Light Pollution: How Coastal Cities are Impacting Marine Ecosystems

Coastal cities have played a crucial part in societal development throughout human history. Necessary for trade purposes and access to coastal resources, civilizations have been built off of their coastal urban centers. As a result of this historical trend, ocean ecosystems are continuously forced to adapt to human activity. One aspect of anthropogenic activity that has influenced how marine ecosystems function is the artificial light that results from urbanization. Artificial light, while being a more subtle source of pollution compared to littering and chemical runoff, significantly impacts marine wildlife and their ecological functions. 

Light pollution is defined by National Geographic as the “excessive or inappropriate use of artificial light.” Artificially produced light is convenient, as it can be utilized for nighttime transportation, working, and social activities. Light pollution comes from a variety of sources, including but not limited to building lights, ships, offshore rigs, lighthouses, and street lights. In large urban areas, artificial light is especially present as a result of the dense populations that occupy them. In fact, satellite imagery has displayed a significant difference in how bright urban metropolitan areas are compared to rural areas. 

While the light difference is certainly necessary to support the estimated 56% of the global population that live in cities, the constant light has adverse effects on wildlife that live along the coasts of seaside cities such as Boston, Miami, and Los Angeles. A large concern has to do with artificial light influencing sleep patterns of animals which inhabit coastal areas. Many organisms utilize the natural light emanating from the sun and moon as a part of their natural circadian rhythms. However, artificial light waves that penetrate ocean water disrupt these natural patterns, leading to fish becoming more active at night. As a result, hunting patterns and times are altered, changing how species interact with one another. While some species of nocturnal hunters can benefit from these changes, human disruption of natural ecological processes should be limited as much as possible to reduce disruption of biological functions. 

In addition to the feeding habits of marine species, migratory bird patterns can be altered as a result of excessive artificial light, which leads to reduced survival rates. Many species of coastal birds are vulnerable to disorientation due to light pollution, which leads to collisions and delays in migration. Birds may be drawn to the lights while foraging, leading them towards urban environments they are not suited for. For example, according to Jacques Trouvilliez, Executive Secretary of the African-Eurasian Waterbird Agreement, bird species such as “petrels and shearwaters are attracted by artificial lights on land and become prey for rats and cats.” As a result, humans are creating unnecessary deaths and reduced survival rates in coastal and migratory bird species.

Coral reef systems are also impacted by coastal light pollution, which has a cascading effect on a large number of organisms that rely on the reefs. In a 2019 study published in Global Change Biology, researchers found that corals exposed to artificial light were afflicted by chemically reactive forms of oxygen that are detrimental to the coral’s DNA and cellular structure. As a result of those changes, photosynthetic algal symbionts attached to the corals died and declined, slowly killing the coral in the process and further damaging the marine ecosystem’s interworking connections. 

However, there are solutions to the damages caused by coastal light pollution. Urban areas can implement a wide range of different forms of lighting near coastal areas that can significantly reduce the impact of nighttime anthropogenic actions on marine ecosystems. Those solutions include utilizing motion sensors to prevent light sources such as street lamps from staying lit through the night. In addition to motion sensors, transitioning lighting systems near coastal ecosystems to LEDs (light-emitting diodes) is a simpler start. LEDs have a lesser impact on marine life because the light penetrates the ocean less. Even simpler still, turning off all lights in buildings that are not being utilized will not only reduce light pollution, but would also reduce energy use and therefore have further beneficial impacts on the environment. 

Urban settings located along the coast are inevitable in human society. Knowing that societies must take advantage of these coastal settings, the goal should be to reduce impact rather than trying to eliminate it entirely. Government officials and activists can implement a gradual approach to this dilemma, starting with simple and affordable reductions to light pollution. While the negative impacts of urban light pollution are often overlooked, any inimical influences on the environment by humans should be reduced as much as possible. Reducing society’s footprint on the earth’s natural systems, regardless of how obvious, must be a priority for a sustainable future. Without doing so, humans will continue the downward spiral of depleting the ecological wonders left in the world.


Keim, Brandon. “Light Pollution Could Cause Problems for Coral Reefs.” Anthropocene, 16 Oct. 2019, pacts%20were%20significant.,inside%20the%20corals%20fluctuated%20abnormally. 

“Light Pollution Solutions.” International Dark-Sky Association, 10 Oct. 2018, tion%20sensors%20and%20timers,and%20save%20even%20more%20energy.&text =Switching%20to%20LED%20lighting%20allows,empty%20office%20buildings%20at %20night. 

“Light Pollution.” National Geographic, National Geographic, 

O’Connell-Domenech, Alejandra. “A New Study Maps out Coastal Areas Impacted by Light Pollution.” The Hill, The Hill, 15 Dec. 2021, l-areas-impacted-by-light/. 

Portala, Juliette. “The Dark Side of Light: Coastal Urban Lighting Threatens Marine Life, Study Shows.” Mongabay Environmental News, 27 Jan. 2023, ine-life-study-shows/#:~:text=But%20when%20artificial%20lights%20interfere,the%20 water%20is%20lit%20up. 

Roberts, Mark. “Bright Lights, Big Cities.” World Bank Blogs, World Bank, 7 Nov. 2013, 

“Urban Development.” World Bank, World Bank, 

Wheeling, Kate. “Artificial Light May Alter Underwater Ecosystems.” Science, 28 Apr. 2015, 

“World Migratory Bird Day Illuminates the Dark Side of Light Pollution | UN News.” United Nations News, United Nations, 13 May 2022, %20patterns,resulting%20in%20disorientation%20and%20collisions.