Marine Climate Change Impacts

Impacts on Wildlife

Plankton

Fisheries

Marine Mammals

Sea Birds

IPCC
Climate Change 2007: Impacts Adaptation and Vulnerability

Climate Impacts on Marine Mammals

Marine mammals are sensitive indicators of changes in ocean environments. One of the impacts of a changing climate on the marine mammals that feed from the top of the food chain is associated with changes in prey abundance due to physical changes such as increased sea temperature. For example, in the North Pacific and western Arctic, synchronised and extreme fluctuations of abundance of mammal populations have been related to the response to physical changes, including climate warming. The climate changes, beginning in the 1990s and associated with El Niño conditions in combination with overfishing, have been linked to behavioural changes in killer whales. These changes drastically reduced sea otter abundance along the Aleutian Islands, which in turn changed the ecology of the kelp forests.

Climate change also may have an effect on access to prey among marine mammals. For instance, extended ice-free seasons in the Arctic could prolong the fasting of polar bears, with possible implications for the seal population. Reduced ice cover and access to seals would limit hunting success by polar bears and foxes, with resulting reductions in bear and fox populations.

Because global climate change is likely to have profound impacts on sea-ice extent and duration, it is in this habitat where the initial impacts on marine mammals may be first evident. Reductions in sea ice have been predicted to alter the seasonal distributions, geographic ranges, migration patterns, nutritional status, reproductive success, and ultimately the abundance of Arctic marine mammals. Studies recognising multi-year to decadal variability in marine biotic systems include zooplankton over 5 decades in the eastern Pacific (with connections to El Niño), and on soft bottom macrobenthic communities in the northeast Atlantic (with connections to the North Atlantic Oscillation).

It is difficult to obtain reliable estimates of cetacean population sizes. The UK has taken part in a coordinated, multi-national survey of cetaceans in the North Sea and associated waters in 1994 and in European Atlantic waters in 2005 (SCANS - Small Cetacean Abundance in the North Sea and SCANS II - as SCANS but also including European Atlantic waters). One of the aims of SCANS II is to develop statistically robust methods to ascertain cetacean density at appropriate geographical scales. This will be important for monitoring cetacean populations and the possible effects of climate change on those populations in the future.

Additional information and key links

Breaking waves
Climate variability and north Atlantic right whales. (pdf)

Arctic Climate Impact Assessment report, Chapter 9

Arctic Climate Impact Assessment Report
Ch. 9 Marine Systems

Key references

ACIA, 2005. Arctic Climate Impact Assessment. Cambridge University Press. 1042pp.

Defra. 2005. Charting Progress: An Integrated Assessment of the State of UK Seas. Report 3: Marine Habitats and Species © Crown copyright 2005

Greene, C.H., A J. Pershing, R.D. Kenney and Jossi, J.W. 2003. Impact of Climate Variability on the Recovery of Endangered North Atlantic Right Whales. Oceanography, 16 (4).

IPCC, 2001: Climate Change 2001: Impacts, Adaptation, and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. [McCarthy, J.J., O.F. Canziani, N.A. Leary, D.J. Dokken, K.S. White. (eds.)] Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1032pp.

Sea Mammal Research Unit (SMRU). 2005. Scientific Report 1999-2004. 39pp.