Implications of Global Change to Local Archaeology

By Lindsey Cochran, Ph.D.

University of Georgia, Laboratory of Archaeology

Emotionally disheartening article ahead. Beware.

Scientists continue to improve models that predict both the mechanism and result of climate changes, and sadly each prediction is more dire than the last. Modeling predictions that used to assume a 1m global sea level rise (GMSLR) now anticipate at least double that by 2100. We now understand that while greenhouse gas emissions are accelerating slightly above exponential rates and thus appearing to be following a logarithmic rather than linear scale, the IPCC anticipates a speeding up of the effects of these emissions. Because of this suite of accelerating climate effects, built in environmental protections to archaeological sites, such as the mangrove swamps in Florida, the oyster beds around the mouth of the Mississippi, or migrations of the marshy estuaries and back-barrier islands on the Georgia and Carolina coasts are shifting more abruptly decades before impacts of this degree were initially predicted.

If you need a refresher on the impacts of climate change beyond a warming earth and rising sea levels, this 2018 New York Times article provides an excellent summary of the dramatic difference between 1.5℃ and 2℃. For a slightly more involved explanation, check out this NASA briefing. And finally for the tech-heavy nerds we all know and love, CMIP and IPCC provide excellent explanations and links to recent scientific literature. 

Archaeologists need to prepare for cascading effects from climate change when creating strategies to mitigate site destruction or simply a timeline to document resources as they succumb to those effects. Rather than presenting a singular case study here, I’d like to illustrate some of these cascading effects by describing a selection of impacts from melting Arctic sea-ice to the archaeology of the southeast United States. To truly prepare for climate changes it’s critical to understand the big picture so that we can adapt our local responses to fast- and slow-moving regional and global events. As large scale computational modeling improves, such as with the CMIP simulations, specific inter-disciplinary interpretations likewise change and improve.

An article of note from March 2020 uses the CMIP6 simulation to estimate that Arctic Ocean will be sea-ice free in September for the first time come 2050 (Notz et al. 2020).  September Arctic sea-ice is one of NASA’s “Vital Signs of the Planet,” and the area of the ice extent is now declining at a rate of 12.85% per decade relative to 1981 to 2010 averages. The implication of these studies is that the world is changing more swiftly and more violently than previously imagined. Why should archaeologists care about climate change on the global scale, and for that matter Arctic sea-ice?

Arctic sea-ice is important to consider when studying archaeology of plantation archaeology on Georgia’s barrier islands, for example, because of the suite of cascading effects that stem from a progressively smaller volume of global ice. Generally speaking, the rapid disappearance of Arctic sea-ice impacts the following, many of which are positive feedback loops: (1) albedo effect; (2) thawing permafrost; (3) melting ice-sheets; (4) trapped outgoing longwave radiation; (5) warming inland waterways like rivers, streams, and lakes; and (6) shifting oxygen and nitrogen ratios. Each of these types of changes have significant global effects that impact regions and localities in various and largely unsynthesized ways, as the science is always changing and improving on itself, making immediate estimates of the impact of specific climate changes to a particular site-specific place quite challenging. The table below summarizes effects of sea-ice, broad implications of those effects, gives a sample of changes that will most directly impact archaeological resources, and provide an archaeological scenario or site specific example of impacts, most of which are drawn from the southeast United States. 

Climate change simulations constantly grow in complexity and accuracy, and sadly the current trends indicated in those simulations are become more dire. As archaeologists, it is important to understand, at least superficially, the big [read: overwhelming] picture of climate change because, simply put, our local responses to the archaeology of climate change need to take into consideration broader syntheses of change. These changes are due to a complex multiplicity of causes that each impact archaeological resources in multi-dynamic ways. Implications from any of the six impacts from melting Arctic sea-ice could easily be applied to any coastal site on the Eastern seaboard.

Now, archaeologists that deal with climate change are asked not only to interpret the past within a historical context but also to situate those resources within a cloudy, submerged future. Archaeologists are well poised to join this broader conversation because we can provide a contextual depth to paleoenvironmental, historical, and near-historical data to interpret an environmental baseline for local and regional changes. By the nature of our research, we are multi-disciplinarian scientists. The flexibility of our mental gymnastics are all the more important when evaluating and interpreting research from the climate sciences and how their results impact analysis of cultural resources.