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  • Ella Coulson

Climate Change and Human Impacts on Coastal Ecosystems

BY ELLA COULSON


Image source: gorsh13/Getty Images


A coastal ecosystem is a habitat on the border of land and sea that serves as a home for a variety of plants and other organisms. Its shallow water allows for ample access to sunlight, stimulating plant growth and allowing these ecosystems to serve as the core of oceanic primary productivity. Coastal ecosystems aid in the regulation of carbon in the ocean and provide shelter for a diverse group of organisms. Additionally, they offer sources of food and income for populations and protect coastal infrastructure by mitigating storm surges and flooding. Unfortunately, climate change and human impacts continue to threaten the health and stability of these habitats, leading to issues of coral bleaching, habitat loss, infrastructure degradation, and threatened livelihoods. 


The anthropogenic burning of fossil fuels has caused an increase in greenhouse gas emissions such as carbon dioxide, nitrous oxide, and methane, triggering a rise in global temperature. When the temperature of a habitat increases rapidly, organisms are unable to adapt swiftly to these changes. All species have evolved to tolerate a specific range of temperatures which they can survive within, and will become stressed when pushed out of their comfort zone. One consequence that is triggered from a rise in temperature is known as coral bleaching, which occurs in distressed coral reef ecosystems. In a healthy coral reef ecosystem, plankton known as zooxanthellae attach to coral and undergo photosynthesis, which powers the growth of the coral. However, when coral are stressed they can expel the plankton as a survival mechanism, which renders the coral weak and vulnerable-unable to provide a habitat for organisms such as oysters, sea urchins, and numerous fish species.

 

A diagram of coral bleaching. Image source: Australian Government: Great Barrier Reef Marine Park Authority.


The current lack of coral is posing a major threat to countries all over the world, such as in Indonesia and Australia. In Southeast Asia, Indonesia has become the world’s “largest area of threatened coral reefs”. The Great Barrier Reef is another prime example of coral bleaching and its disastrous effects. This reef cover has been subjected to ocean acidification, oil spills, destructive fishing techniques, and pollution, so much so that 60% of these corals “may be lost by 2030.” This jeopardizes the health of thousands of organisms that rely on coral reefs for survival, such as sharks and turtles. This disrupts the food chain and forces the migration of species to new habitats that are unfamiliar and potentially uninhabitable.  


Image source: Phil Walter/Getty Images.


The increase in global temperature of about 1 degree Celsius has additionally triggered a rise in sea level, which can be attributed to two factors: thermal expansion and the melting of ice caps. Thermal expansion is the process by which water molecules absorb heat and thus vibrate faster and expand. A rise in global temperature triggers the acceleration of the melting process, resulting in less ice caps and more water in the ocean. Together, these two processes generate a variety of issues for coastal infrastructure, as well as habitat destruction. 


Plants and corals that once acted as a buffer against high tides and hurricanes are deeper within the ocean, rather than closer towards the surface. Thus, they cannot offer protection against wave shock for coastal infrastructure, resulting in increased susceptibility to damage. Countries such as Haiti, India, Vietnam, China, and Indonesia have felt the wrath of intense storm surges and flooding, disproportionately impacted by rising sea levels. Flooding poses potential risks of contamination of groundwater, loss of land for agricultural or cultural purposes, and increased transmission of disease. Flooding also causes the destruction of homes, displacing the populations living in these vulnerable, flood-prone areas. The United States has already felt the effects of sea level rise, specifically in coastal areas such as Miami, New Orleans, and Boston. New Orleans has been losing around “25 square miles of land per decade to sea level rise”, jeopardizing housing, population health, and habitat loss for Louisiana as a whole. 

     

Additionally, it is vital to acknowledge the substantial amount of carbon being emitted into the atmosphere that is actively decreasing the pH of seawater, altering the chemical makeup of coastal ecosystems and threatening the structural development of marine organisms. When carbon dioxide mixes with water, carbonic acid is formed and ultimately prevents the formation of calcium carbonate. This compound is a building block ingredient for corals and small shelled organisms such as oysters, crabs, and mussels. A lack of calcium carbonate causes these shell-building organisms to struggle to form strong foundational structures, leaving these creatures weak and vulnerable. The increase in carbon absorbed by the ocean also allows for an accumulation of hydrogen ions in the water, lowering its pH. Organisms have strong negative reactions to the increased acidity of water, such as a decline in the ability to detect predators or recognize suitable habitats. 


