After flying back from Perth last month, I decided that south-western Australia has more cause to be called an island than Tasmania, if an island is defined as a place where species survive in isolation. Tasmania last had a connection to the mainland about 14,000 years ago, while the South West has been cut from other forested regions by desert for far longer.
The South West stands out from the rest of Australia far more than Tasmania does. It doesn’t share any of its eucalypts with the rest of the country while Tasmania has a large overlap with Victoria. The South West has a few plant families to call its own, Tasmania none. As for special animals, the South West comes far ahead with its honey possum, salamanderfish, Western swamp turtle, red-capped parrot and turtle frog, to name a few. That all of these species are given their own genus is evidence for long isolation. Tasmanian devils and thylacines are very distinctive, but 10, 000 years ago the mainland had them as well.
I visited the South West to appear at the South Coast Festival of Birds in Albany, and to speak to Birdlife Australia in Perth. I used the opportunity to see some wildlife and talk with experts. I was fortunate to spend time in the field with two eminent biologists, Stephen Hopper from the University of Western Australia at Albany, and retired professor John Pate. Steve and John have both written important papers that propose new ways of thinking about plants.
Steve has produced OCBIL Theory, which contrasts very old, climatically buffered, infertile landscapes (OCBILs) with young, often disturbed, fertile landscapes (YODFELs), found mainly in the Northern Hemisphere. His paper on this was important to the first chapter of my bird book, because of statements about south-western heathland plants such as this: “While seed may not disperse often or widely, pollen might through the help of strong-flying animals, notably birds…” One theory about high plant diversity in the South West is that infertility prevents any one domineering species pushing others out. Steve described the South West as region in which it is not easy for plants to go extinct.
The highlight of my trip was Steve showing me Albany pitcherplants. In a family all their own, with trees in South American rainforest as their nearest relatives, they represent completely separate evolution of carnivory in plants. Independently of the typical pitcherplants (Nepenthes) found in north Queensland and elsewhere they evolved a similar pitcher of fluid holding digestive juices protected by a lid. Both types of pitcher plant grow in white sand in boggy places, but their pitchers have different designs. It is presumably because theirs are so short that Albany pitcher plants have jagged teeth on the top of the inside to discourage insects that enter from getting out. Nepenthes, instead of teeth, have pitchers that are so long and curved that the distance inhibits escape.
Steve has a strong interest in Noongar culture, and he showed me the stone traps they made in the past by lifting granite slabs onto small rocks to create enticing refuges for reptile prey. We saw these on the hills above King George Sound, a beautiful body of water in which the Beagle once moored with a young Charles Darwin aboard. I have always been amazed that Darwin could have said about King George’s Sound that “he who thinks with me will never wish to walk again in so uninviting a country”.
This one of the richest regions in the world for wildflowers. But my previous visits to the South West were in spring, and this time, like Darwin, I was there in March, when there are few flowers to catch the eye. In an article I wrote for Australian Geographic many years ago I commented on how obviously homesick Darwin was by the time he reached New Zealand and Australia, hence his sour comments, but now I can better understand how he missed the significance of the plants in the South West.
John Pate has produced a number of valuable books about plant ecology, but what he wanted to talk me through was the Phytotarium concept he has developed with William Verboom. They have amassed evidence indicating that trees play an active role in shaping the soils below by redistributing minerals. At a cutting made into a sand dune near Chillinup Nature reserve, north of Albany, he showed me a layer of clay running horizontally through a quartz sand dune that was produced by wind blowing sand off a nearby dry lakebed.
How did the clay get there? John’s answer is that mallee trees brought the clay minerals up from below the dune and deposited them in a layer. He says that such clay layers can benefit trees by trapping moisture above the clay, for the use of the trees, or by preventing shrubs from reaching water that lies below the clay. He even suggests that some trees bring salt to the upper soil to inhibit competition
We dug up some of the roots of Christmas trees (Nuytsia floribunda), a plant I have written about in the past because of its remarkable features. It has parasitic roots that attach to almost any plant growing nearby, and causes power failures when it taps into buried cables. We found some shiny white haustoria, the attachments it creates to the roots it attacks. John says these slice into the host root with two blades that are so sharp you can cut the inside of your lip on them.
Early one morning at Cheyne’s Beach, during another part of the trip, I glimpsed a pair of noisy scrub-birds skipping across a dirt road. The glimpses were too quick to be very rewarding, but it is difficult to do better with a bird that is as shy as it is endangered. A male will call for hours each day, for much of the year, but from clumps of vegetation that provide no view. For an understanding of global songbird evolution it is one of the most important birds there is, for reasons I go into in my book.
Cheyne’s Beach was one of many places where I saw banksia dying from the introduced disease,Phytophthora. I am used to seeing newly dead banksias on trips to the South West but was nonetheless shocked by how many I saw.
I had an excellent time in the West due to the hospitality of many people, especially Gill Williams, Brad Kneebone, Sue Mather and Basil Schur. I came away with plenty of material for a future book.
