As 2023 comes to a close, it will almost certainly become the hottest year on record, forewarning of more unruly weather and rising seas. Throughout New Zealand, coastal communities are already preparing to protect expensive homes and infrastructure from climate change, but dotted along the coastline are thousands of sites that hold a different kind of wealth.
A total of 9054 archaeological sites have been identified within a kilometre of sandy coastlines. Almost all pre-date the arrival of Europeans and include middens, pā sites, urupā and artefact collections where people worked to make adzes and other tools. About half of these sites are within 100m of the shoreline. “And that’s just the sites we know of,” says Benjamin Jones, whose research at the University of Auckland aims to establish which sites are most at risk from sea level rise and coastal erosion.
Jones knows how rich in history such sites are, but also how quickly they can be lost. In October last year, he was excavating a midden that had been exposed in the coastal dunes of Bream Bay, south of Whangārei Harbour. After Cyclone Gabrielle moved through, there was “only a thin lens left of it”.
Working with kaitiaki from the Northland hapū Patuharakeke, Jones and his colleagues are trying to glean as much information as possible before it is too late. “From an archaeological perspective, you can get radiocarbon dates to figure out when that midden was deposited or when people were using that coastal space. The charcoal records give you a vegetation history. The shellfish tell the size of pipi and possibly how they changed over time.”
The hapū is exploring how local accounts weave into the data, bringing mātauranga Māori and research together to tell a more complete story.
For this midden, the team established that it is almost 200 years old but “chronic erosion” has been ongoing for only the past 80 years, moving the shoreline ever closer to the site. In 1942, the midden and the sea were more than 40m apart; by 2020, the distance had shrunk to 3m.
Northland has many places of early occupation and some 40% of sites are at risk, even with a sea level rise of 20cm. The area is part of a nationwide effort to assess the erosion risk for significant places by analysing historical aerial images of coastlines that feature sites registered on the national archaeological database. This delivers a baseline understanding of how coastlines have changed.
Jones then uses a coastal classification index developed by Niwa to assess how sensitive this “national inventory” of archaeological sites will be to erosion and inundation because of sea level rise.
The ultimate goal is to develop a broader strategy to make proactive decisions about eroding sites. “Are we going to excavate 10% of the sites to capture the information that is being lost? Are we going to preserve some of it or are we going to try to protect sites?”
Another conundrum is what should happen with the material that is exposed. This often includes taonga such as adzes or pounamu, Jones says, but museums may not have the capacity to act as repositories.
Eroding urupā raise even more complex issues. A total of 320 coastal burial sites are at risk from rising seas along the coastline, but discussions about their future usually include many groups, from hapū and iwi with whakapapa links to heritage and conservation organisations. Some may advocate for the need to record details and consider moving the site, while others prefer to let the sea take the remains.
