The ‘shifting baseline’ phenomenon: a global perspective

Abstract

In this paper we demonstrate that low level 'artisanal' fishing can dramatically affect populations of slow-growing, late-maturing animals and that even on remote oceanic islands, stocks have been depleted and ecosystems degraded for millennia. Industrialised fisheries have developed during different decades in different regions of the world, and this has almost always been followed by a period of massive stock decline. However, ecosystems were not pristine before the onset of industrial fishing and it is difficult to assess the 'virgin' state of a population given that it may have been subject to moderate or even high levels of fishing mortality for many centuries.A wide range of information is available to help define or deduce historic marine population status. These include 'traditional' written sources but also less conventional sources such as archaeological remains, genetic analyses or simple anecdotal evidence. Detailed information, collected specifically for the purpose of determining fish stock biomass tends to exist only for recent decades, and most fishery assessments around the world (and thus time-series of biomass estimates), are less than 30 years long. Here we advocate using a wider range of multidisciplinary data sources, although we also recognise that it can be difficult to separate natural variability associated with changing climatic conditions from human-induced changes through fishing. We consider whether or not recovery of degraded ecosystems is ever possible and discuss a series of one-way ratchet like processes that can make it extremely difficult to return to a former ecosystem state.

Disruption of historical patterns of isolation by distance in coastal steelhead

“…When natural populations exchange migrants at a rate proportional to their geographic distance, population genetics theory leads to the expectation of a pattern of isolation-by-distance (IBD; Wright 1943), whereby geographic and genetic distance are correlated. However, as has been noted in fisheries and wildlife management (Jackson et al 2001;Newsome et al 2007), human-altered systems often do not provide an accurate representation of historical conditions (shifting baseline syndrome ;Pauly 1995;Pinnegar and Engelhard 2008). From a population genetic perspective, patterns of genetic variation observed in modern populations may not accurately reflect the historical relationships among their ancestral populations.…”

Reservoir Rehabilitations: Seeking the Fountain of Youth

“…See Figure 1 for conceptualization of amplitude, rate, and duration. these responses can lead to a scenario like the shifting baseline syndrome (Pauly 1995;Pinnegar and Engelhard 2008). Specifically, the general public and biologists may have different perspectives on what is a functional ecosystem in the face of processes associated with reservoir aging.…”

Sustainable landscape development and value rigidity: the Pirsig‘s monkey trap

“…While the recovery of the green sea turtle has been wildly successful given the population increase, the green sea turtle is not considered "recovered" because their populations are still below historical levels (Kittenger et al 2013). The recovery to historical levels, however, is not a realistic goal due to the concept of the "shifting baseline syndrome" (Pinnegar and Engelhard 2008;Papworth et al 2009) given that the ecosystem has changed drastically through introduced and invasive species, degradation through human impacts and land runoff, and overexploitation and harvesting. Thus, considering the historical population of sea turtles as a baseline is no longer relevant under the new paradigm.…”