Effects of climate change on marine mammals

Climate change is a cause of increasing concern to scientists and it will have dramatic effects on marine mammals. The increase of carbon dioxide and other greenhouse gases into the atmosphere are thought to be the main cause of climate change or global warming. Exactly how climate change will affect the ocean, which is home to marine mammals, is hard to predict since there are so many factors that affect ocean ecosystems. How all these, such as weather events and salinity, will interact is highly unpredictable. Using global climate models (GCM)s scientists can get a general idea of how climate change will impact the ocean environment in the future.

Marine mammals have evolved to live in the ocean, but the effects of climate change may be altering their habitat more rapidly than they can adapt to the changes.

As levels of greenhouse gases in the atmosphere increase, they trap heat which causes an overall warming of the planet. During the last century, global average land and sea surface temperature has increased dramatically. Many marine mammal species require specific temperature ranges in which they must live. The warming of the ocean will cause changes in species range. Those species that cannot relocate due to some barrier will be forced to adapt to the increasingly warming sea waters or else risk going extinct. Many species ranges are being pushed further and further north as water temperatures increase and will soon have nowhere else to go.

Not surprisingly, glacier ice melt has increased while sea ice extent and thickness has decreased as temperatures keep rising. Rises in sea level affect coastal habitat and the species that rely on it. This habitat is often used as haul out sites for several pinniped species. 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 for reaching feeding and breeding grounds.

Changes in temperature ranges will also change the location of areas with high primary productivity. These areas are important to marine mammals because primary producers are the food source of marine mammal prey or are the marine mammal 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.

Increased glacier ice melt also impacts ocean circulation 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 worlds oceans absorb a large amount of carbon dioxide from the atmosphere and causes an increase in carbon dioxide concentrations and a decrease its overall pH, increasing ocean acidification.

References

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.

Hardwood, J.. 2001. Marine mammals and their environment in the twenty-first century. Journal of Mammology, 82(3), 630-640.

Learmonth, J.A., Macleod, C.D., Santos, M.B., Pierce, J.G., Crick, H.Q.P. & Robinson, R.A. .2006. Potential effects of climate change on marine mammals. Oceanography and Marine Biology: An Annual Review, 2006, 44, 431-464.

MCCIP. 2006. Marine Climate Change Impacts Annual Report Card 2006. (Eds. Buckley, P.J., Dye, S.R., & Baxter, J.M..), Summary Report, MCCIP, Lowestoft, 8pp.

Simmonds, M.P. & Isaac, S.J. .2007. The impacts of climate change on marine mammals: Early Signs of Significant Problems. Oryx, 41(1), 19-26.

Tynan, C.T. & DeMaster, D.P.. 1997. Observations and predictions of Arctic climate change: potential effects on marine mammals. Arctic, 50(4), 308-422.

External links

• Marine Mammal Commission
• United Nations Environment Programme World Conservation Monitoring Centre
• Intergovernmental Panel on Climate Change