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This book offers an interdisciplinary view of the biophysical issues related to climate change. Climate change is a phenomenon by which the long-term averages of weather events (i.e. temperature, precipitation, wind speed, etc.) that define the climate of a region are not constant but change over time. There have been a series of past periods of climatic change, registered in historical or paleoecological records. | Part 2 Changes in Fauna and Flora 11 Review of Long Term Macro-Fauna Movement by Multi-Decadal Warming Trends in the Northeastern Pacific Christian Salvadeo1 Daniel Lluch-Belda1 Salvador Lluch-Cota2 and Milena Mercuri1 1Centro Interdisciplinario de Ciencias Marinas del Institute Politécnico Nacional 2Centro de Investigaciones Biológicas del Noroeste La Paz B.C.S. Mexico 1. Introduction Worldwide marine ecosystems are continuously responding to changes in the physical environment at diverse spatial and temporal scales. In addition to the seasonal cycle other natural patterns occur at the interannual scale such as El Nino-La Nina Southern Oscillation ENSO with a period of about three to five years Wang Fiedler 2006 . When ocean conditions stay above or below the long-term average for periods of 10 to 20 years we recognize decadal fluctuations Mantua et al. 1997 and those with periods longer than 50 years are known as regime Lluch-Belda et al. 1989 . On the ocean marine populations respond to these variations in different ways such as changes in their distribution and abundance. Evidence suggests that this multi-decadal scale climate variations are cyclic which generates recurrent changes in the production level of marine ecosystems in ways that may favor one species or a group over another. Abrupt changes between multi-decadal phases are known as regime shifts Overland et al. 2008 . The best documented regime shift in the North Pacific occurred in the mid-1970 with strong physical and biological signals including ocean productivity Ebbesmeyer et al. 1991 Roemmich McGowan 1995 strong biomass and distribution changes in sardine and anchovy populations Kawasaki 1983 Lluch-Belda et al. 1989 and several other fish populations Beamish et al. 1993 Mantua et al. 1997 Holbrook et al. 1997 . These changes impacted marine food webs and ultimately affected the distribution and survival of marine top predators such as seabirds and marine mammals Trites Larkin 1996 Veit et al. .
