Living on Coast in Harmony with Natural Processes

Living on Coast in Harmony with Natural Processes: History

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Subjects: Green & Sustainable Science & Technology

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The coastal zone is a fascinating place that comprises the interface between sea and land. This interface, which is both very dynamic and sensitive, has been affected by strong urban and industrial pressures, and an increase in both traffic and recreational uses, leading to the deterioration of natural habitats and the growing instability of residential areas. Added to this disruption is ongoing climate change, which will lead to rising sea levels and increased wave action. Another problem we are increasingly concerned about is ocean pollution, which has been one of the main causes of threats to deep-water coral reef areas. The main sources of pollution include oil spills and offshore oil drilling. The effects of pollution caused by oil spills can not only seriously affect the global environmental balance of our planet but can also, on a different scale, seriously affect the economy of countries whose main resources depend heavily on the sea. Wave energy has the potential to alleviate the world's dependence on depleting fossil energy resources. With regard to coastal protection, the development of ecological solutions to preserve ecosystems and address coastal processes as an alternative to traditional coastal protection structures (seawalls, groins and breakwaters) is becoming increasingly important. These structures, generally referred to as passive measures, are usually built to alter the effects of sea waves, currents and the movement of sand along the coastline, with the aim of protecting beaches, ports and harbors.

climate change
rising sea level
ocean pollution
coastal protection

1. Introduction—Coastal and Ocean Concerns

According to the EPA [1], people living in coastal areas will be strongly affected by ongoing climate change, as it will lead to rising sea levels, consequent flooding, and intensified wave action. As a result, coastal erosion and the amount of sediment in transit will increase [2].

While efforts are being made to reduce the causes and mitigate the effects of global climate change, they remain critical in coastal areas. In fact, many of the adaptation strategies implemented in coastal areas have proven to be inadequate or ineffective, and several coastal habitats are being affected [2,3,4,5,6,7,8,9].

More coastal flooding, more tropical storms, less biodiversity, fewer glaciers, and millions of people living in coastal regions at risk, are the broad strokes of the report by the UN’s Intergovernmental Panel on Climate Change (IPCC) [10].

Rising sea waters have been accelerated by the loss of ice from the Antarctic and Greenland ice caps. In Antarctica, ice loss was three times greater between 2007 and 2016 than it had been between 1997 and 2006, according to the report by IPCC [10]; in Greenland, it was twice as great. This acceleration in Antarctica could “potentially lead to a rise in sea levels of several meters in a few centuries”.

This report also shows the advantages of acting—and doing so as quickly as possible—and, at the same time, the drastic consequences of delayed action. The researchers make it clear that the oceans “critically depend on ambitious and urgent emission reductions”, coordinated with measures to adapt to the damage already done.

Meanwhile, coastal habitats face increasing risks around the world as a result of human action, both locally and contributing to ongoing climate change. Given the important contributions of coastal habitats to coastal protection, fish production and the economy of local communities, the degradation of these habitats represents huge cultural and economic losses, as well as an increased risk of coastal flooding [11,12,13,14,15,16,17]. A coherent review on the valuation and quantification of coastal ecosystems and services, including human-induced and climate change impacts on the monetary value of ecosystems, is provided by Mehvar et al. [18].

The risks of flooding in coastal areas, especially in low-land areas, due to climate action are high. Extreme sea levels can occur during storms, which can lead to coastal flooding in the absence of sufficient coastal protection. According to the European Environmental Agency (EEA), a 10 cm rise in sea level typically increases the frequency of flooding to a given height by a factor of approximately three [19]. Situations like those documented in Figure 1 are common in many regions of the globe. Future floods may not be (and hopefully will not be) as devastating as this one, but if current projections are maintained, small-scale events may become a daily issue for some coastal communities by the end of the century [20].

Figure 1. On climate change—coastal flooding—Hurricane Sandy flooded the New Jersey shoreline in 2012 [20] (accessed 23 August 2023).

Most assessments of coastal vulnerability due to climate change focus primarily on the impacts of sea level rise. However, many other studies have shown that changes in storms and wave climate have the potential to cause more significant coastal impacts than those related to sea level rise.

