2.2.2 Shifting baselines

Human activity has caused significant environmental change for millennia 44,45 and this process has accelerated with a growing human population and burgeoning resource use over the past two centuries.46,47,48 The long history of impacts can make it difficult to identify suitable baselines, or starting points, from which to assess environmental change.49 Shifting environmental baselines can occur when, as generations pass, there is a perception that the current or recent past condition of habitats or species represents a natural state despite progressive degradation.50 This is especially the case where historical or anecdotal information is not effectively considered.50 In this way, progressive degradation, such as large declines in species diversity over long periods of time 50,51 or the current pace of global warming,52 may not be accurately recognised. Shifting baselines can present challenges for sustainably managing commercial species 53 and for restoring degraded ecosystems.54 

For all these reasons, it is important to acknowledge the risk of using a shifted baseline to underpin a current assessment. Determining the condition of ecosystems or populations of species back through time is often complicated by the patchiness of records or reliance on anecdotal evidence. Without systematic monitoring and careful consideration of natural drivers, it can be challenging to determine whether local declines represent longer-term trends or regional-scale change.55 

Perceptions of ecosystem condition can be skewed by shifting baselines

In many parts of the world, coral reefs have experienced significant depauperation compared to their historical condition, including declines in coral diversity and cover.56,57 Although wide-scale systematic monitoring of - shallow-water coral reefs in the Reef has only been conducted since 1983,58 longer-term declines in indicators such as coral cover have been demonstrated at some locations through multiple lines of evidence, including coral and sediment cores.59 Combining scientific and traditional knowledge helps to promote a more holistic understanding of environmental changes, and has been demonstrated to improve environmental assessment and management.60 Careful analysis of evidence from archival sources and scientific records (as well as anecdotal information) can provide important insights into the past and help avoid shifting baseline syndrome. The case of giant grouper illustrates this point.51

Reaching up to 400 kilograms and more than 2.5 metres in length,61 the giant grouper is the largest bony fish occurring in the Region. Typically solitary, the species occurs naturally at low abundance across its range.62 Although protected in Australia since 1994, the species was once highly prized in recreational fisheries and continues to be fished across other parts of its distribution.63 Despite anecdotal and short-term evidence of severe localised depletions, relatively little is known of the species’ life history or historical abundance. The global population trend for this species is downwards, noting data deficiencies.62 More locally, shifting baselines may be helping to mask population trends in giant grouper, given the lack of data and limited intergenerational memory on past abundances (aside from that held by Traditional Owners).

In an attempt to shed light on historical baselines, recent research reconstructed giant grouper population trends in Queensland from fishing records reported in newspaper archives.51 The study reveals a significant decline in the relative abundance of giant grouper between 1860 and 1958. This is based on a decrease in probability (dropping from 81 per cent to 2 per cent) of catching giant grouper in a popular recreational fishery over that period.51 This study highlights the importance of archival sources in uncovering historical population trends and assisting in detecting shifting baselines.

The assessments below consider available evidence for each habitat and species component, including recent information and historical trends where available.

References
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