Marine historical ecology: Informing the future by learning from the past

Background/Question/Methods: Marine historical ecology developed more recently than terrestrial historical ecology and faces unique challenges, namely that the period of direct observation in the ocean is substantially shorter than that on land. With rapid changes observed—including the cascading effects of the loss of large predators and large-scale declines in foundational species—there is a distinct need to understand the basal drivers of change, as well as the restoration potential of marine and coastal ecosystems. Here, I give two examples of marine historical ecology research, which demonstrate the essential missing information that historical data can provide on ecosystem change and restoration potential in the ocean. First, I quantify change in the size and species composition of the largest predatory reef fish over five decades using a time series of historical photographs of trophy fish caught on recreational fishing boats in Key West, Florida. Second, I use high-resolution historical nautical charts from the period of British exploration to quantify changes to coral extent over 240 years in the Florida Keys.

Results/Conclusions: Analysis of historical trophy fish photographs identified a 90% decline in the size of large reef fish, with a loss of the largest species over time. Likewise, analysis of historical nautical charts identified a 52% decline in coral across the Florida Keys. Importantly, it identified a strong spatial dimension to this decline; coral in Florida Bay and near shore declined by 88% and 69% respectively, while offshore coral remained largely intact. These results have important implications for understanding ecosystem change and recovery potential, and underscore a need to expand the use of non-traditional data types in historical ecology research to more accurately quantify human-driven ecosystem change. For example, the near complete elimination of near-shore coral represents an underappreciated spatial component of the shifting baseline syndrome, with important lessons for other species and ecosystems. In particular, assessments of change focusing only on species’ extant range may overlook larger-scale loss over longer timeframes and provide overly optimistic views of their current conservation status and underestimate restoration potential.