Animals, birds and insects would find shelter and food in the trees, shrubs and grasses.

Then came European settlement.

Now there is only 9per cent of that vegetation left in Western Sydney as threats from sprawling suburbs, agriculture, weed invasion and feral animals take their toll.

In Camden, it is estimated that only 35 square kilometres of Cumberland Plain Woodland survives.

This Sunday's National Tree Day is a chance to take a step towards righting that wrong.

Deb Little, senior horticulturist natural area management at Mount Annan Botanic Garden, said education was pivotal in making people understand the importance of this endangered vegetation.

``It's natural heritage and cultural heritage too, because natural vegetation defines a place as well,'' she said.

``Cumberland Plain Woodland defines this part of Sydney.''

Ms Little said pressure for more land for housing was a major threat to the vegetation.

``We need to think about what sort of housing development and environment we want to have,'' she said.

``Do we want to have to drive to a national park?''

Ms Little said younger generations in particular needed to get a taste of natural bushland.

``If they're the future, if they don't have an environmental ethic they develop early, how is the planet going to survive?'' she asked.

Camden Council's manager of environmentally sustainable design, Adam Wilkinson, said National Tree Day was an excellent opportunity for the council and the community to join in improving the long-term viability of the remnant areas of Cumberland Plain Woodland.

``Increasing both the area and health of Cumberland Plain Woodland remnants will help to ensure the continuing existence of this vegetation community within the Camden local government area,'' he said.

``Planting days provide the community with a greater appreciation of our valuable natural environment.''

Mr Wilkinson said that losing Cumberland Plain Woodland vegetation would mean that the local level of biodiversity would decrease.

``Birds, insects and other animals which depend on these plants and habitats will be negatively affected and will decline proportionally,'' he said. ``By encouraging residents, especially our younger generations, to help restore our local vegetation, they are not only learning to care for our local environment, but we are also ensuring that we will have sustainable, healthy areas of Cumberland Plain Woodland vegetation long into the future.''