D'harawal educator Frances Bodkin has collated and interpreted the ancient information in her book D'harawal Seasons and Climatic Cycles.

Ms Bodkin said the D'harawal system, which governs almost all of Sydney and interprets plant and animal patterns as signals for changing seasons, was a more reliable predictor for both weather and resource availability than the European system.

There are several cycles in the system, with the longest spanning 12,000 to 20,000 years and the smaller ones running over a few months.

Ms Bodkin, who lives at Tahmoor, said Sydney has just entered ``ngoonungi'', which is the equivalent of spring. ``The flying foxes gather and the waratah blooms are a sign that warm weather is coming,'' she said. ``In the 12-year mudong cycle the most important for the management of natural resources we've reached the end of the cold weather and we'll come into warmer weather but it'll also be wet for about 20 full moons.''

In June, Ms Bodkin held a workshop on the cycles at Mount Annan Botanic Gardens, where she showed participants the sign that winter had arrived male echidnas chasing a female echidna until just one mating male was left standing.

She said Sydney was in the dry, hot part of the ``garawanga'' cycle where there are bushfires every year and the sea level rises.

She said this part of the cycle lasts a few hundred years and in its final phase, South Head near Sydney Harbour will be an island.

Ms Bodkin holds a PhD in indigenous plant medicines and is a post-graduate lecturer at Macquarie University on the environment and at the University of Western Sydney on sociology for indigenous students.

She teaches the D'harawal language at TAFE and also in schools.

A second and third book on the natural resource management of the land will be released next year.