The find is believed to be the first evidence of life in the region during the Cretaceous period, a time when the planet was warmer and sea levels were higher.

Monash University palaeontologist Jeffrey Stilwell said for this reason the ancient forest was significant.

''We've never really known what was typical for polar environments when it was a greenhouse Earth,'' he said. ''It's exciting to try and understand this ancient ecosystem, which is really very different from anything today.''

Included in the landscape are large trees preserved in their standing position, early flowering plants, seed cones and insects. Fossilised insects were also found, among them a jewel beetle complete with iridescent shell.

Located 865 kilometres east of Christchurch, the Chatham Islands have been neglected by geologists and palaeontologists because of their remoteness. But after first visiting the islands as a student, Professor Stilwell said he knew there was more there.

''I just had this burning in my gut that there was going to be something really neat there,'' he said.

He returned to the islands with Monash University and Royal Botanic Gardens colleagues and discovered the forest on Pitt Island in February.

Hundreds of fossil samples - many of them embedded in 800 kilograms of rock and shipped back to Monash University - have been collected.

Professor Stilwell said he expected there would be ''scores'' of species new to science among them.

When the forest was preserved after being covered in sediment during a flood, the islands would have been attached to west Antarctica and close to the South Pole.

But far from being covered in ice and snow, the islands were in a high rainfall, temperate environment that was heavily forested.

The environment would have had up to three months of darkness and three months of light a year.

''This is really interesting because these plants and insects were able to alternate between darkness and light … and we don't have any modern analog for this type of forest,'' Professor Stilwell said.

Carbon dioxide levels were also three to six times higher than today. However, while Professor Stilwell said this was evidence that life could adapt and survive in a warmer world, the organisms had ''millennia upon millennia'' to adapt to their environment.

''Today it's happening very quickly,'' he said.

Monash University palaeobotanist Chris Mays said the main types of plants found to date were conifers, ancient flowering plants similar to southern beech trees, and ferns. On average, most trees were between seven and 10 metres tall.

''That tells us this type of forest is a very enduring forest type,'' Dr Mays said. ''And the size of the trees shows they were well established.''