- > WOR 5 focusses on the coastal habitat and how increasing pressures on this habitat can be addressed in the future. Although the feasibility of influencing the occurrence of natural disasters such as tsunamis and earthquakes is negligible, it is possible for people to act against climate change. Today, a wide variety of approaches and ideas have already been proposed for the responsible use and enhanced protection of coastal regions in the future. In this respect, however, it is important not only to take account of the diverse stakeholder interests that exist today, but also to take action in pursuit of the sustainable stewardship of our coasts in the future.
Coasts – A Vital Habitat Under Pressure
Coasts are a special habitat. They are the transitional zone between land and sea, are influenced by both spheres, and are extraordinarily polymorphous. Whereas Brittany’s northern French coastline is rocky and gouged by innumerable inlets, the high dunes of the Namib Desert on the coast of Namibia extend panoramically to meet the Atlantic, while differently again, the low-lying coast of Siberia consists of permafrost, i.e. ground frozen to a depth of several metres.
The variety of coastal landscapes is matched by the diversity of services they render to humankind. They provide important transport routes and industrial sites; they are favoured destinations for recreation and tourism, and they are sources of mineral and fossil resources. For that reason, coasts have always been especially popular sites for human settlement. The populations of many coastal areas have been growing for decades. According to United Nations estimates, around 2.8 billion people today live within 100 kilometres of the coast. Of the world’s 20 megacities, i.e. cities with more than 10 million inhabitants, 13 are in near-coastal locations. It is widely expected that the urbanization of coastal areas will continue to advance in the next few years. It is estimated that in 2060 around 1.4 billion people will be living in low elevation coastal zones at elevations of no more than 10 metres above sea level.
In relation to terrestrial land mass as a whole, coasts are ultimately just a narrow strip where the land meets the sea. When people colonize this coastal strip, in many cases they give no thought to the fact that it is subject to constant natural change – and that over the course of time these changes can also destroy areas of human settlement. Changes of this kind happen on different time scales: those caused by plate tectonics occur over millions of years, permanently changing the form of the Earth’s surface and the continents; temperatures swing between glacial and interglacial periods on a cycle lasting tens of thousands of years – while changes in recent centuries have largely come about due to the impacts of human settlement. Over relatively short periods of geological time, it is mainly fluctuations in sea level that dramatically affect the morphology of the coasts.
- During glacial periods, large volumes of water are sequestered on land in the form of ice and snow. The sea level is lowered because very little water flows back from the land into the ocean. During the last glacial period around 20,000 years ago, it was around 120 metres lower than it is today. Many areas that are submerged today were dry land during that period, and the land mass protruding above the waterline was a total of 20 million square kilometres larger than it is today. For around 6000 years the sea level has barely changed. Due to human-induced global warming, however, for the last several decades it has begun to rise more markedly once again, by an average of 3 millimetres per year at the last count. There is an impending risk that entire island nations or low-lying coastal areas will be inundated in future – in Bangladesh, for example, which lies only slightly above the present-day sea level.
Depending on coastal morphology, widely diverse habitats have developed over time. Where rivers carry large quantities of nutrients and sediment into coastal waters, today – depending on climatic conditions and the prevailing currents – there are expansive river deltas with wide sandbanks, tidal mudflats or salt marshes. Such coastal areas are often especially productive and abundant in fish, thanks to the heavy discharge of nutrients. One of the rivers that carry particularly high levels of sediment into the sea is the Mississippi, around the mouth of which a large delta has developed. The record-holder is the Ganges, though: every year it carries around 3.2 billion tonnes of material into the sea. In contrast, other shorelines are more barren and rocky, like the limestone coast of Croatia from which very few nutrients find their way into the sea. Likewise, tropical coral reefs are found mainly at sites where nutrients and sediment barely flow into the sea from the land.
- Today the coastal areas of the world are intensively used. They supply the bulk of the world’s wild-caught fish. In fact, 90 per cent of global fishery takes place in coastal waters. Another use of great economic significance is the drilling of natural gas and oil in coastal areas. Although the bulk of both resources is still extracted onshore, the proportion coming from the sea (offshore gas and oil) is substantial. Currently offshore oil accounts for about 40 per cent and offshore gas for about 30 per cent of total global extraction.
In the past few years, coastal waters have become increasingly attractive sites for the harnessing of wind energy to generate electricity. The number of offshore wind turbines has increased markedly, and by the end of 2015 the combined capacity of all the offshore wind turbines in operation worldwide was at least 12,000 megawatts, which roughly equates to the capacity of 24 nuclear reactors. Another resource supplied by coasts are mineral raw materials, particularly sand and gravel, which are used in concrete manufacturing, as filling sand on building sites, or for hydraulic filling to create new port or industrial sites on the coast. The largest sand-mining area is located on the coast of Morocco. Dunes are being excavated and removed on a massive scale with wheel loaders, so that the coast in some regions resembles a lunar landscape.
In many places, human use of the coasts is exceeding their carrying capacity. The sources of pressure on these habitats are multifarious. High levels of nutrients are discharged into the sea from untreated effluents, from intensively fertilized agricultural lands or from aquaculture. This leads to eutrophication and to severe algal blooms. Pollutants from industrial processes that seep into coastal waters also pose a threat. These include heavy-metal compounds or persistent chemical substances that accumulate in the food chain and can give rise to illnesses like cancer. An example of these are polyfluorinated compounds, which have been in use for years now for everyday products like outdoor clothing or pan coatings. Likewise, the plastic waste that finds its way into the sea by many different routes raises a problem that is currently a matter of serious debate. Marine animals and seabirds swallow pieces of this plastic and die. Furthermore, the plastic decays into microscopically small fragments, microplastics, which are now in evidence in all the world’s oceans. Scientific studies are currently investigating to what extent animals ingest them and how dangerous they are. Global plastics production has been increasing for years. Between 2005 and 2015 alone it rose by over 90 million tonnes, from 230 to more than 320 million tonnes. >