Burial, erosion, and transformation of archaeological landscapes: Case studies from southern New Zealand (Aotearoa)

A high proportion of archaeological sites are located on the world's shorelines and recent research has documented the vulnerability of these sites to coastal processes and climate change. However, archaeological landscapes on many temperate coasts have already been degraded as a result of changes in dune dynamics related to changes in dune vegetation. These changes have produced marked spatial and temporal variations in patterns of burial and erosion in transgressive dune systems. This paper examines the modification and conservation of archaeological landscapes from a biogeomorphic perspective, using the example of marram grass (Ammophila arenaria) invasion of dune systems in southern New Zealand. The impact of marram grass on dune system dynamics and the underlying archaeological landscape are complex. Full invasion may result in the general burial and protection of these landscapes, but the risk of degradation of sites is high during the invasion process. In southern New Zealand, marram invasion has resulted in the formation of stable foredunes, often associated with coastal progradation. Archaeological sites located close to the shoreline can be subject to either burial or erosion, or both, as marram grass establishes in the foredune zone. The spatial relationship between cultural sites and the shoreline may be lost as the coast progrades. The impact of marram invasion can extend throughout the hinterland dune system as a result of (i) dune mobility triggered by marram grass invasion and (ii) the development of a negative sand budget, which prevents or reduces beach-foredune-dune system sand exchange. The risk of degradation of the archaeological landscape can be significantly heighted by marram invasion, which can have profound implications for the preservation and interpretation of archaeological sites and materials. Paradoxically, dune system restoration may lead to the re-exposure of these sites, but the principal outcome of dune system restoration is expected to be a decline erosion (manifest as in deflation surfaces) and reburial of the archaeological landscape.