Dust is Amazing Stuff
Big things are made up of many small things. That was especially obvious in September 2009 when extreme winds roared across outback Australia, agitating soil laid bare by drought to produce the giant dust storm known as Red Dawn that engulfed eastern Australia, reddening skies from southern NSW to north Queensland, fanning bushfires, damaging crops, delaying planes, halting construction work, triggering smoke alarms, driving up hospital admissions, smearing windows and walls and seeping inside homes to coat floors and furniture in fine powder.
This herculean event, which elicited comparisons with nuclear winter, Armageddon and the planet Mars, swept on to New Zealand, where it sent asthmatics to hospital and dusted alpine snow. In NSW alone the event cost an estimated $330 million in lost topsoil, crop damage, car smashes, worker absenteeism, cleaning and the closure of Sydney Airport.
The particles behind the strife were so small that 100,000 weighed a mere gram, but they rose up in such numbers that Australia managed to lose more than a million tonnes of soil, broadcast into the Tasman Sea and sprinkled over New Zealand. The drama surprised the nation, but Red Dawn was by no means the first onslaught of dust to hit the east coast and it won’t be the last. In the inland, they’re more common: the most recent in Bedourie, western Queensland, when day turned to night last December and dust enveloped the town for more than 90 minutes. Australia is one of the great dust-producing lands, the main source in the southern hemisphere. If Australia faces a drier future, it will be a dustier one as well.
When it enters the sea, dust can make a big difference. The iron that makes our deserts red is a potent fertiliser for plankton, the primary producers in the ocean. Red Dawn wasn’t studied as a fertilising event, but dramatic dust storms in 2002-03 were linked to a drop in carbon dioxide in the atmosphere, which was attributed to plankton taking in more carbon because they were photosynthesising more. So, farmers who flog their paddocks help the fish in the sea by helping the algae that sustain marine life. Some scientists have warned that to plant millions of trees to reduce carbon dioxide could backfire if there is less dust from degraded lands reaching the sea, although that conclusion has been disputed. Australian dust is first-class fertiliser, with 50 per cent more iron than the global average.
Dust comes and goes everywhere. Dust from the Lake Eyre basin – Australia’s dust hot-spot – is thought to reach the Philippines, Antarctica and Patagonia, carried on the prevailing winds. It may well be fertilising Borneo rainforests, just as Saharan dust fertilises the Amazon and central Asian topsoil enriches Hawaii. Like the internet, dust connects the world. New Zealand receives so much dust from Australia – up to 200,000 tonnes in a single event – that Australians go there to study it. Scientists can tell where in Australia the dust comes from by testing which of 25 trace elements it contains; some grains found on Fox Glacier were traced back to Wilcannia in western NSW. Before reaching New Zealand, Australia’s dust grains dance past the smokestacks of coal-fired power stations and mines, acquiring pollutants such as lead, nickel, copper and zinc, which show up on New Zealand glaciers at high enough levels to cause concern. Smoke from bushfires journeys across as well, and spores of wheat rust, a feared disease that ravages whole crops.
[I enjoyed writing this article, which goes on to discuss rain formation, dust mites and other topics, as a change from writing about biology.]