Over further time and the prevailing south easterly wind the build up of original berm and the merging of mini dunes a green fuzzy ridge of Spinifex and sand, forms a low natural wall of defence against intense invasion from the sea. Behind this wall a snug valley called a swale nurtures conditions for nutrients to accumulate and other specialised plants to further diversify. The salt and wind loving pioneers of the fore dune that helped establish this swale now gives way to new varieties of plants. Low sand holding shrubs like coastal wattle (acacias), banksias with their remarkable predilection for poor soils and accumulating phosphates and adaptations against salt wind and severe dehydration.
Mean while in front of the primary dune new mini dunes continue to form. Over time compounded by the dropping of sea levels they become new primary dunes relegating the original dune to a highly vegetated sand hill called a secondary dune. As sea levels continue to drop over the last glacial period, tertiary dunes form. The original dune has become a coastal forest heathland and it's extended swale a luxurious insect and bird rich heath land.
We must ask ourselves what would happen to the great spread of coastal urban development that have displaced so many sand dunes of their natural barrier systems if a reversal was to occur and sea levels started to rise? From the air a series of parallel beach ridges fringing the seaward edge of many coastal plains indicate a history of coastal advance and sea retreat. The highest sand hill in the world is Mt Tempest of Moreton Island it is 280 metres tall and is in fact a huge transgressive dune.
This whole evolutionary give and take process of dune formation and its protective establishment and sustenance of developing coastal forest is called succession, the journey of the dune. Like the adding and shedding of our skin over time the dunes and sea cliffs form a dynamic living security system that surround our continent. It nurtures the essential feedback processes of homeostasis that keeps coastal terrestrial eco systems in balance enabling them to operate autonomously with relative impunity. Our dune system also alike to the skin is a fragile sensitive organ that functions most effectively within the natural parameters set by it's own evolving tolerance to interference and change.
The coastal forests, heathlands, wetlands and mangroves, sea grasses and salt marshes that this dune succession spawns promotes outgoing sediments of sand and detritus (waste organic matter) which unless contaminated by alien infusions of questionable origin and intent feed the capillaries of it's creek and river systems to fuel the oceans and ultimately refurbish the very basis for it's own continuously recycled and sustained existence.