
However, not all the nutrients are derived from rivers. In the upwelling systems, for example, nutrient-rich cold water rises from the depths of the oceans. Such systems can be found along the coasts of Chile, California, Mauritania and Namibia. Their primary production is ­correspondingly high. Similar to the productive coastal waters, these upwelling systems give rise to particularly abundant fish stocks.

Seagrass meadows
Seagrass meadows are special habitats found on sandy soils in shallow waters and mudflats. While seaweeds use holdfasts to attach to rocks, seagrass sets roots with which it stabilizes sandy marine sediments. Numerous organisms, such as smaller seaweeds or molluscs, can gain hold among the plants, often making seagrass meadows particularly biodiverse habitats. Moreover, seagrass is an important food source for many species of marine fauna and waterfowl.

But the level of primary production in coastal waters is not only dependent on the nutrient quantities transported by currents and rivers but also on the intensity of water mixing. This mixing of water masses results in major variations in nutrient concentrations between ­different coastal segments and water depths. In the Bay of Bengal, where the Ganges and Brahmaputra form a large delta and transport a great amount of nutrients from the Himalaya Highlands into the ocean, the level of primary production changes with the monsoon. In the summer, when the moist monsoon winds blow, there is a lot of precipitation which strongly dilutes the coastal waters, thus reducing their nutrient concentration.
Another one of the world’s particularly productive coastal regions is the South China Sea. This is because the Pearl River reaches the sea west of Hong Kong. It has ­several tributaries and forms South China’s largest river system. Its watershed basin measures approximately 452,000 square kilometres, which is roughly equivalent to the land area of Sweden. Corresponding to the size of the river system, it transports enormous quantities of nutrients into the South China Sea.

Extra Info Transformations of a key nutrient – the nitrogen cycle

The coast – a wastewater treatment plant

Coastal waters play an important role in purifying effluent and removing pollutants conveyed by rivers and sewers and deposited from the atmosphere. They thus have a regulating function and are vital for nutrient decomposi­tion, especially for the breakdown of nitrogen compounds. Plants need nutrients, notably nitrogen and phosphorus, in order to grow. To increase the productivity of arable land and achieve higher yields, these nutrients are applied to agricultural land in the form of slurry, sewage sludge or artificial fertiliser.
In intensive agriculture regions high levels of nutrients enter the soil as the crop plants grown tend to not fully take up the fertilizers applied. Rainwater washes ­these surplus nutrients into the groundwater, streams and rivers, and ultimately into the sea. The phosphorus and nitrogen compounds also increase algal growth. Where there is an oversupply of nutrients, algal growth can be so rapid that it results in pronounced algal blooms. The more abundant the algae, the more intensive is their decomposition by oxygen-consuming microorganisms in deeper water layers. This phenomenon is called eutrophication. In extreme cases it results in zones devoid of oxygen in which fish, crustaceans and molluscs can no longer survive.
With the intensification of farming, the number of oxygen-deficient or oxygen-depleted zones in coastal waters has sharply increased since the 1960s, especially in the northern hemisphere. Worldwide some 400 coastal areas are regularly affected by oxygen-deficiency; these areas cover a total of 245,000 square kilo­metres, which is roughly equivalent to the size of Romania. Oxygen-deficiency primarily affects coastal waters in Europe, along the eastern US seaboard, the Gulf of Mexico and increasingly also in China. The decomposition of nitrogen compounds is of particular significance in this context as these enter the seas in large quantities. Fertilizers, slurry and excrements mostly contain nitrogen in the form of ammonium ions (NH4+). In the presence of oxygen, ammonium oxidizes to nitrate. In environmental waters, microorganisms (denitrifying bacteria) convert the nitrate to gaseous nitrogen (N2) in a process called denitrification. Algae cannot use gaseous nitrogen as a plant nutrient. Thanks to denitrification, coastal waters to a certain degree function as the ocean’s wastewater treatment plants.
2.11 > The estuary of the Salak River on the island of Borneo is dominated by mangrove forests. They protect the coastline from hurricanes and storm surges.
fig. 2.11: The estuary of the Salak River on the island of Borneo is dominated by mangrove forests. They protect the coastline from hurricanes and storm surges. © Timothy Laman/Getty Images
However, if the quantities of nutrients entering the ocean are too large, these can no longer be fully decom­posed, thus leading to eutrophication.
The various plant communities occurring in coastal waters contribute significantly to the elimination of nutrients. These communities include, in particular, mangroves and seagrass meadows, the roots of which take up large quantities of nutrients in the same manner as terrestrial plants. Nutrient decomposition is further enhanced by the numerous organisms living in the seabed, such as molluscs or worms. Millions upon millions of these organisms live buried in the seabed. Their several centimetres long burrows give many sediments the appearance of sponges. Compared to the normally solid and dense sediment which water can only enter through the spaces between the sediment grains, the numerous burrows enlarge the surface area on which microorganisms can engage in ­denitrification. This significantly enhances the effluent purification function of coastal waters.
Coastal waters also have a regulating function when it comes to the decomposition or neutralization of pollutants such as persistent chemical compounds or heavy metals transported into the coastal seas by rivers or the atmosphere. The dilution of pollutants is one of the processes, while they are also sequestered into the sediment through the activities of sediment-dwelling organisms which, for example, filter pollutants from the water with their feed and subsequently deposit them in the sediment with their faeces. While the pollutants are not removed from the environment in this manner, their sequestration into the sediment prevents other marine organisms from ingesting them. Ultimately these processes also prevent pollutants from being ingested by humans through the food chain.

Taming the ocean’s force

Coastal habitats such as dunes, coral reefs and mangroves perform a key protective function for humans as they are able to break winds and swells, thus regulating the ­oceans’ physical forces. For example, Abidjan, the Ivory Coast town, is protected by seaward dunes, as are the Dutch city of Amsterdam, the Nigerian city of Lagos or Durban in South Africa.
The importance of mangrove forests for coastal protection has become particularly evident in recent years. Tropical storms can produce tidal waves of up to 7 metres in height. As a study conducted by British researchers has shown, mangroves provide outstanding protection against such storm surges and hurricanes. Using mathematical modelling the scientists were able to demonstrate that a one kilometre wide mangrove forest can be expected to reduce surface wind energy by 75 per cent and wave height by up to half a metre. Considering that natural mangrove forests can be many square kilometres in size, they offer significant protection, for example along the southern coastline of Florida where they cover an area of roughly 2000 square kilometres. However, mangrove forests along many tropical coasts have suffered large-­scale destruction over many years. In Indonesia, for instance, they were removed to make space for aquaculture. Colombia has lost almost 20 per cent of its mangrove forests – here they fell victim to timber extraction. Studies have shown that the damage caused by the 2004 tsunami in the Indian Ocean, and especially the damage caused along the Indonesian coast, would not have been anywhere near as severe if the mangrove forests had not been cut down over many years. >