All organisms forced to endure the consequential effects of these chemical alterations are disadvantaged, as are those that rely on these species for survival. This threatens biodiversity levels as well as food security, especially for countries that rely on seafood for a large portion of their diet. Senegal in West Africa has struggled from this loss of biodiversity, as seafood accounts for 40% of the animal protein intake for the country’s population. Food scarcity has raised the price of seafood, subjecting thousands that cannot afford the price increase to inadequate nutrition. However, those that are able to locate seafood for consumption may ingest microplastics that were accidentally consumed by the organism. This raises potential health concerns, as plastic has the ability to trigger inflammation and oxidative stress in the body. The decreased amount of marine resources available for economic growth may also trigger political tension, as countries may be forced to argue over scarce materials. 


It is necessary to acknowledge the human impacts jeopardizing the health of coastal ecosystems. Human development, specifically on the coast, poses a major threat to these ecosystems as materials from established infrastructure and development projects often run off into the ocean. With the infiltration of hazardous materials, organisms may mistake them for food and die from the consumption of plastic or other foreign objects. The absence of these organisms will trigger a widespread loss of biodiversity, as organisms that relied on species unique to this habitat will suffer. Microplastics have caused immense damage to populations of marine organisms around the world, with its effects most visible in the North Pacific. There, fish ingest around 12,000 to 24,000 tons of plastic annually. The species most at risk of consumption and potential plastic pollution are tuna and grouper, but larger organisms such as sea birds, seals, and sharks are also at risk due to biomagnification


Overfishing has caused a strain on the marine food chain, as the removal of a significant amount of fish leaves less food for predator consumption. Fishing, in general, can be very structurally damaging to habitats. When fishermen trawl for fish, their nets can get caught in coral and marine plants, causing breakage. The wreckage of these plants have devastating impacts on the marine species that occupy the area, as they are left without food or shelter against predators. This has been quite evident in the Hawaiian Islands, as 114,640 pounds of nets accumulate every year along the reef cover. The photo below shows a covered reef on the left, and the subsequent damage to the coral once the net is removed on the right. 


Image source: NOAA Fisheries


Another issue that results from human activity is the use of excess amounts of fertilizer in agricultural practices. This act can be extremely damaging to coastal ecosystems, as this allows worrying quantities of fertilizer to run off into the ocean. This accumulation of fertilizer significantly increases the amount of nutrients in the water, allowing for rapid plant growth. This process is known as eutrophication: extreme plant growth caused by an overload of nutrients in the water. This phenomenon is extremely harmful to coastal ecosystems because it allows for the rampant growth of algae, causing algal blooms or non-penetrable layers of algae to form on the surface of the water. An algal bloom absorbs all of the available oxygen in the water and prevents sunlight from reaching organisms below the layer. Organisms that do not receive enough oxygen suffer hypoxia and can become prone to death. The lack of sunlight and oxygen beneath the layer inhibits plant productivity and decreases biodiversity, allowing for dead zones in the ecosystem. This issue has been extremely relevant in the Gulf of Mexico, and in 2021, this dead zone spanned more than 4 million acres of habitat, having detrimental effects on the marine life inhabiting the area. 


Coastal ecosystems are heavily involved in the regulation of carbon on Earth, as they act as carbon sinks. This means that much of the carbon in the ocean is absorbed by marine plants through the process of photosynthesis. Once absorbed, the carbon is transferred and stored for long-time scales in the biomass and sediments beneath the sea floor. However, the disruption of these habitats caused from climate change and human disturbances has consequential impacts on the carbon cycle. The amount of carbon entering the ocean is too great to be properly regulated and absorbed by its carbon pathways. The destruction of these ecosystems also depletes the amount of plants available to absorb carbon, preventing the regulation of carbon in the ocean. This occurrence is extremely problematic for carbon regulation, as the carbon that was once stored in plants or sediments is released back into the ocean and atmosphere. The disruption of coastal ecosystems essentially removes the carbon storage units in the ocean and also prevents carbon from being absorbed and stored to help combat climate change. 


The protection of coastal ecosystems is necessary to ensure the health of the Earth and its inhabitants. Proper measures must be taken to address the causes of this environmental damage and identify solutions to recuperate and prevent further destruction. The establishment of more marine protected areas, a decrease in coastal development, and the implementation of restrictions on fertilizer quantities for agriculture are just a few courses of action that would lessen the burden on coastal ecosystems. Ensuring the health and safety of these ecosystems will also call on the need for renewable energy, as this would decrease the amount of carbon emitted into the atmosphere that would otherwise be absorbed by the ocean. Major political cooperation is essential in addressing these concerns, as is a public consensus of solutions that could be taken to enact significant change. Implementing these potential solutions will likely aid in the healing of the Earth, allowing for a world that promotes the health of the environment alongside civilization’s future. It is vital to acknowledge the damage being done to coastal ecosystems, the consequences it is having on the climate, and the ways to prevent further environmental degradation.

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