According to Gomes et al. [21], there is clear evidence that extratropical systems in the North Atlantic basin have decreased overall in the last 50–100 years, but on the other hand, there has been an increase in the frequency of really strong storms.

Still with regard to the North Atlantic, it is known that global climate change has led to changes in the trajectories of extratropical storms with considerable regional changes associated with this change, although without a global intensification of extratropical cyclonicity [22].

As reported in [23,24], the occurrences recorded in January 2013 and throughout the winter of 2013/2014, due to the combination of an intense polar vortex and a strong jet stream in the North Atlantic, caused a set of low-pressure systems that crossed the Atlantic and reached the coasts of western Europe.

According to several recent studies, the intensity and frequency of storms is likely to increase with potential implications for the wave climate on the European Atlantic coast [25,26,27,28,29]. There was a very significant linear growth in the number of occurrences from the mid-1990s onwards [3].

To understand how the current climate could change in the future, different greenhouse gas emissions scenarios were developed based on assumptions about future demographic changes, economic development, and technological advances. The scenarios cover a wide range of the main demographic, economic, and technological drivers of future greenhouse gas and sulfur emissions, which include anthropogenic emissions of carbon dioxide, methane, nitrous oxide, sulfur dioxide, carbon monoxide, and nitrogen oxides, among others [30].

Each of the four scenarios developed represents a specific quantitative interpretation. Based on these emission ranges, concentration trajectories are similar until about 2025–2030 and then diverge sharply. This figure shows ensemble-mean changes and uncertainties for 2021–2040 (near-term), 2041–2060 (mid-term), and the 2081–2100 (long-term), relative to 1995–2014 (present day) and the approximation to 1850–1900 (pre-industrial) [31].

Therefore, according to the Intergovernmental Panel on Climate Change [32,33], current environmental conditions will most likely tend to worsen with the increase in temperature, with a more significant increase in the number and intensity of storms being expected from the second half of the current century.

According to NOAA’s 2021 Annual Climate Report, “the combined temperature of land and ocean has increased at an average rate of 0.08 °C per decade since 1880; however, the average rate of increase since 1981 has been twice as fast: 0.18 °C per decade”. These values are in line with the IPCC graph and are corroborated by [34], which reports a global average rate of temperature increase of 0.19 °C per decade from 1979 to 2022, with a 95% confidence interval ±0.02 °C [34]. Somewhere in the literature, it is also stated that 2012–2021 was the warmest decade on record since the beginning of thermometer-based observations.

If the current trend continues, this means an average temperature increase of ~1.4 °C by 2100, which may correspond to the most likely value or slightly above that estimated by SSP2-4.5, according to IPCC.

According to [2], analyses of long-term instrumental data for the European Atlantic coast also revealed significant wave height increasing trends of about 1–2% per year. This trend is an important factor that should be taken into account in future coastal management plans and emergency evacuation plans.

Also, in accordance with [2], 50% of the most intense hurricanes in memory and 80% of hurricanes with a diameter greater than around 1300 m have occurred in the Atlantic this century. Global climate change is expected to worsen this trend. The continued population increase along coastal zones exacerbates the importance of the effects of possible coastal flooding resulting from storms.

There are many impacts associated with the global warming trend that have become evident in recent years. Arctic summer sea ice coverage has declined dramatically, and the ocean’s heat content has increased. According to ESA [35], “sea level has risen globally by around 15 cm during the 20th century and is currently rising more than twice as fast at a rate of 3.6 mm per year (between 2006–2015)”.

According to [36], many plant and animal species are changing the geographical distribution and timing of their life cycles due to changes in warming and precipitation. In addition to the effects on the climate, the oceans are absorbing part of the excess CO₂ from the atmosphere, leading to changes in their chemical composition and causing their acidification.

Sea level rise can have dramatic consequences for natural coastal systems. Among the most important biogeophysical effects are, although they do not occur simultaneously and with similar effects in different regions [37,38]:

Inundation, flood, and storm damage;
Erosion and sediment deficits;
Wetland loss (and change);
Rising water tables/impeded drainage;
Saltwater intrusion;
Biological effects.

