Effects of global warming on marine mammals

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The effects of global warming on marine mammals are of growing concern. Many of the effects of climate change are currently unknown due to its unpredictability, but there are many effects that are becoming increasingly apparent today. In fact, it is not certain that the current trend of global warming is a long-term trend.[1] Some effects are very direct such as loss of habitat, temperature stress, and exposure to severe weather. Other effects are more indirect such as changes in host pathogen associations, changes in body condition because of predator–prey interaction, changed in exposure to toxins, and increased human interactions. These are just a few examples of what marine mammals are dealing with as a result of rapid climate change.[2] There are a number of marine mammals that have been affected by climate change including walruses, seals, penguins, and polar bears.[3]


Marine mammals have evolved to live in the ocean, but the effects of climate change are rapidly altering their habitat.[4][5][6][7] The climate change for arctic marine mammals by studying the difference in their habitat, distribution, abundance, movement and migration, body conditions, behavior, and their sensitivity. The climate change is drastically changing, so it is hard for some arctic marine mammals to adapt to the new conditions as quickly as needed, so the arctic marine mammals are being studied to see what happens to them due to the high stress they are put in due to the rapidly changing climate change. These climate changes put the arctic marine mammals in immense pressure and stress, due to this many species who cannot adapt begin to slowly die off due to the extra stress.[8] As levels of greenhouse gases in the atmosphere increase they trap heat which causes an overall warming of the planet. During the last century, the global average land and sea surface temperature has increased dramatically.[9] Warming has reached down to about 700 meters[10] and more (per a study which finds that 30% of the ocean warming, over the past decade, has occurred in the deeper oceans below 700 meters).[11][12] Many marine mammal species require specific temperature ranges in which they must live. The warming of the ocean will cause changes in the species migration or area that they inhibit. The species that cannot relocate due to some type of barrier will be forced to adapt to the increasingly warming sea waters or they will face extinction. Many of the species ranges are being pushed further and further north as water temperatures increase and they will soon have nowhere else to go.

The rise in sea level affect the coastal habitat and the species that rely on it to survive.[13] T he rising sea levels are causing erosion of the beaches, so this then causes the turtles to have a hard time finding a spot to lay their eggs. The rising temperature are also causing problems for the turtles because the temperature of the sand determines the sex of the eggs, so many places are having a 90% production of females and if the temperature rises by just one degree, there could potentially be no more male turtles. The right whales have been on the endangered species list since the 1970s and the population keep declining because of the decline of zooplankton. Because of the climate change, the population of zooplankton is decreasing and since this is the right whale's main food source, the female whales are not able to bulk up for the calving process. Moreover, changes in sea ice also affect the reproductive process of penguins. Many surveys had proved the relationship between reduction of ice and the decrease of penguin population. One of those states that decreases in sea ice makes the colony of emperor penguins shrink because they need ice for their breeding process. Other species of penguin, such as Adelie, chinstrap, and gentoo are also influenced by decreasing sea ice.[14] The seals are affected by the climate change because of the rapid increase of the melting ice. The seals use the ice to rest between their searches for food. With the increase of melting ice, the seals could be in trouble.[15] This habitat is often used by pinnipeds as haul-out sites. In order to combat rising sea levels in areas inhabited by humans, the construction of sea walls has been proposed; however, these walls may interfere with the migration routes of several marine mammal species. These routes can be very important to some marine mammal species for reaching feeding and breeding grounds.

Increasing temperature does have impact on the population of marine mammals. Indeed, Warmer temperature will lead to more snowfall and rainfall. In one study, it is indicated that warm temperature and increased snowfall can lead to decreasing of Adelie penguins population, and the population will decrease more in a place that has a lot of snow. Moreover, warm temperature negatively influence the breeding process of adult penguins, and that makes the number of chicks decrease.[16]

Changes in the temperature ranges will also change the location of areas with high primary productivity. These areas are important to marine mammals because primary producers, such as plankton, are the food source of marine mammal prey or the marine mammals prey themselves. Marine mammal distribution and abundance will be determined by the distribution and abundance of its prey. Migration of marine mammals may also be affected by the changes in primary productivity. Water temperature changes also affect the turbulence of the ocean which has a major impact on where plankton and other primary producers are dispersed.[17]

Increased glacier ice melt also impacts ocean circulation because, due to the increase of freshwater in the ocean, salinity concentrations in the ocean are changing. Thermohaline circulation may be altered by increasing amounts of freshwater in the ocean. Thermohaline circulation is responsible for bringing up cold, nutrient-rich water from the depths of the ocean, a process known as upwelling. This may affect regional temperatures and primary productivity.

