What Mysterious Event Caused the Demise of the Great Forests?
There is enormous speculation as to what caused the destruction of the kauri forests. Many people have conducted studies all over the northern half of the North Island in the past twenty years or so in order to ascertain the cause of their demise.
The kauri timber and leaves (sometimes from other species) have been preserved in the peat swamps where the chemicals have kept them in almost perfect condition. The locations of the swamps have changed over the years so that different swamps have logs from different dates preserved in them. This adds to the confusion as to what might have happened. In some cases it has been reported by locals that the trees found in their swamps are all lying the same way. This supports the theory that a hurricane or Tsunami was responsible for the destruction in some cases.
Another scenario was presented by a geologist surveying this area about twenty years ago. The study proposed the idea that the Oruanui eruption which occurred 26,500 years ago, may have been a contributing factor to the demise of the last Kauri Forest which grew on this site.
This eruption occurred in the area known as the Volcanic plateau in the centre of the North Island, in and around lake Taupo. The eruption produced over eight hundred cubic kilometres of material which was thrown into the atmosphere. Ash deposits from the eruption have been found all over New Zealand and on some off shore islands.
Could the ash from this cloud have altered the temperature enough to kill off the forests? Perhaps a large tidal wave was produced by the explosion or by an earthquake associated with the eruption. Maybe a meteorite strike caused a blast large enough to flatten the forest. A meteorite strike could also have produced a tidal wave if it hit offshore, as it did after the Mahuika event in the Tasman Sea.
Another theory proposes the sand hills of the west coast have encroached and retreated over the land and have, at times, killed off the forests as the sand smothered the fertile soil. A slight fall in the temperature at that time (to about 5 degrees Celsius cooler than it is now) may also have contributed to the decline as growing conditions became less favourable. Examination of this particular site reveals that the trees that grew and died in this swamp approximately 100,000 years ago lie in all directions and another, less exciting theory, has been put forward to explain the death of this particular forest.
Perhaps nothing cataclysmic happened after all and the trees merely died falling into the swamps naturally. As the swamps increased in size, more trees succumbed to the waterlogged conditions and fell into the swamps on top of others.
Later forests – it appears that there was at least one more – were not preserved because the temperature has increased slightly and the swamps were dry. Debris from the dead trees was merely blown away by the wind.
None of the theories has, as yet proved conclusive so the mystery still remains. Ongoing research of the timber, soil, pollen samples continues and we hope that the study by Dr Ogden and Dr Palmer on this site and other areas around Northland will answer some of these questions.