Despite the appeals regularly made at successive meetings and protocols since 1992 with The United Nations Framework Convention on Climate Change (UNFCCC) adopted during the Rio de Janeiro Earth Summit in 1992, the commitments assumed so far are not enough and the forecasts continue to be dramatic, especially from the mid-21st century onwards.

An important consequence of global warming is the rise in sea levels through two mechanisms: (1) the melting of polar ice caps, which adds water to the oceans, and (2) the expansion of ocean water as it warms, leading to an increase in its volume and the consequent average rise in sea level.

Another problem we face with growing concerns is ocean pollution, as it has been a major cause of threats to coral reef areas in deep waters. According to the Ocean Pollution Guide [39], around 20 billion tons of waste are dumped into the sea every year, often without any prior processing. Marine plastic pollution is also an important source of pollution in itself, especially microplastic pollution, in addition to acting as a concentration vector of other ocean chemical pollutants [40].

Among the main sources of marine pollution are oil spills and oil exploration offshore as well. It is well known that oceans have been, are and will continue to be an alternative source of fossil fuels. Oil explorations had a large increase on land in the nineteenth century. However, since the early twentieth century, with the depletion of some oil and gas reserves onshore, petroleum companies have been on a constant lookout for the availability of offshore resources [41,42].

In addition to the oil platforms, offshore oil and gas explorations require permanent support from ships to transport products, materials, and equipment. Although technology has improved, natural disasters, operational discharges, and accidents that cause oil spills occur frequently and can be disastrous in less favorable weather conditions [43]. However, it should be noted that accidental spills from tankers in 1985 amounted to around 400,000 tons and have declined to around 100,000 tons per year in more recent years.

Figure 2 shows the coast of Galicia, Northern Spain, polluted after the accident of the oil tanker Prestige that occurred in the Atlantic Ocean in November 2002, when the vessel sank leaking around 30,000 tons of fuel oil [44].

Figure 2. Photo of a Galician beach (Spain) after the Prestige tanker accident on 13 November 2002 [44].

According to [45], the oil tanker spills decreased consistently since the 1970s both in the number of oil spills and the amount of oil lost. The average number of spills per year in the 1970s was approximately 79 and decreased by over 90% to 6 in the 2010s. Moreover, the amount of oil spilled in the 2010s was 164 000 tons, which represents a 95% reduction since the 1970s.

However, although less frequent and in smaller amounts, the impacts of accidents involving oil tankers cannot be overlooked, as oil spills kill marine flora and fauna. While cetaceans migrate from their areas, the small fish, corals, and plants on the ocean floor suffer the most [46].

2. On the Climate Change—Current Status and the Future

Climate change is defined as any change in weather averaged over time due to natural variability or because of human activity. Currently, there are many issues that we face in our daily lives as a result of ongoing climate change. When it comes to oceans and coastal areas, we are at risk from a range of climate change-related hazards and processes. The top 10 issues that, if left unchecked, will lead to deep changes in Earth’s climate, biophysical changes in coastal environments and ecosystems, and our current way of life include:

Global warming from fossil fuels.
Melting ice caps and sea level rise.
Ocean pollution.
Ocean acidification.
Groundwater salinity.
Biodiversity loss.
Severe storms.
Loss of climate regulation.
Overfishing.
Poor governance.

It is neither appropriate nor possible to address all concerns surrounding these topics in sufficient depth here. However, the need for an in-depth discussion on these topics and the implementation of appropriate guidelines to keep our ecosystems in balance is clear.

3. On the Ocean Pollution—Detection, Control, and Cleanup

The total amount of hydrocarbons annually introduced into the marine environment is estimated at around 3.2 million tons, being the pollution resulting from ship operations and oil tanker accidents, including oil exploration platforms, estimated at approximately 1.5 million tons. Accidental oil tanker spills represent an annual contribution of approximately 400 000 tons, most of which occur during routine loading, unloading, and provisioning operations [25].

After the occurrence and detection of an oil spill at sea, it is important to implement measures to mitigate its negative impacts. SAR remote sensing methods are generally the best suited for detecting oil spills after they occur [54,55,56,57]. However, mathematical modeling is a very powerful tool for managing an oil spill accident, namely, to monitor the evolution of the oil slick taking into account the spreading and weathering processes, such as evaporation, vertical dispersion, emulsification, and viscosity changes, and also for determining preventive measures [44,57].

