| | The Natural Area is of State Heritage significance for its environmental heritage with natural, scientific and aesthetic significance for the following reasons:
I) Importance in the evolution of Australian flora, fauna, landscapes and climate.
The "Agnes Banks Sand" is described as a stratigraphic unit of Pliocene of Pleistocene age (7 million-300,000 years ago) and probably a fluvial deposit which has been redistributed by westerly winds. The sands are surrounded by and overlie lateritized tertiary alluvial deposits, mainly clay and silts which make up the Cumberland Plain to the south and east. The sand deposit is unique in that although it is 55km from the present coast, it supports unusual vegetation in many ways similar to coastal sand dune vegetation such as Myall Lakes, and with affinities also to Hawkesbury sandstone vegetation which is located in the Sydney Basin. The deposits themselves are highly important scientifically: as a reference site for understanding the past climatic history of the region; and, for comparison of the vegetation with similar vegetation on coastal sand deposits. The sediment making up the deposit originates from sandstone rock of the Blue Mountains and as such demonstrates the evolutionary process of weathering and deposition.
II) Importance in demonstrating existing processes or natural systems:
The Natural Area supports four distinct associations. These are described as:
i) Low open forest - of Banksia serrata and Angophora bakeri which is confined to the well drained crests of the large dunes;
ii) Woodland - of Eucalyptus sclerophylla, A. bakeri and B. serrata on well-drained and moderately well-drained positions;
iii) Woodland - of E. sclerophylla, E. parramattensis and B. aemula on shallow sand; and
iv) Low-open Woodland - of E. parramattensis which is confined to poorly-drained situations.
Studies by the National Herbarium, Royal Botanic Gardens indicate that species distribution is dominated primarily by a moisture drainage factor which produces a continuum of species. Projective' canopy cover and fire also influence the distribution of the vegetation. The relationship between these environmental factors and vegetation communities is clearly demonstrated at The Natural Area
III. Importance in exhibiting unusual richness or diversity of flora:
The diversity of soil types and conditions has given rise to a corresponding diversity of vegetation types as indicated above.
IV. Importance for rare and endangered or uncommon flora, communities, ecosystems and landscape:
As described in I above, the sand deposits at Agnes Banks are an unusual and rare landform which, in conjunction with vegetation cover, results in a rare landscape type. Areas of original vegetation on the sand deposits associated with the Hawkesbury Nepean River are extremely limited. The area is thus significant as a unique sample of this vegetation, which is otherwise not conserved. The Natural Area support several species which are considered rare or threatened, being represented by small populations, disjunct populations, or being at or near their geographic limits. These include the following:
*Intergrades between Banksia serrata and B. aemula (formerly B. serrati folia ) in parts of portion 157.
* Acacia Bynoena on portion 157 - small populations elsewhere.
* Restio pallens - southern limit at Agnes Banks.
* Persoonia nutans - population on portion 157 is possibly the only surviving location for this species
* Petrophile sessilis northern limit at Agnes Banks, uncommon elsewhere.
* Leucopogon virgatus common at Agnes Banks overall but uncommon in the Nature Reserve.
* Dillwynia tenuifolia small populations, vulnerable in the long term.
* Micromytus minutiflora - as above.
The whole community, with associations relating intergrading with each other, in this isolated inland position, at a low elevation are unique. Likewise is the ecosystem mechanics which operate and determine the species distribution.
V. Importance as representative of the range of ecosystems which characterise sand vegetation type:
More than half of the original sand area of 460 (sic) hectares at Agnes Banks has been cleared or quarried. Only two of the five plant communities recognised on the sand are represented in the existing Nature Reserve. Of the Reserve's 64 hectares only 16 hectares or 3.5% (sic) of the original sand mass is conserved. One of the plant communities - sedgeland - has now been completely destroyed through sand mining operations. The current Agnes Bank Reserve does not sample any Low Open Forest Banksia Serrata and Angophora Bakeri or Woodland E. Sclerophylla, Banksia Serrata and Angophora Baker plant associations. The only other known occurrence of B. Serrata in the general area is a tiny stand on freehold land which is badly damaged. Furthermore, The Natural Area supports other species, namely Persoonia nutans, and Petrophile sessilis, which are not adequately conserved. This inadequate representation of the variation in the system limits the scope of the area for scientific research.
VI. Importance for information contributing to wider understanding of Australian natural history, by virtue of their use as research sites, teaching sites, type localities and reference sites:
i) the isolated location of the deposit makes it suitable for biogeographical studies;
ii) the relationship with the surrounding/underlying clay is of interest as is the internal dynamics controlled by soil water status and fire frequency;
iii) the distinct change in vegetation at the sandclay interface;
iv) the B. aemula/B. serrata interface/hybrid swarm presents a good opportunity for population genetics/autoecological studies;
v) the complex ecotone between plant association of Woodland and Low Woodland;
vi) the site is unusual in geomorphological terms; and
vii) the sands are important as a soil reference site.
Furthermore, as environmental education is a component of school curriculum, the demand for areas such as Agnes Banks for field studies, is great. (Heritage Council Submission to Commission of Inquiry, 1988)
Aboriginal sites already identified at Agnes Banks are believed to date to about 13,000 years ago. Open sites of this age are rare in eastern New South Wales. It is possible that older sites are situated within or under the sand. Agnes Banks may prove to be a significant source of information about human occupation during the late Pleistocene period. |