Effects of global warming on marine mammals

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The effect of global warming on marine mammals is a growing concern. Many of the effects of global warming are currently unknown due to unpredictability, but many are becoming increasingly evident today. 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.[1] Marine mammals that have been affected by climate change include walruses, seals, and polar bears.[2]


Marine mammals have evolved to live in oceans, but climate change is affecting their natural habitat.[3][4][5][6] Some species may not adapt fast enough, which might lead to their extinction.[7]

During the last century, the global average land and sea surface temperature has increased due to an increased greenhouse effect from human activities.[8] Warming has even reached depths of more than 700 meters[9] (30% of ocean warming over the past decade has occurred in the deeper oceans below 700 meters).[10][11] Many marine mammal species require specific temperature ranges to survive. Ocean warming will therefore lead to increased species migration, as endangered species look for a more suitable habitat. If a species cannot successfully migrate to a suitable environment, unless it learns to adapt to rising ocean temperatures, it will face extinction. Sea level rise is also important when assessing the impacts of global warming on marine mammals, since it affects coastal environments that marine mammals species rely.[12]

Primary productivity[edit]

Changes in temperatures change the location of areas with high primary productivity. Primary producers, such as plankton,[13][14][15][16] are the main food source for marine mammals such as some whales. Species migration will therefore be directly affected by locations of high primary productivity. Water temperature changes also affect ocean turbulence, which has a major impact on the dispersion of plankton and other primary producers.[17] Due to global warming and increased glacier melt, Thermohaline circulation patterns may be altered by increasing amounts of freshwater released into oceans and, therefore, changing ocean salinity. Thermohaline circulation is responsible for bringing up cold, nutrient-rich water from the depths of the ocean, a process known as upwelling.[citation needed]

Polar bears are one of the marine mammals that are most 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, polar bears lose their habitat and food sources. Although polar bears have been known to eat more than 80 species of animals, most of their diet consists of seals, which are also endangered by global warming.[18] There have been an increasing number of polar bear drownings because they become exhausted by having to swim farther to find ice or prey.[19]


  1. ^ Burek, Kathy A.; Gulland, Frances M. D.; O'Hara, Todd M. (2008). "Effects of Climate Change on Arctic Marine Mammal Health" (PDF). Ecological Applications. 18 (2): S126–S134. doi:10.1890/06-0553.1. ISSN 1051-0761. JSTOR 40062160.
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  5. ^ Tynan, Cynthia T.; DeMaster, Douglas P. (1997). "Observations and Predictions of Arctic Climatic Change: Potential Effects on Marine Mammals" (PDF). Arctic. 50 (4): 308–322. doi:10.14430/arctic1113.
  6. ^ Learmonth, JA; Macleod, CD; Santos, MB; Pierce, GJ; Crick, HQP; Robinson, RA (2006). "Potential effects of climate change on marine mammals". In Gibson, RN; Atkinson, RJA; Gordon, JDM (eds.). Oceanography and marine biology an annual review. Volume 44. Boca Raton: Taylor & Francis. pp. 431–464. ISBN 9781420006391.
  7. ^ 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. doi:10.1890/06-0546.1. JSTOR 40062159.
  8. ^ Map Shows Vast Regions of Ocean Are Warmer March 30, 2013 Scientific American
  9. ^ Warming Ocean Threatens Sea Life; Warming down to 700 meters could also affect currents, weather March 30, 2013 Scientific American
  10. ^ New Research Confirms Global Warming Has Accelerated March 25, 2013 Skeptical Science
  11. ^ Balmaseda, Magdalena A. (2013). "Distinctive climate signals in reanalysis of global ocean heat content". Geophysical Research Letters. 40 (9): 1754–1759. doi:10.1002/grl.50382.
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  14. ^ Vázquez-Domínguez, E.; Vaqué, D.; Gasol, JM. (2007). "Ocean warming enhances respiration and carbon demand of coastal microbial plankton". Global Change Biology. 13 (7): 1327–1334. doi:10.1111/j.1365-2486.2007.01377.x. hdl:10261/15731.
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  16. ^ Mazuecos, E.; Arístegui, J.; Vázquez-Domínguez, E.; Ortega-Retuerta, E.; Gasol, JM.; Reche, I. (2012). "Temperature control of microbial respiration and growth efficiency in the mesopelagic zone of the South Atlantic and Indian Oceans". Deep Sea Research Part I: Oceanographic Research Papers. 95 (2): 131–138. doi:10.3354/ame01583.
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  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.


  • Poloczanska, E. S., Babcock, R. C., Butler, A., Hobday, A. J., Hoegh-Guldberg, O., Kunz, T. J., Matear, R., Milton, D. A., Okey, T. A., & Richardson, A. J. 2007. "Climate change and Australian marine life". Oceanography and Marine Biology: An Annual Review, 45, 407–478.
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