By simulating the oil slick evolution, numerical models together with SAR satellite data and GIS technology (using SAR satellite data processing and adding it to ArcGIS Pro map, for example) make it possible to reorient the evolution of the oil slick at sea and redefine its characteristics, such as area and thickness, at detection points. In fact, whenever an accident of this type occurs, answers are essentially sought for the following questions:

What is the position of the oil slick?
Where is it heading?
What is the state of the product?

A management support tool developed for accidental hydrocarbon spills in the Atlantic coastal waters off the Iberian Peninsula is described in [44]. It is mainly composed of three interconnected modules: (1) the basic information for data organization and handling, which is organized into four different sets; (2) the SAR satellite data processing analysis and GIS visualization; and (3) the modelling tools for the spreading and weathering processes simulation and spilled oil transport.

This computational structure was used to study the hydrodynamics at the time of the N/T Prestige accident occurred on 13 November 2002, and the evolution of the fuel oil mass spilled during the 15 days following the accident. For the description of the spilled oil slick transport, both a Lagrangian and a Eulerian mathematical formulation can be used. Figure 3 compares the simulation results of the spilled fuel oil mass using both descriptions. For modelling details and possible comparisons with the trajectories of deriving systems, see [44].

Figure 3. Lagrangian versus Eulerian mathematical descriptions. Fuel oil mass evolution on the sea surface after the N/T Prestige accident on 22, 24, and 26 November 2002.

A numerical oil slick model that simulates the transport and weathering of an oil spill that occurred in a coastal area, coupled with a 3D hydrodynamic model, is presented in [58]. A three-dimensional model considering a Eulerian description of the oil slick evolution [59] was applied in an enclosed water body, in order to take immediate action upon the occurrence of such an accident. A two-dimensional oil spill model using a Eulerian description for oil slick evolution was used in [60] to investigate oil spread in a limited area in the southern part of the Korean Peninsula. A three-dimensional mathematical oil spill model that uses a Lagrangian formulation to assess the risk of oil spills along the coast of an island is presented in [61]. More recently, numerical simulation of the drift and spread of oil slicks in marine environments using the hydrodynamic model TELEMAC-2D and a stochastic approach based on a two-dimensional advection–diffusion equation transformed into a Lagrangian representation is presented in [62].

According to the WEO [63], more than a quarter of the current oil and gas supply is produced offshore and it is estimated that by 2040 the amount of energy-related offshore activity will increase.

Therefore, we must be prepared for any emergency related to an oil spill and cleaning up oil from the sea. Procedures must be adopted that include applications of marine monitoring tools to mitigate potential impacts arising from the exploration and transport of petroleum products.

Currently, the most common methods of cleaning the sea after an oil spill are oil booms, skimmers, sorbents, burning, dispersants, and other much safer methods such as hot water washing or high-pressure water washing, bioremediation, and natural recovery.

Oil booms, also called “Containment Bars”, are the most common and popular equipment used in oil cleaning due to their simpler design and easier execution. The mechanism consists of enclosing the oil in a smaller area, preventing it from spreading further [64]. Figure 4 shows a type of oil bloom installed for representational purposes.

Figure 4. Oil Boom oil spill—composed of three parts: freeboard, skirt, and cable or chain [64]. Surface-controlled net for collecting the crude and oil adsorbing elements.

The skimmers or oil scoops are fitted onto boats and serve to extract the floating oil or greasy contaminants bounded by the oil booms; basically, they suck all greasy products spread over the confined surface of the water in the oil booms. The use of sorbents aims to adsorb or absorb liquids. It is a common and easy process of oil cleaning using, in general, peat, straw, and hay.

The burning method is the most efficient oil cleaning method as it can efficiently remove 98% of the total spilled oil. Dispersants are used when oil cannot be confined to booms and are intended to initiate the disintegration of the oil.

Other methods often employed for safer cleanups of offshore oil spills are hot water washing or high-pressure water washing, bioremediation, and natural recovery.

This entry is adapted from the peer-reviewed paper 10.3390/jmse11112113

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