The Ravensthorpe - Hopetoun Region, its environment, biodiversity and ecology

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THE AMAZING PLACE IN WHICH WE LIVE

by Andy Chapman

I’ve been fascinated by the environment around Ravensthorpe since I first came to Fitzgerald River National Park as a crass and uncouth trainee biologist in 1970. Now almost 40 years later it is no coincidence that I’ve spent the majority of my working life here. With very few exceptions all the biological projects I have been involved in here for the last 30 years have revealed biological ‘gold’. That is, a really interesting discovery, for example a species of mammal previously believed to be extinct in WA, a reptile found living here previously only known from somewhere else far away. It might have been how spotted minnows manage to live in our rivers or indeed some aspects of how our rivers work.

But why I find the place so fascinating? One reason is the way the world is and the other relates to the way we have changed the world around us. Let me elaborate. A recent international study identified the south west of WA as one of only 34 sites on earth which have the greatest biological richness or biodiversity. As such it is the only one in Australia. Within the south west are three sub-regional centres of biological richness: Fitzgerald River National Park and Ravensthorpe Range, Stirling Range, and the lateritic hills and sandplains in the vicinity of Jurien Bay. Therefore we live in a localized ‘hotspot’ within a regional ‘hotspot’.

  • Consider the national park; it has approximately 1 700 plant species, this is approximately 20% of the entire flora of WA and more than the entire British Isles and many European countries.
  • Consider the Shire of Ravensthorpe; 535 species of birds have been recorded in WA, of these 203 occur in our shire – that’s nearly 40% of the state total which is a pretty good score by any measure.
  • Consider the Ravensthorpe Range; those who know more about this than I do say more species of eucalypt, that is gum trees and mallees, occur here than any other comparably sized area in Australia.

These are examples of the way the world is – and has been since European settlement. Now consider how we have changed the world in particular the effect of settlement on the flora and fauna of the south west. Many of the rare and endangered species once had distributions far greater than they do today. For example, the western ground parrot, now struggling for survival only in both Fitzgerald River and Cape Arid national parks once occurred on the Swan coastal plain north of Perth and between Albany and Augusta. The heath rat now known from Fitzgerald River National Park, Bandalup Hill, Ravensthorpe Range and Lake Magenta and Dragon Rocks nature reserves once occurred from Shark Bay almost to Eucla. These are but two examples, there are others. What do they have in common? They both occur in the Ravensthorpe Shire. Although the Shire Council may legitimately lament the difficulties of administrating an area which is 65% uncleared bushland this is part of the reason that it is such a biological treasure trove.

The message is clear – the Shire of Ravensthorpe is punching well above its weight as an administrative area with responsibilities to future generations of Australians and indeed the world community for rare and endangered flora and fauna and irreplaceable ecosystems. It is critical that as a community we support conservation initiatives such as Phytopthora dieback and feral predator management and establishing appropriate fire management regimes that take into account the maintenance of plant and animal systems together as well as individual species. Not to do this now, or not to do it to the best of our ability, will see us shamed by future generations, as we are collectively custodians of a priceless and diminished heritage.

Andy Chapman

The above is the text of a brief address, one of several, given at the official opening of Julia Bell’s Eremia Camel Treks on 20 April 2008.  

Andy Chapman is a zoologist living on the edge of the Fitzgerald River National Park, near Ravensthorpe and Hopetoun.

 

