The term “shifting baselines” refers to the way in which significant changes to an ecosystem are measured against previous baseline states, which themselves are significantly different from the original state of the system. Daniel Pauly (1995) popularized the term, which refers to fisheries management where scientists sometimes fail to identify the correct “baseline” population size (i.e., how abundant a fish species population was before human exploitation), and thus use a shifted baseline when evaluating unfished population size. A species that was abundant hundreds of years ago may have experienced declines over that whole period, but the population status in recent past decades is incorrectly considered as the appropriate reference point for current population management. In this way, large declines in species over long periods of time can be masked, with each human generation ignorant of previous conditions.

Hobday, A.J. 2012. Review of Shifting Baselines: The Past and the Future of Ocean Fisheries, edited by J.B.C. Jackson, K. Alexander, and E. Sala. Oceanography 25(1):306–308, https://doi.org/10.5670/oceanog.2012.35.

Pauly, D. 1995. Anecdotes and the shifting baseline syndrome of fisheries. Trends in Ecology and Evolution 10(10):430.
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