In 2005, when I was chair of the National Committee on Soil and Terrain, I started a debate: where is Australia’s whitest beach? This was a diversion from the committee’s normal business of looking at the sustainable management of Australia’s soils, but it led down a path I hadn’t expected.
What began as a bit of after-hours banter became a serious look across Australia in search of our whitest beaches. New South Wales had already laid claim to the title, arguing that Hyams Beach at Jervis Bay has the whitest sand in the world, purportedly backed up by Guinness World Records.
As it turned out, both claims were false. Guinness World Records has no such category, and the whitest beach (as we found) is actually elsewhere.
So we drafted terms of reference, and the search for Australia’s Whitest Beach began. Over the next year samples were collected across the nation. The criteria were simple: samples had to be taken from the swash zone (the gently sloping area between the water and the dunes) and the samples could not be treated in any way apart from air-drying. No bleaching. No sieving out of impurities. Marine environment only.
The results of the first judging in 2006 were startling. Of all the states and territories, the much promoted Hyams Beach in New South Wales came in fourth. Third was Victoria, second Queensland, and first Western Australia.
The other states and territories came in at Tasmania fifth, Northern Territory sixth, and South Australia seventh. The ACT didn’t have a beach to sample, although technically some of the Commonwealth lands around our coasts could possibly come in under their banner (but that’s another debate altogether).
The winning beach was Lucky Bay in Cape Le Grand National Park on WA’s south coast, but in reality any of the beaches in this area could have been winners – Hellfire Bay, Thistle Cove and Wharton’s beach (just to name a few) are all magnificently white.
A quick qualification here: the southwestern end of Lucky Bay, where many people enter the beach, is covered with seaweed – not the whitest bit! I should also note that all of the finalists in the whitest beach challenge were in their own right fabulously white. But when compared side-by-side, some beaches are clearly whiter than others.
The Queensland team felt aggrieved, so in 2007 I carried out a repechage with new samples from Queensland at Whitehaven Beach in the Whitsundays, and Lake McKenzie on Fraser Island. Lake McKenzie was ultimately disallowed as it is a freshwater lake and the rules stipulated a marine environment. Meanwhile, Whitehaven didn’t quite cut the mustard in the judging and Lucky Bay in WA was again the winner.
The assessments were based on a visual comparison, so to remove any possible visual bias after the 2007 challenge all the samples were scanned for their reflectance – how much light bounced off the sand, essentially – in the visible and infrared wavelengths. Our assumption was that higher reflectance throughout the visual spectrum correlates with greater whiteness.
As it turned out, the results from the scanning exactly correlated with the visual assessments. The eye is quite good at discerning small differences in colour and reflectance. (More background and the results from the competition are available here.)
So what makes a beach white? Obviously, a pristine environment helps. Another factor is the distance from rivers, which deliver coloured organic and clay contaminants to the coast.
The geology of the area and the source of the sand are also critical, with quartz seemingly a major requirement for fine sands. Most white sandy beaches are derived from granitic, or less commonly sandstone, geologies that weather to produce fine, frosted quartz sand grains. Interestingly, sands made from shell or coral fragments just aren’t as white.
While this competition began in fun, I do believe it’s important. Beaches are places of refuge in this crazy world, and a pristine white beach indicates a cleanliness that is worth striving for. The reflectance of light off these sands through shallow waters near the beach creates a surreal, magical turquoise colour. White beaches are like the canary in the coalmine – once they’re spoiled, we know we’re in trouble.
Even though this study was a first look at some of Australia’s whitest beaches, and sampling was limited, it did highlight the sheer number of wonderful sandy beaches that Australia has.
The story’s not finished though. There are many white beaches out there yet to be sampled, and if you’d like to alert me to your potentially award-winning beach please email me or leave a comment on the whitest beach website.
It’s our responsibility, and I believe honour, to protect these amazing places. I’m sure there are more wonderful beaches out there that we haven’t sampled which may defeat Lucky Bay.
Shelburne Bay in northern Queensland, for example, is a contender yet to be sampled, and there are some magnificent beaches on the east coast of Tasmania. Whatever the outcome, let’s celebrate the natural wonders that surround our country.
There’s no doubt that humans killed off the Tasmanian tiger. But a new genetic analysis suggests this species had been on the decline for millennia before humans arrived to drive them to extinction.
The Tasmanian tiger, also known as the thylacine, was unique. It was the largest marsupial predator that survived into recent times. Sadly it was hunted to extinction in the wild, and the last known Tasmanian tiger died in captivity in 1936.
In a paper published in Nature Ecology and Evolution today, my colleagues and I piece together its entire genetic sequence for the first time. It tells us that thylacines’ genetic health had been declining for many millennia before they first encountered human hunters.
Our research also offered the chance to study the origins of the similarity in body shape between the thylacine and dogs. The two are almost identical, despite having last shared a common ancestor more than 160 million years ago – a remarkable example of so-called “convergent evolution”.
Decoding the thylacine genome allowed us to ask the question: if two animals develop an identical body shape, do they also show identical changes in their DNA?
These questions were previously difficult to answer. The age and storage conditions of existing specimens meant that most thylacine specimens have DNA that is highly fragmented into very short segments, which are not suitable for piecing together the entire genome.
We identified a 109-year-old specimen of a young pouch thylacine in the Museums Victoria collection, which had much more intact DNA than other specimens. This gave us enough pieces to put together the entire jigsaw of its genetic makeup.
Next, we made a detailed comparison of thylacines and dogs to see just how similar they really are. We used digital imaging to compare the thylacine’s skull shape to many other mammals, and found that the thylacine was indeed very similar to various types of dog (especially the wolf and red fox), and quite different from its closest living marsupial relatives such as the numbat, Tasmanian devil, and kangaroos.
Our results confirmed that thylacines and dogs really are the best example of convergent evolution between two distantly related mammal species ever described.
We next asked whether this similarity in body form is reflected by similarity in the genes. To do this, we compared the DNA sequences of thylacine genes with those of dogs and other animals too.
While we found many similarities between thylacines’ and dogs’ genes, they were not significantly more similar than the same genes from other animals with different body shapes, such as Tasmanian devils and cows.
We therefore concluded that whatever the reason why thylacines and dogs’ skulls are so similarly shaped, it is not because evolution is driving their gene sequences to be the same.
The thylacine genome also allowed us to deduce its precise position in the marsupial family tree, which has been a controversial topic.
By examining the amount of diversity present in the single thylacine genome, we were able to estimate its effective population size during past millennia. This demographic analysis revealed extremely low genetic diversity, suggesting that if we hadn’t hunted them into extinction the population would be in very poor genetic health, just like today’s Tasmanian devils.
The less diversity you have in your genome, the more susceptible you are to disease, which might be why devils have contracted the facial tumour virus, and certainly why it has been so easily spread. The thylacine would have been at a similar risk of contracting devastating diseases.
This loss in population diversity was previously thought to have occurred as a population of thylacines (and devils) became isolated on Tasmania some 15,000 years ago, when the land bridge closed between it and the mainland.
But our analysis suggests that the process actually began much earlier – between 70,000 and 120,000 years ago. This suggests that both the devil and thylacine populations already had very poor genetic health long before the land bridge closed.
Now that we know the whole genome of the Tasmanian tiger, we know much more about this extinct animal and the unique place it held in Australia’s marsupial family tree. We are expanding our analyses of the genome to determine how it came to look so similar to the dog, and to continue to learn more about the genetics of this unique marsupial apex predator.