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Core Subject

A 12-metre tube of clay and marine sediment may provide information about Auckland's deforestation by early Polynesian settlers, as well as indicate climate changes, sea level rises and rainfall patterns.

The tube is a core sample taken from the Pukaki crater on Manukau Harbour by a Massey geography post-graduate student, Adam Lancashire. Lancashire is examining the types and amounts of pollen trapped in the core's layers.

"You can get a picture of what the vegetation was like," says Lancashire. As the large trees were cleared, grass pollens became more predominant. By comparing samples from Pukaki with nearby Crater Hill, Lancashire can see which changes were regional and which local. Man-made deforestation occurs over larger areas than natural fires, and evidence of land clearance in New Zealand has been found dating back over 1,000 years.

Lancashire believes his sample covers the last 3,000 years or so, with another 55,000 years of information available dating back to the time of the crater's formation. He'd like to take a look further back at some stage, but admits that he has more than enough material for a host of projects.