Land and Life of the Ravensthorpe Region - a quick history

by Gil Craig

3000 million years ago – volcanic activity around Ravensthorpe caused lava to flow across the surface to form black basalt.  This has weathered to develop the mineral-rich greenstones and fertile, magnesium-rich, red soils around Ravensthorpe.
1000 million years ago  -  Antarctica was against the south coast
-   a mountain range was pushed up on the northern edge of Antarctica
-   an inland sea formed north of the range, then erosion of the Antarctic’s mountain range  washed sediments into the inland sea.  These sediments formed the Mt Barren rocks
-   Antarctica kept pushing in a NW direction, causing the Mt Barren rocks to buckle and fold, tilting the rocks to almost vertical as seen at East Mt Barren
- life = green algae and bacteria in the oceans
250 million years – Australia and Antarctica still joined (Gondwanaland)
-   first conifers and ferns
100 million years – Australia starts splitting from Antarctica
-   first flowering plants and dinosaurs
66 million years ago – early primates appeared along with first Myrtaceae and Banksia-type plants
- about this time our Australian marsupials started to evolve from a South American ancestor which entered Australia
40 million years ago – Antarctica had moved south, severing its links with Australia
-   sea levels were 100 m higher than today and only mountain tops remained exposed, providing island refuges for primitive plants and animals
-   sponges grew in shallow warm seas around the Barren Ranges which eventually formed ‘spongolite’, a useful building material
-  the bench at the seaward base of East Mt Barren is an old sea floor from this time
10 million years ago – Myrtaceae became dominant in rainforest and remained dominant as Australia became increasingly arid 
2-5 million years ago – forest dwindled and herbaceous plants increase
-  dryandras, confined to WA by intervening desert from rest of Australia
-  evolution of birds paralleled the evolution of proteaceous plants.  We now have 203 species of birds recorded in the Ravensthorpe Shire, ie 40% of the state total.  The Fitzgerald Biosphere has 22 native mammals
1-2 million years ago – temperatures and rainfall were very low due to ‘ice ages’
-  during this period many new species formed in the heaths of the South West
-  megafauna reach maximum size – eg diprotodons, a marsupial plant-eater looked a cross between a wombat and a bear and was 2 m high at the shoulder, and a goanna 7 m long!
125,000 years ago –   Ice Age, sea levels 80 m lower than present
-   eucalypts and acacias dominant
56,000 years ago – latest estimate for arrival of first humans in Australia
18,000 years ago – sea level was about 100 m lower than present, temperatures were cooler and ocean water locked in ice caps
-   the rivers were deep valleys and perhaps a lake where Culham Inlet is now and the shoreline was probably out near the continental shelf
-   dunes with shell fragments formed parallel to the shoreline from sand blown up from the ocean floor; this has cemented over time to form limestone
- the limestone has now cut-off lakes and inlets (eg Jerdacuttup Lakes and Culham Inlet)
11,000 years ago – camels became extinct in North America along with 27 other mammal genera
<10,000 years ago – the ice caps melted and seas rose rapidly.  Plant species have been stable for the last 10,000 years due to our climate being relatively stable
6,000 years ago – sea rose to 2 m above its present level
-  Jerdacuttup Lakes were probably an estuarine lagoon with the Jerdacuttup River flowing to the sea
-  shell beds in the inlets show clear evidence of marine conditions
200 years ago -  Europeans arrived to stay
Today – along the coast limestone is being eroded by wave action and forming intertidal platforms (eg Twelve Mile)
-  the younger dunes are steep, irregular, and show evidence of blowouts
-  sea has risen 18 cm since 1900 of which 10 cm occurred in the last 20 years.  At this rate, in 50 years time we’ll be walking Hopetoun’s beaches up to our waists in water!

The Fitzgerald River National Park (FRNP) has approximately 1,660 plant taxa, containing over one quarter (29%) of the south-west’s flora, of which 130 are on the Department of Environment and Conservations’s threatened flora list.
Some of the factors contributing to the park’s biological diversity are:

  1. a complex system of geological and landform types, including the
    - southern edge of Yilgarn granite craton
    - chain of low quartzite mountain ranges
    - a former marine plain
    - upland plains, breakaways, incised river valleys, swamps, lakes, creeks, estuaries and coastal dune systems
  2.  low nutrient levels in the soil
  3. the park being situated between an arid area to the north and east and the wetter area to the west.

The Ravensthorpe Range and FRNP have been recognized as being two of the four areas of highest species richness and having a high degree of local endemics (62 in FRNP and 40 in the Ravenshorpe System) in the State.  The other two are the Stirling Range and Mt Lesueur areas — the flora of the Stirling Range has already been largely compromised by Phytophthora dieback.  Today, the Ravensthorpe Range has 1,300 plant species in 1,000 sq km, making it one of Australia’s most species-rich small areas, notably 62 eucalypts and 50 melaleucas

Gillian Craig
24 January 2010 

 

Gil Craig is a botanist living on a farm near Ravensthorpe.