Anthropogenic impact throughout theworld has caused numerous and irrevocable changes in ecosystems. This impact isseemingly as exponential as our own population growth has been since the 1960s–from 3 billion in 1960, to 7.4 billion in 2016 (worldbank).
Despite thesechanges being obvious when looking at landscape change and at historical ecologicaldata, many find it difficult to recognize these changes in the long term. Especiallyin marine environments, which is not a habitat we directly interact in and cansee the changes happening in. This failure to recognize changes, and assumingthe present levels of biodiversity and environmental context is what has alwaysbeen is called the “shifting baselines syndrome,” a term coined by Daniel Paulyin 1995.
Shifting baseline syndrome is a dangerous perceptual trap that may leadto constant downgrading of environmental reference conditions in restoration orconservation management plans. In a paper by Papworth et al(2008), it is proposed that this baseline shifts due to two different modes of “amnesia.”The first, generational amnesia, occurs because younger generations are notaware of past biological conditions, this can be attributed to age or justexperience. The second, personal amnesia, is where individuals forget their ownexperience.
In the first case, as there is a loss of older generations overtime, there is a loss of that information of normality. Perhaps as there is agenerational shift in the workforce, the standards of conservation are lowerdue to the fact they are unaware of previous levels of biodiversity. In thesecond, it can be attributed to mere forgetfulness, or perhaps by theover-focus on only recent ecological data. A case study of a rural village inYorkshire, England interestingly illustrated both personal and generationalamnesia in a case of a shifting baseline of most common bird species in thearea (Papworth et al, 2008).
Fifty people were asked to identify the three mostcommon bird species now and twenty years ago. This perceived data was able tobe compared to actual trends due to a great availability of historical data of birdpopulations in the area. The study found that 36% ofrespondents had a static view of the abundance of species change (they namedthe same three species for both periods of time). While age or interest inbirds did not seem to have a significant effect on this fact, individuals weremore likely to name species that are more abundant now than those more abundantin the past– an example of personal amnesia. Older respondents were able to moreaccurately name the three most common bird species in the past, and alsothought more species had changed than younger respondents (Figure 1). Devastating cases of shiftingbaselines can be seen throughout the fishing industry.
Usually illustrated bynumbers and graphs, changes in average fish weights and species abundance arealready startling– but a paper by McClenachan (2012) gives this shift in a muchmore personal touch. By looking at sport fishing “largest catch” photos fromthe 1950s to the 2000s, it is apparent there is very big change in the size andvariety of fishes caught in the Florida Keys (Figure 2). This change happenedduring a time when there was a “right to fish” movement by local anglers, toprotect their fishing rights. However, this increase in sports fishing withincreasing commercial fishing pressures exhausted an already strained reefecosystem. Because the size of the trophy boards was verifiable, the author wasable to use the photographs to measure the fish. It was found both the averagesize decreased (Figure 3) and the species composition significantly changedover time (Figure 4). Figure 2: Photographs of fishcaught on recreational charter boats in Florida Keys from 1958, 1985, and 2007(McClenachan, 2012). Figure 3: Mean size of (a) trophy fish (b)trophy fish excluding protected species, and (c) sharks (total length) in1956–1960, 1965–1979, 1980–1985, and 2007 (McClenachan, 2012).
Figure 4: Species composition of trophyfish from largest to smallest. The mean size of each group within time periodis indicated with shading (McClenachan, 2012).These examples are but two of manycases of species abundance, frequency, or size change where the baseline ofwhat is normal changes over time. This has very serious implications forconservation – if the bar is continuously lowered (or made inaccurate) for whatis ideal or normal, conservation efforts can be seriously weakened from the start.Considering how difficult it already is to get the finances and policies inplace to make conservation happen, this is a serious matter. Shifting baselinesnumb us to the reality of how much has changed in our environment and howserious the problems are. To remedy this, historical data should be studied tocreate more accurate perspectives. Another strategy is to record and encouragethe sharing of local knowledge– older generations can share their knowledge withscientists and younger generations to help keep in mind how things arechanging.
Implementing or expanding citizen science projects of seasonal or annualmonitoring of species to create a reliable record of species distributionscreates a more reliable historical record.