Susceptibility to disease is also thought to increase while reproductive success may decrease with increasing ocean temperatures.

The world's oceans absorb a large amount of carbon dioxide from the atmosphere, which causes an increase in carbon dioxide concentrations and decreases its overall pH, increasing ocean acidification.

Polar bears[edit]

Polar bears are one of the marine mammals that are at risk due to climate change. The biggest issue for polar bears related to climate change is the melting of ice as a result of increasing temperatures. When the ice melts, the bears lose habitat and they lose food sources. Although polar bears have been known to eat more than 80 species of animals, most of their diet consists of seals.[18] As the ice melts, polar bears lose their habitat and so do their prey. Though polar bears have many options as far as what they can eat, their main sources of food depend on the same ice that they do. This causes numerous issues for the bears. One problem is that they have to travel farther to find food. Sometimes, this leads them to places that are populated by humans which causes problems for the bears and the humans. Having to travel also makes it more difficult for polar bears to find mates, and there have been an increasing number of polar bear drownings due to becoming exhausted by having to swim farther to find ice.[19] As a result of global warming, the number of polar bears is declining.


Penguins are very easily affected by climate warming, and they are in the International Union for Conservation of Nature's Red List. Every change caused by global warming negatively influences penguins’ distribution and population. One of those changes is the decline of penguin’s prey and the cover of ice. Most penguins need ice to breed and raise chicks. Adelie penguins and emperor penguins are two species that depend on ice the most. Therefore, the shrink of ice due to climate change significantly affects the reproductive process of both the adelie and emperor penguins. Moreover, climate warming brings more snowfall, which could influence the survival of both chicks and adult penguins. Researches also show that there are decreasing in population of another species of penguins due to climate changes. Indeed, African penguins had decreased sharply.[20]


  1. ^ Castilla, Juan Carlos. "Marine Ecosystems, Human Impacts on". Encyclopedia of Biodiversity (2 ed.). Academic Press. pp. 56–63. 
  2. ^ Burek, Kathy. "Effects of Climate Change on Arctic Marine Mammal Health". Ecological Society of America. JSTOR 40062160. 
  3. ^ "Pollution, habitat loss, fishing, and climate change as critical threats to penguins". Conservation biology. 
  4. ^ Hardwood, 2001
  5. ^ Simmonds and Isaac, 2007
  6. ^ Tynan and DeMaster, 1997
  7. ^ Learmonth et al, 2006
  8. ^ Laidre, Kristin L.; Stirling, Ian; Lowry, Lloyd F.; Wiig, Øystein; Heide-Jørgensen, Mads Peter; Ferguson, Steven H. (January 1, 2008). "Quantifying the Sensitivity of Arctic Marine Mammals to Climate-Induced Habitat Change". Ecological Applications. 18 (2): S97–S125. JSTOR 40062159. 
  9. ^ Map Shows Vast Regions of Ocean Are Warmer March 30, 2013 Scientific American
  10. ^ Warming Ocean Threatens Sea Life; Warming down to 700 meters could also affect currents, weather March 30, 2013 Scientific American
  11. ^ New Research Confirms Global Warming Has Accelerated March 25, 2013 Skeptical Science
  12. ^ "Distinctive climate signals in reanalysis of global ocean heat content". Geophysical Research Letters. 40: 1754–1759. doi:10.1002/grl.50382. 
  13. ^ Glick, Patrick; Clough, Jonathan; Nunley, Brad. "Sea-Level Rise and Coastal Habitats in the Chesapeake Bay Region" (PDF). National Wildlife Federation. Retrieved November 8, 2014. 
  14. ^ Boersma. "Penguins as marine sentinels". 
  15. ^ "Endangered Species and Habitats". Climate Change: The Effects on Ocean Animals. [permanent dead link]
  16. ^ "Pollution, habitat loss, fishing, and climate change as critical threats to penguins". 
  17. ^ Castilla, Juan Carlos. "Marine Ecosystems, Human Impacts on". Encyclopedia of Biodiversity (2 ed.). Academic Press. pp. 56–63. 
  18. ^ Derocher, Andrew. Polar Bears: A Complete Guide to Their Biology and Behavior. Johns Hopkins University Press. p. 84. 
  19. ^ Parsons, Edward; Milmoe, B.J.; Rose, Naomi. "Polar Bears". Encyclopedia of Global Warming & Climate Change (2 ed.). SAGE Reference. p. 1114. 
  20. ^ Encyclopedia of Global Warming & Climate Change. SAGE. 


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